A constant current of 0.350 A is passed through an electrolytic cell containing molten CrCl2 for 21.7 h. What mass of Cr(s) is produced

Answers

Answer 1

0.326 grams of Cr(s) is produced when a constant current of 0.350 A is passed through the electrolytic cell containing molten CrCl2 for 21.7 hours.

The production of Cr(s) in the given electrolytic cell can be calculated using Faraday's laws of electrolysis. The first law states that the mass of substance produced during electrolysis is directly proportional to the quantity of electricity passed through the cell. This can be expressed as:

m = Q * M / z * F

Where m is the mass of the substance produced, Q is the quantity of electricity passed through the cell, M is the molar mass of the substance, z is the number of electrons involved in the reaction, and F is the Faraday constant.

In the given case, the quantity of electricity passed through the cell is given as 0.350 A * 21.7 h = 7.595 C. The molar mass of Cr is 52.0 g/mol, and the reaction involves the reduction of Cr3+ to Cr. This reaction involves the transfer of three electrons, so z = 3. The Faraday constant is 96485 C/mol.

Substituting these values into the equation, we get:

m = 7.595 C * 52.0 g/mol / 3 * 96485 C/mol
m = 0.326 g

Therefore, the mass of Cr(s) produced in the given electrolytic cell is 0.326 g.

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Related Questions

a 0.047 m solution of the salt nab has a ph of 9.36. calculate the ph of a 0.011 m solution of hb. (assume kw = 1.00 ✕ 10−14.)

Or, what is the Kb of HB?

Answers

To calculate the pH of a 0.011 m solution of HB, we need to first determine the Kb of HB. HB is a weak base, so we can use the equation Kb = Kw/Ka, where Ka is the acid dissociation constant. Since HB is the conjugate base of the weak acid H2B, we can use the acid dissociation constant of H2B, which is Ka = 1.4 x 10^-9. Therefore, Kb = 7.14 x 10^-6.

Now, we can use the relationship between pH and pOH to determine the pH of the 0.011 m solution of HB. Since pOH = -log[OH-] and [OH-] = sqrt(Kb*[HB]), we can calculate [OH-] as follows:

[OH-] = sqrt(7.14 x 10^-6 * 0.011) = 2.96 x 10^-4 M

And since pH + pOH = 14, we can calculate the pH as:

pH = 14 - pOH = 14 - (-log[OH-]) = 11.53

Therefore, the pH of a 0.011 m solution of HB is approximately 11.53.

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Hexane is commonly used in labs as a solvent for nonpolar compounds. What is the molality of 22.3 mg of vitamin D (C27H44O, 384.6 g/mol) in 50.0 mL of hexane. Hexane has a density of 0.661 g/mL.

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The molality of 22.3 mg of vitamin D in 50.0 mL of hexane is 0.00175 mol/kg.

To calculate the molality of vitamin D in hexane, we need to first convert the mass of vitamin D from milligrams to grams:

22.3 mg = 0.0223 g

Next, we need to calculate the number of moles of vitamin D present in 0.0223 g using its molar mass:

n = m/M = 0.0223 g / 384.6 g/mol = 5.80 x 10⁻⁵ mol

Now, we need to calculate the mass of hexane in the given volume of 50.0 mL using its density:

m = V x d = 50.0 mL x 0.661 g/mL = 33.05 g

Finally, we can calculate the molality of vitamin D in hexane using the formula:

molality = moles of solute / mass of solvent in kg

Since we have the mass of solvent in grams, we need to convert it to kilograms:

mass of solvent = 33.05 g / 1000 = 0.03305 kg

molality = 5.80 x 10⁻⁵ mol / 0.03305 kg = 0.00175 mol/kg

Therefore, the molality of 22.3 mg of vitamin D in 50.0 mL of hexane is 0.00175 mol/kg.

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Determine the pH of a solution prepared by dissolving 0.75 mol of NH3 and 0.25 mol of NH4Cl in a liter of solution. Kb

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i determine the ph of a solution

The pH of the solution is 8.18.

The pH of the solution, we need to first determine the concentration of OH- ions in the solution. We can do this by finding the concentration of NH3 that reacts with water to form OH- ions using the Kb value for [tex]NH_3[/tex].

The reaction between  [tex]NH_3[/tex] and water can be represented as follows:

[tex]NH_3[/tex] + [tex]H_2O[/tex] ⇌ [tex]NH_4[/tex]+ + OH-

The equilibrium constant expression for this reaction is:

Kb = [ [tex]NH_4[/tex]+][OH-] / [ [tex]NH_3[/tex]]

We can use the stoichiometry of the reaction to find the concentration of OH- ions produced by  [tex]NH_3[/tex]:

0.75 mol  [tex]NH_3[/tex] / 1 L solution x 1 L solution = 0.75 M  [tex]NH_3[/tex]

Kb for  [tex]NH_3[/tex] = 1.8 x  [tex]10^{-6[/tex]

[tex]NH_3[/tex] + [tex]H_2O[/tex] ⇌ [tex]NH_4[/tex]+ + OH-

Initially, [ [tex]NH_3[/tex]] = 0.75 M, and [ [tex]NH_4[/tex]+] = [OH-] = 0.

At equilibrium, let x be the concentration of  [tex]NH_4[/tex]+ and OH-. Therefore, the concentration of NH3 remaining at equilibrium will be (0.75 - x) M, and the concentration of OH- ions produced by NH3 will be x M.

Using the Kb expression, we can write:

Kb = [ [tex]NH_4[/tex]+][OH-] / [ [tex]NH_3[/tex]]

1.8 x  [tex]10^{-6[/tex] = x / (0.75 - x)

x = 1.5 x  [tex]10^{-6[/tex] M

Therefore, the concentration of OH- ions produced by  [tex]NH_3[/tex] in the solution is 1.5 x  [tex]10^{-6[/tex] M.

pH = 14 - pOH

pOH = -log[OH-] = -log(1.5 x [tex]10^{-6[/tex]) = 5.82

pH = 14 - 5.82 = 8.18

Therefore, the pH of the solution is 8.18.

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In a particular titration experiment, a 25.0 mL sample of HC 2H 3O 2 requires 30.0 mL of a 0.200 M NaOH solution to reach the equivalence point. What is the concentration of the HC 2H 3O 2

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Therefore, the concentration of the titration [tex]HC_2H_3O_2[/tex] in the sample is 0.240 M.

The balanced chemical equation for the reaction between [tex]HC_2H_3O_2[/tex] is (acetic acid) and NaOH (sodium hydroxide) is:

[tex]HC_2H_3O_2[/tex] i + NaOH → [tex]NaC_2H_3O_2[/tex] + [tex]H_2O[/tex]

From the equation, we can see that the stoichiometric ratio of  [tex]HC_2H_3O_2[/tex]  NaOH is 1:1. This means that the number of moles of NaOH used in the titration is equal to the number of moles of  [tex]HC_2H_3O_2[/tex]  present in the 25.0 mL sample.

We can use the formula:

moles = concentration × volume (in liters)

to calculate the number of moles of NaOH used:

moles NaOH = 0.200 M × 0.0300 L = 0.00600 mol

Since the stoichiometric ratio of  [tex]HC_2H_3O_2[/tex]  to NaOH is 1:1, the number of moles of  [tex]HC_2H_3O_2[/tex]  present in the 25.0 mL sample is also 0.00600 mol.

We can now use the formula above to calculate the concentration of  [tex]HC_2H_3O_2[/tex]:

concentration  [tex]HC_2H_3O_2[/tex]  = moles [tex]HC_2H_3O_2[/tex] / volume (in liters)

The volume of the sample is 25.0 mL, or 0.0250 L:

concentration  [tex]HC_2H_3O_2[/tex]  = 0.00600 mol / 0.0250 L = 0.240 M

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The solutions to the Schrodinger equation for a harmonic oscillator can be applied to diatomic molecules. For atoms with mass mA and mB joined by a bond with a force constant kf, the vibrational frequency is

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The solution to the Schrodinger equation for a harmonic oscillator can be used to determine the energy levels and wave functions of the vibrational motion of a diatomic molecule.

The vibrational frequency (ν) of a diatomic molecule with atoms of masses mA and mB joined by a bond with a force constant kf can be calculated using the formula:

ν = (1/2π) * √(kf / μ)

where μ is the reduced mass of the system, given by:

μ = (mA * mB) / (mA + mB)

The vibrational frequency is related to the energy spacing between the vibrational levels, and can be used to interpret the infrared spectra of diatomic molecules.

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When a 15.8 mL sample of a 0.490 M aqueous hydrocyanic acid solution is titrated with a 0.413 M aqueous sodium hydroxide solution, what is the pH after 28.1 mL of sodium hydroxide have been added?

pH =

When a 28.5 mL sample of a 0.460 M aqueous nitrous acid solution is titrated with a 0.395 M aqueous potassium hydroxide solution, what is the pH at the midpoint in the titration?

pH =

A 16.0 mL sample of a 0.374 M aqueous acetic acid solution is titrated with a 0.351 M aqueous barium hydroxide solution. What is the pH at the start of the titration, before any barium hydroxide has been added?

pH =

Answers

For the first question:

Write the balanced chemical equation for the reaction between hydrocyanic acid (HCN) and sodium hydroxide (NaOH):

HCN + NaOH → NaCN + H2O

Calculate the initial number of moles of HCN in the solution:

n(HCN) = M(HCN) x V(HCN) = 0.490 M x 0.0158 L = 0.007742 mol HCN

Determine which reactant is the limiting reactant:

n(NaOH) = M(NaOH) x V(NaOH) = 0.413 M x 0.0281 L = 0.01162 mol NaOH

Based on this calculation, NaOH is in excess and HCN is the limiting reactant.

Calculate the number of moles of HCN remaining after the reaction is complete:

n(HCN) = n(initial) - n(NaOH) = 0.007742 mol - 0.01162 mol = -0.003878 mol

Note that this is a negative value, which means that all of the HCN has been consumed and there is excess NaOH remaining.

Calculate the concentration of NaOH remaining in the solution:

M(NaOH) = n(NaOH) / V(total)

V(total) = V(HCN) + V(NaOH) = 0.0158 L + 0.0281 L = 0.0439 L

M(NaOH) = 0.01162 mol / 0.0439 L = 0.264 M

Calculate the concentration of hydroxide ions in the solution:

[OH-] = M(NaOH) x (V(NaOH) / V(total)) = 0.264 M x (0.0281 L / 0.0439 L) = 0.169 M

Calculate the pOH of the solution:

pOH = -log[OH-] = -log(0.169) = 0.771

Calculate the pH of the solution:

pH + pOH = 14.00

pH = 14.00 - pOH = 14.00 - 0.771 = 13.229

Therefore, the pH of the solution after 28.1 mL of NaOH have been added is 13.229.

For the second question:

Write the balanced chemical equation for the reaction between nitrous acid (HNO2) and potassium hydroxide (KOH):

HNO2 + KOH → KNO2 + H2O

Calculate the initial number of moles of HNO2 in the solution:

n(HNO2) = M(HNO2) x V(HNO2) = 0.460 M x 0.0285 L = 0.01311 mol HNO2

Determine the volume of KOH required to reach the midpoint of the titration:

At the midpoint of the titration, half of the HNO2 has been converted to NO2-. Therefore, the number of moles of KOH required to reach this point is equal to half the initial number of moles of HNO2:

n(KOH) = 0.5 x n(HNO2) = 0.5 x 0.01311 mol = 0.006556 mol KOH

The volume of KOH required can be calculated using the concentration of KOH:

V(KOH) = n(KOH) / M(KOH) = 0.006556 mol / 0.395 M = 0.

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13) What is the final concentration of a solution prepared by using 75.0 mL of 18.0 M H2SO4 to prepare 500. mL of solution

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The final concentration of the solution is 2.7 M H₂SO₄

We can use the formula:

M1V1 = M2V2

where M1 is the initial concentration, V1 is the initial volume, M2 is the final concentration, and V2 is the final volume.

In this case, we know that the initial volume (V1) is 75.0 mL and the initial concentration (M1) is 18.0 M. We also know that the final volume (V2) is 500.0 mL.

To find the final concentration (M2), we can rearrange the formula:

M2 = (M1V1) / V2

Plugging in the numbers, we get:

M2 = (18.0 M * 75.0 mL) / 500.0 mL

M2 = 2.7 M

Therefore, the final concentration of the solution is 2.7 M.

Thus, we can find the final concentration of a solution by using the formula M1V1 = M2V2 and rearranging it to solve for M2. In this specific problem, the final concentration is 2.7 M when 75.0 mL of 18.0 M H2SO4 is used to prepare 500.0 mL of solution.

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What is the name of the enzyme that catalyzes the reaction where the third carbon (C3) of glucose is converted to CO2. Imagine that the C3 of glucose is isotopically labeled (13C) and follow the carbon through the reactions of glycolysis, PDH, and TCA where applicable.

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The enzyme that catalyzes the reaction where the third carbon (C₃) of glucose is converted to CO₂ is pyruvate dehydrogenase (PDH). PDH is a multi-enzyme complex that converts pyruvate (a three-carbon molecule) to acetyl-CoA (a two-carbon molecule), releasing CO₂ and producing NADH in the process.

If the C₃ of glucose is isotopically labeled with 13C, it will be incorporated into the pyruvate molecule during glycolysis. This labeled pyruvate will then be converted to labeled acetyl-CoA by PDH, with the labeled carbon atom being released as CO₂. The labeled carbon will then be incorporated into the TCA cycle through the formation of citrate, and it will undergo a series of oxidation-reduction reactions before ultimately being released as CO₂ in the final step of the cycle.

Overall, the labeled carbon will be released as CO₂ twice during the metabolism of glucose: once during PDH and once during the TCA cycle. The fate of the labeled carbon can be traced through the metabolic pathways using isotopic labeling techniques such as isotopic tracer analysis.

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Which structures are composed of aqueous compartments enclosed by a lipid bilayer and can be used to deliver chemicals to cells?a. vesicleb. micellec ribosomed. chloroplaste lysosome

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The structures that are composed of aqueous compartments enclosed by a lipid bilayer and can be used to deliver chemicals to cells are vesicles and micelles. The correct option is A and B.

Vesicles are small sacs made up of a lipid bilayer membrane that encloses an aqueous compartment, and they are involved in various cellular processes such as transport, secretion, and storage. These structures can be used to deliver chemicals to cells by fusing with the cell membrane and releasing their contents into the cell.

Micelles, on the other hand, are small spherical aggregates of amphipathic molecules such as lipids, detergents, or surfactants that form a lipid bilayer-like structure in water. They are also used to deliver chemicals to cells by facilitating the transport of hydrophobic molecules across the cell membrane. Micelles can solubilize hydrophobic drugs and help them penetrate the cell membrane, making them an effective drug delivery system.

Ribosomes and chloroplasts are not enclosed by a lipid bilayer and are not involved in the delivery of chemicals to cells. Lysosomes are also enclosed by a lipid bilayer but are involved in the breakdown and recycling of cellular waste, rather than delivering chemicals to cells.

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24.60 mL of 0.1852 M HNO3 is titrated to the phenolphthalein end point with 27.35 mL of a KOH solution. What is the molarity of the KOH solution

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The  molarity of the KOH solution is 0.1647 M when titrated to the phenolphthalein end point with 27.35 mL of a KOH solution.

To arrive at this answer, we can use the balanced chemical equation for the reaction between [tex]HNO_{3}[/tex] and KOH:
[tex]HNO_{3} + KOH -> KNO_{3}+ H_{2}O[/tex]
We can see that the reaction is a 1:1 ratio, which means that the moles of [tex]HNO_{3}[/tex] that reacted is equal to the moles of KOH that reacted.
First, we need to calculate the moles of [tex]HNO_{3}[/tex] that reacted:
moles [tex]HNO_{3}[/tex]= M x V

= 0.1852 M x 0.02460 L

= 0.00455 moles
Since the moles of KOH that reacted is equal to the moles of [tex]HNO_{3}[/tex] that reacted, we can use the moles of [tex]HNO_{3}[/tex] to calculate the molarity of the KOH solution:
moles KOH = moles [tex]HNO_{3}[/tex] = 0.00455 moles
molarity KOH = moles KOH / V

= 0.00455 moles / 0.02735 L

= 0.1647 M
The molarity of the KOH solution is 0.1647 M.

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When supercooled droplets freeze directly to very cold surfaces and create fine, needle-like ice crystals, the result is:

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When supercooled droplets freeze directly to very cold surfaces and create fine, needle-like ice crystals, the result is called diamond dust.

Supercooled droplets are liquid droplets that are at a temperature below their normal freezing point, but have not yet frozen due to the absence of a nucleation site or trigger for freezing. When these droplets come into contact with a very cold surface, such as a car windshield or tree branch, they can freeze instantly and form tiny ice crystals.

These ice crystals are typically very small, with diameters of less than 0.5 millimeters, and take on a needle-like or columnar shape. They can accumulate on surfaces to form a thin layer of ice, creating a beautiful and sparkling effect that resembles diamond dust.

Freezing fog and diamond dust are most commonly observed in cold, dry climates, such as polar regions or high-altitude mountain ranges. They can create hazardous conditions for travel, as they can make surfaces slippery and reduce visibility, but they can also be a beautiful and awe-inspiring natural phenomenon to witness.

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Calculate the pH of each of the following solutions. (a) 7.9 × 10−4 M Ba(OH)2: =__× 10 (Enter your answer in scientific notation.) (b) 8.5 × 10−4 M HNO3:

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(a) To calculate the pH of a solution, we need to first determine the concentration of hydrogen ions (H+). For a strong base like Ba(OH)2, we can assume that it dissociates completely in water, yielding two hydroxide ions (OH-) for every one molecule of Ba(OH)2. Therefore, the concentration of OH- in the solution would be 2 times the concentration of Ba(OH)2, which is 1.58 × 10^-3 M (7.9 × 10^-4 M × 2).

Next, we can use the equation for the dissociation of water (Kw = [H+][OH-]) to solve for the concentration of H+ ions:

Kw = [H+][OH-]
1.0 × 10^-14 = [H+][1.58 × 10^-3]
[H+] = 6.33 × 10^-12 M

Finally, we can use the equation for pH (pH = -log[H+]) to find the pH of the solution:

pH = -log(6.33 × 10^-12) = 11.2

Therefore, the pH of a 7.9 × 10^-4 M Ba(OH)2 solution is 11.2.

(b) For a strong acid like HNO3, we can assume that it dissociates completely in water, yielding one hydrogen ion (H+) for every one molecule of HNO3. Therefore, the concentration of H+ in the solution would be equal to the concentration of HNO3, which is 8.5 × 10^-4 M.

Next, we can use the equation for pH (pH = -log[H+]) to find the pH of the solution:

pH = -log(8.5 × 10^-4) = 3.07

Therefore, the pH of an 8.5 × 10^-4 M HNO3 solution is 3.07.

In summary, the pH of a solution can be calculated using the concentration of H+ or OH- ions in the solution, depending on whether it is an acid or a base. For a strong acid or base, we can assume complete dissociation in water, making the calculation straightforward.

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an unlisted radioactive substance has a half-life of 10,000 years. in 20,000 years, how much (percentage) of the original substance will remain

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If the half-life of the radioactive substance is 10,000 years, then in 10,000 years half of the original substance will have decayed.

This means that after 20,000 years, two half-lives will have passed, and only 25% of the original substance will remain (50% after the first half-life, and 50% of that remaining 50% after the second half-life). So, 25% of the original substance will remain after 20,000 years.

Here's a step-by-step explanation to find the percentage of the original substance remaining after 20,000 years:
1. Determine the half-life of the radioactive substance: In this case, the half-life is 10,000 years.
2. Calculate how many half-lives have passed in the given time period: 20,000 years / 10,000 years per half-life = 2 half-lives.
3. Determine the fraction of the original substance remaining after each half-life: Since half of the substance decays after each half-life, the fraction remaining after one half-life is 1/2 (50%).
4. Calculate the fraction of the original substance remaining after the given number of half-lives: (1/2) ^ 2 (two half-lives) = 1/4 (25%).

So after 20,000 years, 25% of the original radioactive substance will remain.

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A mixture of the amino acids leucine (Leu), glutamate (Glu), and arginine (Arg) is added to a cation exchange column at neutral pH. In what order will they elute from a cation exchange column

Answers

The order of elution for the given amino acids from a cation exchange column at neutral pH is: Leu, Glu, Arg.

The elution order of amino acids from a cation exchange column depends on the net charge of the amino acid at the pH of the elution buffer. At neutral pH, the carboxyl group (-COOH) of amino acids is not fully ionized, while the amino group (-NH3+) is fully ionized, resulting in a net positive charge for the amino acid.

Among the given amino acids, leucine (Leu) is a nonpolar amino acid and does not have any ionizable side chains. Therefore, it does not have any net charge at neutral pH and will not bind to the cation exchange column. It will pass through the column and elute first.

Arginine (Arg) is a basic amino acid with a positively charged guanidinium group (-NH=C(NH2)2) in its side chain. At neutral pH, the guanidinium group is fully ionized, resulting in a net positive charge. Therefore, Arg will bind to the cation exchange column through ionic interactions and will elute last.

Glutamate (Glu) is an acidic amino acid with a negatively charged carboxyl group (-COO-) in its side chain. At neutral pH, the carboxyl group is only partially ionized, resulting in a net negative charge. Therefore, Glu will have a weaker interaction with the cation exchange column compared to Arg and will elute in between Leu and Arg.

Therefore, the order of elution for the given amino acids from a cation exchange column at neutral pH is: Leu, Glu, Arg.

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My reaction calls for 20 mol% of catalyst. If I use 15 mmol of limiting reagent, how many mmol of catalyst should I be using

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If your reaction calls for 20 mol% of catalyst and you are using 15 mmol of limiting reagent, you would need to use 3 mmol of catalyst.

To calculate this, first you need to convert the 20 mol% into a decimal fraction by dividing it by 100, which gives you 0.2.

Then, you can calculate the total amount of moles needed for the reaction by multiplying the limiting reagent (15 mmol) by the stoichiometric coefficient of the catalyst in the balanced chemical equation.

For example, if the catalyst has a coefficient of 2, then you would need a total of 30 mmol of catalyst for the reaction. Finally, you can multiply the total amount of catalyst needed by the percentage required (0.2) to find out how much you should use for your specific reaction. In this case, 30 mmol x 0.2 = 6 mmol, which is the total amount of catalyst required.

Since you only need 20 mol% of this amount, you would use 3 mmol of catalyst for the reaction.

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(0/2pts) Concentration of Ca2 (M) 0.01971 Saved (0/2pts) Value of Ksp 3.063e-5 Saved (0/2pts) What is the molar solubility of Ca(OH)2 in pure water

Answers

The molar solubility of [tex]Ca(OH)_2[/tex] in pure water is 0.00414 M.

To find the molar solubility of the  [tex]Ca(OH)_2[/tex]  in pure water, we can use the Ksp expression:

Ksp =[tex][Ca_2+][OH-]^2[/tex]

Since [tex]Ca(OH)_2[/tex] dissociates to form one [tex]Ca_2+[/tex]ion and two OH- ions, we can write:

Ksp =[tex][Ca_2+][OH-]^2 = (s)(2s)^2 = 4s^3[/tex]

where s is the molar solubility of [tex]Ca(OH)_2[/tex].

Substituting the given value of Ksp and solving for s, we get:

3.063e-5 = [tex]4s^3[/tex]

s = 0.00414 M

Therefore, the molar solubility of [tex]Ca(OH)_2[/tex] in the pure water is 0.00414 M. This means that at equilibrium, the concentration of [tex]Ca_2+[/tex] ion and OH- ion will be 0.00414 M, while the remaining [tex]Ca(OH)_2[/tex] will be in the solid state.

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The molar solubility of Ca(OH)₂ in pure water is approximately 0.00726 M.

What is solubility product?

The solubility product is a type of equilibrium constant whose value varies with temperature. Ksp typically rises as temperature rises due to greater solubility.

The solubility product constant (Ksp) expression for calcium hydroxide (Ca(OH)₂) in water is:

Ksp = [Ca²⁺][OH⁻]²

Where [Ca²⁺] is the molar concentration of dissolved Ca²⁺ ions, and [OH⁻]] is the molar concentration of dissolved OH⁻] ions.

Since calcium hydroxide dissociates into one calcium ion and two hydroxide ions in water, we can write:

Ca(OH)2 (s) ⇌ Ca²⁺ (aq) + 2 OH⁻] (aq)

At equilibrium, the concentrations of Ca²⁺ and OH⁻] are related to the molar solubility (S) of Ca(OH)₂ as follows:

[Ca²⁺] = S

[OH⁻]] = 2S

Substituting these expressions into the Ksp expression gives:

Ksp = S * (2S)²

Simplifying this expression gives:

Ksp = 4S³

Solving for S gives:

S = [tex](Ksp/4)^{(1/3)[/tex]

Substituting the given values for Ca²⁺ concentration and Ksp, we get:

S = [tex]((3.063e-5)/4)^{(1/3)[/tex]

S = 0.00726 M

Therefore, the molar solubility of Ca(OH)₂ in pure water is approximately 0.00726 M.

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Now the engineering students have placed a 50 kg lump of copper at 140 C into an insulated tank containing 90 L of water. The initial temperature of the tank was 10 C. What is the entropy change of the copper for this process in kJ/K

Answers

The mass of the copper is 50 kg and the change in temperature (ΔT) is 130 C (140 C - 10 C). Therefore, the entropy change of the copper is 6.5 kJ/K (50 kg × 130 C × 0.05 kJ/K).

What is copper ?

Copper is a soft, malleable, and ductile metal that is naturally found in the Earth's crust. It is an essential element for all forms of life, and it is used in a variety of ways in the modern world. Copper is one of the oldest metals used by humans and has been used for thousands of years in the production of jewelry, coins, and statues. It is also used in the production of electrical wiring, plumbing pipes, and other components used in the construction of buildings. Copper is also used in many industrial applications, such as in the production of semiconductors, motors, and other electronic components.

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What is the pressure of a gas, in millimeters of mercury, in a sample container connected to a mercury-filled, open-ended manometer if the level of mercury in the arm connected to the atmosphere is 3.41 cm higher than the arm connected to the sample container and if atmospheric pressure is 99.54 kPa

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The  pressure of the gas in the sample container connected to the manometer is 25.6 mmHg. First, we need to convert the height difference of the mercury levels from centimeters to millimeters. There are 10 mm in 1 cm, so the height difference is 3.41 cm x 10 mm/cm = 34.1 mm.

We need to find the pressure difference between the gas in the sample container and the atmospheric pressure. This can be found by subtracting the height difference of the mercury levels from the atmospheric pressure. 99.54 kPa - (34.1 mm / 760 mmHg/kPa) = 99.54 kPa - 0.045 = 99.495 kPa ,Now we can use the conversion factor of 1 mmHg = 0.133 kPa to convert the pressure difference from kilopascals to millimeters of mercury. 99.495 kPa x (1 mmHg/0.133 kPa) = 748.5 mmHg .


First, convert the atmospheric pressure from kPa to mmHg. 1 kPa is approximately equal to 7.50062 mmHg. So, 99.54 kPa × 7.50062 (mmHg/kPa) ≈ 746.99 mmHg. Convert the difference in mercury levels from cm to mm. 1 cm is equal to 10 mm. So, 3.41 cm × 10 (mm/cm) = 34.1 mm. The level of mercury in the arm connected to the atmosphere is 3.41 cm higher than the arm connected to the sample container, meaning the gas pressure is lower than the atmospheric pressure. Subtract the difference in mercury levels from the atmospheric pressure to find the gas pressure: 746.99 mmHg - 34.1 mm = 726.4 mmHg.
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An aqueous solution of hydroiodic acid is standardized by titration with a 0.119 M solution of barium hydroxide. If 13.2 mL of base are required to neutralize 26.5 mL of the acid, what is the molarity of the hydroiodic acid solution

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The molarity of the hydroiodic acid solution is 0.059 M.

The balanced chemical equation for the reaction between hydroiodic acid (HI) and barium hydroxide (Ba(OH)2) is:

2HI + Ba(OH)2 → BaI2 + 2H2O

From the equation, we can see that 2 moles of HI react with 1 mole of Ba(OH)2.

Given that 13.2 mL of 0.119 M Ba(OH)2 is required to neutralize 26.5 mL of hydroiodic acid, we can set up the following equation:

0.119 M Ba(OH)2 x 13.2 mL = M HI x 26.5 mL

Solving for the molarity of hydroiodic acid:

M HI = (0.119 M Ba(OH)2 x 13.2 mL) / 26.5 mL

= 0.059 M

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In a particular electroplating process, the metal being plated has a 3 charge. If 648.2 C of charge pass through the cell, how many moles of metal should be plated

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0.006711 moles of metal should be plated in the given electroplating process.
To determine how many moles of metal should be plated in the given electroplating process, we need to use Faraday's law of electrolysis.


Faraday's law states that the amount of substance produced at an electrode during electrolysis is directly proportional to the amount of electrical charge passed through the cell. This can be expressed by the following equation:

mol of substance = (charge passed / Faraday's constant) x oxidation state of substance

where,
- charge passed is the electrical charge in Coulombs (C)
- Faraday's constant is the charge per mole of electrons (96485 C/mol)
- oxidation state is the charge on the metal being plated

Using the given values, we can plug them into the equation as follows:

mol of metal = (648.2 C / 96485 C/mol) x 3

mol of metal = 0.006711 mol

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A chemistry graduate student is given of a trimethylamine solution. Trimethylamine is a weak base with . What mass of should the student dissolve in the solution to turn it into a buffer with pH

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To turn the trimethylamine solution into a buffer with a desired pH, the chemistry graduate student needs to add a conjugate acid to the solution. The conjugate acid of trimethylamine is trimethylammonium ion (CH3)3NH+.

First, the student needs to calculate the pKa of trimethylamine using the given Ka value:

Ka = [H+][CH3NH2]/[CH3NH3+]
pKa = -log(Ka)
pKa = -log(4.4 × 10^-10)
pKa = 9.36

Next, using the Henderson-Hasselbalch equation, the student can calculate the ratio of [CH3NH2]/[CH3NH3+] needed to achieve the desired pH:

pH = pKa + log([base]/[acid])
7.4 = 9.36 + log([CH3NH2]/[CH3NH3+])
log([CH3NH2]/[CH3NH3+]) = -1.96
[CH3NH2]/[CH3NH3+] = 0.010 ^ (-1.96)
[CH3NH2]/[CH3NH3+] = 0.014

Now, we can assume that the final volume of the solution remains constant, and use the equation of moles = concentration × volume to calculate the moles of trimethylamine (base) and trimethylammonium ion (acid) required to obtain the desired buffer solution:

Let's assume we need to prepare 1 L of buffer solution.
Assume that the initial trimethylamine solution has a concentration of 0.1 M (just for an example).
We need to determine the amount (in moles) of base (trimethylamine) and acid (trimethylammonium ion) needed to make the buffer solution.

Moles of base (trimethylamine) needed:
moles of base = concentration × volume
moles of base = 0.1 M × 1 L × 0.014
moles of base = 0.0014 moles

Moles of acid (trimethylammonium ion) needed:
moles of acid = concentration × volume
moles of acid = 0.1 M × 1 L × (1 - 0.014)
moles of acid = 0.086 moles

Now, the student needs to calculate the mass of trimethylammonium chloride (the conjugate acid of trimethylamine) needed to provide the required amount of trimethylammonium ion:

molar mass of (CH3)3NHCl = 109.64 g/mol
mass of (CH3)3NHCl = moles of acid × molar mass of (CH3)3NHCl
mass of (CH3)3NHCl = 0.086 moles × 109.64 g/mol
mass of (CH3)3NHCl = 9.49 g

Therefore, the chemistry graduate student needs to dissolve 9.49 g of trimethylammonium chloride in the trimethylamine solution to obtain a buffer with pH 7.4.
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l Jtudell conducted the following reactions: Nis)+Pb black crystals formed and the Ni solid disintegrated Ni(s)+Fe No rxn a. Write the net ionic equations for both of these reactions, gving the "possible"F the second reaction. b. Rank the three metals: Ni, Pb, and Fe based on these 2 reactions. c. Where would Ni be placed on your activity series? 6. A student conducted the following reactions: Ni(s)+Co dark crystals formed and the Ni solid disintegrated Co(s)+N dark crystals formed and the Co solid disintegrated Explain why the student should have immediately known that something was wrong a repeated the tests. Conclusion: Summarize the purpose of the lab, including what an activity series shows. List your activity series. Discuss discrepancies between your activity series and the correct activity these metals. Suggest improvements to the lab. expo

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In the first reaction, The net ionic equation for the reaction is: Ni(s) + Pb²⁺(aq) → Ni²⁺(aq) + Pb(s)
In the second reaction, Ni(s) reacts with Fe but no reaction occurs.

Based on these reactions, we can rank the three metals in the following order of reactivity: Ni > Pb > Fe. This is because Ni is reactive enough to displace Pb, but not reactive enough to displace Fe. Ni would be placed above Pb and below Fe in the activity series. In the student's experiment, Ni(s) reacts with Co to form dark crystals and disintegrates, and Co(s) reacts with N to form dark crystals and disintegrate. The student should have known that something was wrong since both Ni and Co cannot displace each other in their respective reactions. This indicates an error in the experiment or an impurity in the reactants.

The purpose of this lab is to determine the activity series of metals, which shows the reactivity of metals in decreasing order. The activity series is useful in predicting the outcomes of single displacement reactions. Based on the given data, the activity series is Ni > Pb > Fe. To improve the lab, ensure the purity of reactants and use accurate measuring tools. Additionally, conduct more tests with different metals to confirm the activity series and account for any discrepancies.

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Explain in terms of Coulomb's law why a polar molecule is attracted to both positive and negative charges.

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Coulomb's law states that the force of attraction or repulsion between two charged particles is directly proportional to the product of their charges and inversely proportional to the distance between them squared.

A polar molecule has a partial positive charge on one end and a partial negative charge on the other end due to the uneven distribution of electrons within the molecule. These partial charges create an electric dipole moment. When the polar molecule approaches a positively charged particle, the negative end of the molecule is attracted to the positive charge, and vice versa when it approaches a negatively charged particle. The force of attraction between the partial charges on the polar molecule and the opposite charges on the particle is governed by Coulomb's law. Therefore, a polar molecule is attracted to both positive and negative charges because of the electrostatic force of attraction that exists between them.
Coulomb's Law states that the force between two charged particles is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. A polar molecule has a partial positive charge on one end and a partial negative charge on the other end due to the unequal distribution of electrons.

When a polar molecule is near a positive charge, the negative end of the molecule is attracted to the positive charge, while the positive end is repelled. Conversely, when the polar molecule is near a negative charge, the positive end is attracted to the negative charge, and the negative end is repelled. This attraction between the polar molecule and both positive and negative charges is due to the interaction of the charges according to Coulomb's Law.

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A gas cylinder containing 6.38 mol of neon has a pressure of 491 mm Hg at 295 K. If 3.22 mol of helium is added to this cylinder, at constant temperature and volume, what will be the pressure in the cylinder

Answers

The pressure in the cylinder after adding the helium is 0.873 atm.

We can use the ideal gas law to solve this problem. The ideal gas law states that:

PV = nRT

Since the temperature and volume of the gas are constant, we can simplify the ideal gas law to:

P1V = n1RT

P2V = (n1 + n2)RT

where P1 is the initial pressure of the gas, n1 is the initial number of moles of gas (6.38 mol of neon), n2 is the number of moles of gas added (3.22 mol of helium), and P2 is the final pressure of the gas.

P2 = (n1 + n2)RT/V

   = [(6.38 mol) + (3.22 mol)] * (0.0821 L*atm/mol*K) * (295 K) / V

   = 9.60 atm / V

To find V, we can use the fact that the volume is constant:

P1V = P2V

V = P1V/P2

 = (491 mm Hg) * (1 atm/760 mm Hg) * (22.4 L) / (9.60 atm)

 = 11.0 L

Now we can substitute V = 11.0 L into the expression for P2:

P2 = 9.60 atm / 11.0 L

   = 0.873 atm

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A 1.65 g sample of an unknown gas at 352 K and 1.00 atm is stored in a 1.95 L flask. What is the density of the gas

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The density of the unknown gas is approximately 0.846 g/L, calculated using its mass, volume, temperature, and pressure, and the ideal gas law. The molar mass of the gas was also calculated to be approximately 43.74 g/mol.

To calculate the density of the unknown gas, we can use the following formula:
Density = mass / volume
Given:
Mass = 1.65 g
Volume = 1.95 L
Temperature = 352 K
Pressure = 1.00 atmFirst, we need to convert the mass to moles using the Ideal Gas Law:PV = nRT
Where:
P = pressure (1.00 atm)
V = volume (1.95 L)
n = number of moles (unknown)
R = gas constant (0.0821 L·atm/mol·K)
T = temperature (352 K)
1.00 atm * 1.95 L = n * 0.0821 L·atm/mol·K * 352 K
n = 1.65 g / molar mass (unknown)Rearranging the equation for molar mass:
Molar mass = (1.65 g) / (1.00 atm * 1.95 L) * (0.0821 L·atm/mol·K * 352 K)
Molar mass ≈ 43.74 g/mol
Now, we can find the density:
Density = (1.65 g) / (1.95 L)
Density ≈ 0.846 g/L
The density of the unknown gas is approximately 0.846 g/L.

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What reaction conditions favor the conversion of the initially-formed salt to the amide when an amine and a carboxylic acid are reacted with each other

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To favor the conversion of the initially-formed salt to the amide when an amine and a carboxylic acid are reacted with each other, you should use the following reaction conditions:

1. Apply heat: Heating the reaction mixture helps promote the formation of the amide by driving off the water formed in the reaction.

2. Use a coupling agent: Adding a coupling agent like DCC (dicyclohexylcarbodiimide) or EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide) can facilitate the formation of the amide by activating the carboxylic acid group and making it more reactive.

3. Opt for a non-aqueous solvent: Using a non-aqueous solvent, such as an aprotic solvent like DMF (dimethylformamide) or DCM (dichloromethane), helps prevent the reverse reaction (hydrolysis of the amide) and promotes the formation of the desired product.

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If an excess of a compound that reacts with primary amines were introduced to a cell, how would the activity of newly synthesized pyruvate carboxylase be affected

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If an excess of a compound that reacts with primary amines were introduced to a cell, it could potentially lead to a decrease in the activity of newly synthesized pyruvate carboxylase.

What is pyruvate carboxylase?

Pyruvate carboxylase is an enzyme that plays a key role in the metabolism of carbohydrates and fats. It catalyzes the conversion of pyruvate, a three-carbon molecule produced during glycolysis, into oxaloacetate, a four-carbon molecule. This reaction requires the presence of ATP and bicarbonate, and it occurs in the mitochondria of cells.

What is primary amines?

Primary amine is an organic compound that contains a nitrogen atom attached to two hydrogen atoms and one alkyl or aryl group.

According to the given information:

If an excess of a compound that reacts with primary amines were introduced to a cell, it could potentially lead to a decrease in the activity of newly synthesized pyruvate carboxylase. Pyruvate carboxylase contains lysine residues that are critical for its activity, and excess amounts of a compound that reacts with primary amines could potentially modify or inhibit these lysine residues, thereby reducing the activity of the enzyme. Additionally, excess amounts of the compound could lead to the accumulation of toxic byproducts, which could further disrupt cellular processes and lead to a decrease in pyruvate carboxylase activity. Overall, the exact effect of the compound on pyruvate carboxylase activity would depend on the specific nature and concentration of the compound, as well as the overall metabolic state of the cell and the availability of other cellular components necessary for pyruvate carboxylase function.

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The work functions of four different metals M1, M2, M3, and M4 are 3.1 eV, 3.5 eV, 3.8 eV, and 4.2 eV respectively. Ultraviolet light of energy E shines on all metals, creating photoelectrons. Which metal has the largest stopping potential

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The stopping potential is the minimum voltage required to stop the emission of photoelectrons from a metal surface when illuminated by light of energy E. It depends on the work function of the metal, which is the minimum energy needed to remove an electron from the surface.

Among the four metals M1, M2, M3, and M4, their work functions are 3.1 eV, 3.5 eV, 3.8 eV, and 4.2 eV respectively. The largest stopping potential will correspond to the metal that has the greatest difference between the energy of the ultraviolet light (E) and its work function. This is because a larger energy difference implies that more energy is required to counteract the emission of photoelectrons.

Assuming the energy E of the ultraviolet light is constant for all metals, the metal with the lowest work function will have the largest energy difference. In this case, M1 has the lowest work function (3.1 eV) and therefore, will have the largest stopping potential among the four metals.

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A 1.0 L buffer solution is 0.250 M HC2H3O2 and 0.050M NAC2H3O2 .Which of the following actions will destroy the buffer effectiveness?

A. adding 0.050 moles of NaC2H3O2

B. adding 0.050 moles of NaOH

C. adding 0.050 moles of HCl

D. adding 0.050 moles of HC2H3O2

E. none of the above

Answers

The correct answer is B. Adding 0.050 moles of NaOH will destroy the buffer effectiveness in buffer solution.


A buffer solution is a solution that can resist changes in pH when small amounts of acid or base are added to it. In this case, the buffer solution consists of acetic acid (HC2H3O2) and its conjugate base (C2H3O2- or NAC2H3O2).

To determine if an action will destroy the buffer effectiveness, we need to consider what happens to the buffer components and how they affect the pH of the solution.

A. Adding 0.050 moles of NaC2H3O2: This will not destroy the buffer effectiveness because we are adding more of the conjugate base, which can react with any added acid to maintain the pH.

B. Adding 0.050 moles of NaOH: This will destroy the buffer effectiveness because the added base will react with the weak acid (HC2H3O2) to form water and the acetate ion (C2H3O2-), which is a strong conjugate base. This will shift the equilibrium towards the products and decrease the concentration of the weak acid, making it less effective at resisting changes in pH.

C. Adding 0.050 moles of HCl: This will not destroy the buffer effectiveness because we are adding acid, which can be neutralized by the buffer components.

D. Adding 0.050 moles of HC2H3O2: This will not destroy the buffer effectiveness because we are adding more of the weak acid, which can react with any added base to maintain the pH.

E. None of the above: This is not the correct answer because option B (adding 0.050 moles of NaOH) will destroy the buffer effectiveness.

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Please answer the following: ("All of the answers are correct" is not the correct answer)

2,3-bisphosphoglycerate:

A. Binds in the central cavity in the T-form of hemoglobin.

B. preferentially binds to oxyhemoglobin and stabilizes it.

C. All of the answers are correct.

D. binds to positively charged groups on the β subunits.

E. binds in the central cavity in the T-form of hemoglobin and binds to positively charged groups on the β subunits.

Answers

2,3-bisphosphoglycerate (2,3-BPG) is a small molecule that binds to haemoglobin in red blood cells. Specifically, it binds to the T-form of haemoglobin, which is a conformational state that has a lower affinity for oxygen than the R-form.

The T-form is stabilized by interactions between the β subunits of haemoglobin.

2,3-BPG binds to positively charged groups on the β subunits of haemoglobin. These interactions occur in the central cavity of the T-form of haemoglobin. The binding of 2,3-BPG to haemoglobin reduces the affinity of haemoglobin for oxygen, which is important in delivering oxygen to tissues. In summary, 2,3-BPG binds to the T-form of haemoglobin in the central cavity and interacts with positively charged groups on the β subunits. This binding reduces the affinity of haemoglobin for oxygen, which is critical for oxygen delivery to tissues.

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