Answer:
5.37 × 10⁻⁴ mol/L
Explanation:
A chemist makes 660. mL of magnesium fluoride working solution by adding distilled water to 230. mL of a 0.00154 mol/L stock solution of magnesium fluoride in water. Calculate the concentration of the chemist's working solution. Round your answer to 3 significant digits.
Step 1: Given data
Initial concentration (C₁): 0.00154 mol/LInitial volume (V₁): 230. mLFinal concentration (C₂): ?Final volume (V₂): 660. mLStep 2: Calculate the concentration of the final solution
We want to prepare a dilute solution from a concentrated one. We can calculate the concentration of the final solution using the dilution rule.
C₁ × V₁ = C₂ × V₂
C₂ = C₁ × V₁ / V₂
C₂ = 0.00154 mol/L × 230. mL / 660. mL = 5.37 × 10⁻⁴ mol/L
The normal freezing point of a certain liquid Xis-7.30°C but when l02. g of iron(III) chloride (FeCl3) are dissolved in 650. g of Xthe solution freezes at -9.9°C instead. Use this information to calculate the molal freezing point depression constant Kf of X.
Answer:
2.7 °C.kg/mol
Explanation:
Step 1: Calculate the freezing point depression (ΔT)
The normal freezing point of a certain liquid X is-7.30°C and the solution freezes at -9.9°C instead. The freezing point depression is:
ΔT = -7.30 °C - (-9.9 °C) = 2.6 °C
Step 2: Calculate the molality of the solution (b)
We will use the following expression.
b = mass of solute / molar mass of solute × kilograms of solvent
b = 102. g / (162.2 g/mol) × 0.650 kg = 0.967 mol/kg
Step 3: Calculate the molal freezing point depression constant Kf of X
Freezing point depression is a colligative property. It can be calculated using the following expression.
ΔT = Kf × b
Kf = ΔT / b
Kf = 2.6 °C / (0.967 mol/kg) = 2.7 °C.kg/mol
Chlorine gas can be prepared in the laboratory by the reaction of hydrochloric acid with manganese(IV) oxide.
4HCl(aq)+MnO2(s)⟶MnCl2(aq)+2H2O(l)+Cl2(g)
A sample of 43.1g MnO2 is added to a solution containing 42.9g HCl.
a. What is the limiting agent?
b. What is the theoretical yield of Cl2?
c. If the yield of the reaction is 72.9%, what is the actual yield of chlorine?
Answer:
A. HCl is the limiting reactant.
B. Theoretical yield of Cl₂ is 20.9 g.
C. Actual yield of Cl₂ = 15.2 g.
Explanation:
The balanced equation for the reaction is given below:
4HCl + MnO₂ –> MnCl₂ + 2H₂O + Cl₂
Next, we shall determine the masses of HCl and MnO₂ that reacted and the mass of Cl₂ produced from the balanced equation. This can be obtained as follow:
Molar mass of HCl = 1 + 35.5
= 36.5 g/mol
Mass of HCl from the balanced equation = 4 × 36.5 = 146 g
Molar mass of MnO₂ = 55 + (2×16)
= 55 + 32
= 87 g/mol
Mass of MnO₂ from the balanced equation = 1 × 87 = 87 g
Molar mass of Cl₂ = 2 × 35.5
= 71 g/mol
Mass of Cl₂ from the balanced equation = 1 × 71 = 71 g
SUMMARY:
From the balanced equation above,
146 g of HCl reacted with 87 g of MnO₂ to produce 71 g of Cl₂.
A. Determination of the limiting reactant.
From the balanced equation above,
146 g of HCl reacted with 87 g of MnO₂.
Therefore, 42.9 g of HCl will react with = (42.9 × 87)/146 = 25.6 g of MnO₂.
From the calculation made above, we can see clearly that only 25.6 g out of 43.1 g of MnO₂ given was needed to react completely with 42.9 g of HCl.
Therefore, HCl is the limiting reactant.
B. Determination of theoretical yield of Cl₂.
Here, the limiting reactant will be used.
From the balanced equation above,
146 g of HCl reacted to produce 71 g of Cl₂.
Therefore, 42.9 g of HCl will react to produce = (42.9 × 71)/146 = 20.9 g of Cl₂.
Thus, the theoretical yield of Cl₂ is 20.9 g.
C. Determination of the actual yield of Cl₂.
Theoretical yield of Cl₂ = 20.9 g
Percentage yield of Cl₂ = 72.9%
Actual yield of Cl₂ =?
Percentage yield = Actual yield / Theoretical yield × 100
72.9% = Actual yield / 20.9
Cross multiply
Actual yield = 72.9% × 20.9
Actual yield = 72.9/100 × 20.9
Actual yield = 0.729 × 20.9
Actual yield of Cl₂ = 15.2 g
what does PH scale measure
Explanation:
pH is a measure of how acidic/basic water is. The range goes from 0 - 14, with 7 being neutral. pHs of less than 7 indicate acidity, whereas a pH of greater than 7 indicates a base.
write the formula
fluoride ion
Answer:
F-
Explanation:
Since Fluorine needs one more electron to reach a full octet, it takes in 1 more electron to become an anion. Therefore, with the extra negative charge from the 1 electron, a Fluoride ion has a charge of -1.
Hope this helped!
Answer:
F_
Explanation:
the symbol or formula
is F_
Which is a property of barium (Ba)?
O A. It rarely reacts with other elements.
O B. It is brittle as a solid.
O c. It is very reactive.
O D. It does not conduct electricity.
Plzzzzz helppppp!!!
Answer:
a it rarely reach with other elements
Explain Boyle's pressure-volume relationship in terms of the kinetic-
molecular theory.
.
Answer:
The pressure and the volume are inversely related in Boyle's Law. In Kinetic theory pressure is created by the collision of particles. If the volume is greater the number of collisions and pressure will be less. So volume and pressure are inversely related if the temperature and total kinetic energy is kept constant.
Explanation:
hope to help you
What are the geometrical shape of BeCl2 and CO2?
Answer:Answer: BeCl2 And CO2 Both Molecules Have The Same - OOOOOOO Molecular Geometry (molecular Shape) Number Of Covalent Bonds To The Central Atom Total Number Of Each Type Of Bond (single, Double, Triple) Number Of Electron Pairs Around The Central Atom Electron Region Geometry (3-D Arrangement Of Electron Pair Regions
Explanation:
B. It shifts the equilibrium toward the right, favoring product.
11. What is meant by the term heat of reaction?
A. the difference in temperature between products and reactants
B. the difference in bond energies between products and reactants
C. the difference in heat energies between products and reactants
What other name is a synonym for this term?
A. entropy change
B. potential change
C. enthalpy change
Answer:
11) the difference in heat energies between products and reactants
12) enthalpy change
Explanation:
The heat of reaction is defined as that energy released or absorbed as chemical substances participate in a chemical reaction. It is a term used to denote the change in energy as reactants change into products.
Another name of heat of reaction is enthalpy of reaction. It is a state function since it depends on the initial and final states of the system.
Select the keyword or phrase that will best complete each sentence. law is a gas law that relates pressure and volume and states that for a fixed amount of gas at constant temperature, the pressure and volume of the gas are ____________ related. ____________ law is a gas law that states that for a fixed amount of gas at constant pressure, the volume of the gas is propotional to its Kelvin temperature. ____________ law is a law that states that the total pressure of a gas mixture is equal to the sum of the partial pressure of its component gases. ____________ law is a gas law that states that the volume of a gas is ____________ proportional to the number of moles of present when the pressure and temperature are held constant. ____________ law is a gas law that states for a fixed amount of gas at constant volume, the pressure of the gas is ____________ proportional to its Kelvin temperature. The ____________ law is a gas law that relates pressure, volume, and temperature. The ____________ law is the equation PV
Answer:
Find answers below.
Explanation:
1. Boyle's law is a gas law that relates pressure and volume and states that for a fixed amount of gas at constant temperature, the pressure and volume of the gas are directly related.
Mathematically, Boyle's law is given by;
[tex] PV = K[/tex]
[tex] P_{1}V_{1} = P_{2}V_{2} [/tex]
Where;
P1 and P2 represents the initial and final pressures respectively.
V1 and V2 represents the initial and final volumes respectively.
2. Charles law is a gas law that states that for a fixed amount of gas at constant pressure, the volume of the gas is propotional to its Kelvin temperature.
Mathematically, Charles is given by;
[tex] VT = K[/tex]
[tex] \frac{V_{1}}{T_{1}} = \frac{V_{2}}{T_{2}}[/tex]
Where;
V1 and V2 represents the initial and final volumes respectively.
T1 and T2 represents the initial and final temperatures respectively.
3. Dalton law is a law that states that the total pressure of a gas mixture is equal to the sum of the partial pressure of its component gases.
4. Avogadro's law is a gas law that states that the volume of a gas is directly proportional to the number of moles of present when the pressure and temperature are held constant.
5. Gay Lussac's law is a gas law that states for a fixed amount of gas at constant volume, the pressure of the gas is directly proportional to its Kelvin temperature.
Mathematically, Gay Lussac's law is given by;
[tex] PT = K[/tex]
[tex] \frac{P1}{T1} = \frac{P2}{T2}[/tex]
6. The combined gas law is a gas law that relates pressure, volume, and temperature.
7. The ideal gas law is the equation PV = nRT
Where;
P is the pressure.
V is the volume.
n is the number of moles of substance.
R is the ideal gas constant.
T is the temperature.
(Ch3ch2)2choh oxidize with k2cr2o7?
Identifying Independent and Dependent Variables Read each of the following short descriptions of an experiment and identify the independent anddependent variables in each. It is likely that you have observed a sealed soda can left out in a hot car expands. Based on the notion that gas escapes a liquid at high temperatures, a student chose to investigate the amount of dissolve oxygen in a local pond over a 12-month period. Sulfur dioxide is a commonly used preservative in wine as it prevents oxidation and bacterial growth. A wine producer would like to explore if pH affects the solubility of SO2 in the wine, and therefore decides to measure the SO2 in the wine solution over a range of pH values. The H2SO4 electrolyte concentration impacts the performance of lead-acid batteries, commonly used as car batteries. A researcher wishes to determine the optimal H2SO4 concentration for the best performance of the battery, as measured by the voltage output. Identify the independent and dependent variable for each scenario in the textfield below.
Saved Biliy Normal X2 X + ELEIE BIT Julie TE
1. Independent variable Dependent variable
2. Independent variable Dependent variable
3. Independent variable Dependent variable
Answer:
a) Independent variable - Temperature
Dependent variable - amount of dissolve oxygen over a 12-month period
b) Independent variable - pH
Dependent variable - solubility of SO2 in the wine
c) Independent variable - H2SO4 concentration
Dependent variable - voltage output.
Explanation:
An independent variable is the one whose value remain constant while a dependent variable is one whose values changes and is dependent on the independent variable
a) Independent variable - Temperature
Dependent variable - amount of dissolve oxygen over a 12-month period
b) Independent variable - pH
Dependent variable - solubility of SO2 in the wine
c) Independent variable - H2SO4 concentration
Dependent variable - voltage output.
What does the rate law tell you about a reaction?
A. How the concentration of the reactants affects the rate of a
reaction
B. How temperature affects the rate of a reaction
C. How the equilibrium constant is related to the rate of a reaction
D. How the rate of a reaction affects the total time of a reaction
Answer:
A. How the concentration of the reactants affects the rate of a reaction
Explanation:
Let's consider a generic reaction.
A + B ⇒ Products
The generic rate law is:
rate = k × [A]ᵃ × [B]ᵇ
where,
rate: rate of the reaction[A] and [B]: molar concentrations of the reactantsk: rate constanta and b: reaction ordersAs we can see, the rate law shows how the concentration of the reactants affects the rate of a reaction.
list some applications of chemistry in your dail life
Chemistry and chemical reactions are not just limited to the laboratories but also the world around you.
Chemistry in Food Production:
Plants produce food for themselves through photosynthesis; which is a complex chemical reaction in itself. The chemical reaction that takes place in photosynthesis is the most common and vital chemical reaction.
6 CO2 + 6 H2O + light → C 6H12O6 + 6 O2
Chemistry in Hygiene:
Right before you consume your food, you make it a point to wash your hands with soap. Isn’t it? The cleaning action of soap is based on its ability to act as an emulsifying agent. Soaps are fatty acids salts of sodium or potassium; produced by a chemical reaction called saponification. Soaps interact with the grease or oil molecule, which, in turn, results in a cleaner surface.
The Chemistry of an Onion:
Ever wondered why you shed tears while chopping an onion? This also happens because of the underlying chemistry concepts. As soon as you slice an onion, sulfenic acid is formed from amino acid sulfoxides. Sulfenic acid is responsible for the volatile gas, propanethiol S-oxide, that stimulates the production of tears in the eyes.
Chemistry in Baking:
Who does not like to eat fluffy freshly baked bread? Baking soda is an efficient leavening agent. The addition of baking soda to food items before cooking leads to the production of carbon dioxide (CO2); which causes the foods to rise. This whole process of rising of baked good is called chemical leavening.
Chemistry in Food Preservatives:
In case you ever read the ingredients on the bottle of ketchup, jams or pickles, you might be surprised to see a never-ending list of chemicals. What are they? These chemicals are called food preservatives; which delay the growth of microorganisms in foods. The chemical food preservatives not only prohibit the growth of bacteria, virus, fungi but also hinder the oxidation of fats, which is responsible for making the foods rancid. The most common chemical food preservatives are sodium benzoate, sorbic acid, potassium sorbate, calcium sorbate, sodium sorbate, propionic acid, and the salts of nitrous acid.
Chemistry in Digestion
The moment you put food in your mouth, a number of different chemical reactions start in your digestive tract. Saliva contains the enzyme amylase, which is responsible for breaking down carbohydrates, the stomach starts producing hydrochloric acid, the liver releases bile and the list of compounds released during digestion goes on. How do they work? All these enzymes undergo chemical reactions so that proper digestion, as well as assimilation of the food, occurs.
The Working of a Sunscreen
Before going out on a sunny day, you make it a point to wear sunscreen. Even the principle, behind the working of a sunscreen, has a chemistry background. The sunscreen uses a combination of organic and inorganic compounds to act as a filter for incoming ultraviolet rays. Sunblocks, on the other hand, scatter away UV light; so that it is unable to penetrate deep into the skin. Sunblocks contain complex chemical compounds like zinc oxide or titanium oxide, which prevent the UV rays to invade deeper into the skin.
Chemistry in Rust Formation
With time, your iron instruments start developing an orange-brown flaky coating called rust. The rusting of iron is a type of oxidation reaction. The atoms in the metal iron undergo oxidation and reduction; causing rusting. The formation of verdigris on copper and the tarnishing of silver are also the other everyday examples of chemical reactions. The chemical equation underlying rusting is:
Fe + O2 + H2O → Fe2O3. XH2O
Hope it helps.
3. Calculate the answers to the appropriate number of significant figures. e) 43.678 x 64.1 = f) 1.678/0.42 =
Fabric A is used to rub a wooden rod. A second piece of Fabric A is used to rub an ebonite rod. It is observed that the wooden rod and the ebonite rod attract one another. What can you say about the position of Fabric A in the electrostatic series in relation to wood and ebonite?
Fabric A is likely to be a material that has a moderate tendency to gain electrons when in contact with other materials and is lower in the electrostatic series than ebonite but higher than wood.
What is electrostatic series?The electrostatic series is a list of materials ranked in order of their tendency to gain or lose electrons when in contact with another material.
Materials higher in the series tend to lose electrons more readily and become positively charged, while materials lower in the series tend to gain electrons more readily and become negatively charged.
Ebonite is a synthetic polymer that is known to become negatively charged when rubbed, and it is typically placed near the top of the electrostatic series.
Wood, on the other hand, is a poor conductor of electricity and does not readily become charged when rubbed. Based on these facts, we can infer that Fabric A is lower in the electrostatic series than ebonite, but higher than wood.
To learn more about an electrostatic series, follow the link:
https://brainly.com/question/31065393
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For alkyl halides used in SN1 and SN2 mechanisms, rank the leaving groups in order of reaction rate. You are currently in a ranking module. Turn off browse mode or quick nav, Tab to move, Space or Enter to pick up, Tab to move items between bins, Arrow Keys to change the order of items, Space or Enter to drop.
Answer:
Iodide> Bromide > chloride > flouride
Explanation:
During a nucleophilic substitution reaction, a nucleophilie replaces another in a molecule.
This process may occur via an ionic mechanism (SN1) or via a concerted mechanism (SN2).
In either case, the ease of departure of the leaving group is determined by the nature of the C-X bond. The stronger the C-X bond, the worse the leaving group will be in nucleophilic substitution. The order of strength of C-X bond is F>Cl>Br>I.
Hence, iodine displays the weakest C-X bond strength and it is thus, a very good leaving group in nucleophillic substitution while fluorine displays a very high C-X bond strength hence it is a bad leaving group in nucleophilic substitution.
Therefore, the ease of the use of halide ions as leaving groups follows the trend; Iodide> Bromide > chloride > flouride
Nuclear reactions take place inside the nucleus of the atom. Which of the following does NOT represent an everyday example of a nuclear reaction?
Conversion of carbon dioxide and water in photosynthesis
Hydrogen atoms fused together in the Sun
Loss of protons and electrons in plutonium-240 decay
Energy produced by the Sun that is transferred to Earth
Answer:
Loss of protons and electrons in plutonium 240 decay is not an example of an everyday reaction
The following compounds all show a single line in their 1H NMR spectra. List them as they would appear in an NMR spectrum, e.g. by decreasing chemical shift with the lowest shift to the right. These compounds would appear in a spectrum in the order.
a. Benzene
b. CH4
c. Cyclohexane
These compounds would appear in a spectrum in the order: _
Answer:
Benzene < Cyclohexane < CH4
Explanation:
The location of a peak in an NMR spectrum is determined by chemical shift. In 1H NMR, a proton that is strongly shielded, It implies a proton that has a high electron density, is exposed to a low magnetic field, which causes the chemical shift to diminish, resulting in a signal towards the right direction of the spectrum.
However, a de-shielded proton with its electron density reduced is exposed to a high magnetic field, which causes and resulted in a chemical shift and causes it to shift to the left of the spectrum.
Electronegativity is one of the factors that influence the electron density because it decreases the proton's electron density attached to it as well as the ones attached to nearby atoms due to the inductive effect. The impact of an electronegative atom diminishes fast as the distance between them grows.
We can utilize the impact of electronegativity to calculate how much chemical shift will take place in each molecule in this question.
The chemical shift for benzene is = 7.26 ppm
Chemical shift for cyclohexane is = 1.44 ppm
Chemical shift for methane = 0.23 ppm
Thus, in decreasing order, the chemical shift with the lowest shift from left to right is:
Benzene < Cyclohexane < CH4
A certain first-order reaction is 45.0% complete in 65 s. What are the values of the rate constant and the half-life for this process
Answer:
0.01228s⁻¹ = rate constant
Half-life = 56.4s
Explanation:
The first order reaction follows the equation:
ln[A] = -kt + ln[A]₀
Where [A] is amount of reactant after time t = 45.0%, k is rate constante and [A]₀ initial amount of reactant = 100%
ln[45%] = -k*65s + ln[100%]
-0.7985 = -k*65s
0.01228s⁻¹ = rate constant
Half-life is:
Half-life = ln2 / k
Half-life = 56.4s
Spell out the full name of the compound.
Submit
Help plz
Explanation:
A=Butan-2-one
B=Pentan-3-one
Trộn 100ml dung dịch H2SO4 0,03M với 200ml dung dịch HCl 0,03M và 0,001mol Ba(OH)2 0,05M . Hãy tính pH của dung dịch này?
Answer:
pH = 1.92Explanation:
[H+] = 0.1x0.03x2 + 0.2x0.03 = 0.012 mol
[OH-] = 0.001x0.05x2 = 0.0001 mol
=> [H+] dư = 0.012 - 0.0001 =0.0119 mol
pH = -log[H+] = 1.92
Complete the sentence.
Hexene would have _ carbon atoms and one _ bond
First blank options:
7, 8, 1, 2, 4, 3, 5, 6
Second blank options:
single, double, triple
Answer:
6, double
Explanation:
Hex- is a prefix for number 6.
Ene- is a suffix for a double bond.
Complete a chair conformation of trans-1-bromo-3-methylcyclohexane by placing the hydrogen, bromine, and methyl groups in the appropriate positions.
Place the bromine on the carbon that is more to the right.
Answer:
Explanation:
The most highly stable cycloalkane is cyclohexane. It does not suffer from an angle or torsional strain, and it has the appropriate stability as chain alkanes. Because of the peculiar conformation it takes, this stability leads to the cyclohexane conformation popularly known as the "chair" conformation.
However, from the information given;
The chair conformation structure of trans-1-bromo-3-methylcyclohexane is carefully drawn and the substituents are appropriately attached in the image below.
The literature values listed for the unknowns in this assignment are from either the Merck Index or the CRC Handbook, the two most used reference handbooks. However, the values tend to vary slightly across literature sources and sometimes the temperatures are given as ranges. Give at least one reason for the variations in these reported temperatures.
In general, the boiling points of compounds increase down a group in the periodic table. The melting points and boiling points for the hydrogen compounds of group 6A elements are in the table below.
Melting point (0C) Boiling point (oC)
H2O 0.0 100.0
H2S -82.0 -60.0
H2Se -65.7 -41.2
H2Te -49.0 -2.2
Answer:
See explanation
Explanation:
One of the important trends in the periodic table is electronegativity. Electro negativity decreases down the group and increases across the period. This trend has important consequences on the observed properties of the compounds of elements in a particular group in the periodic table.
As we move down in group 6A, the electro negativity of the elements elements the group decrease and as such, the magnitude of intermolecular hydrogen bonding between the molecules also decrease accordingly. Hydrogen bonds occur between
molecules of a substance when hydrogen is covalently bonded to an electronegative element. Hydrogen bonding is responsible for the high melting and boiling points of small molecules such as water which contain the highly electronegative oxygen atom.
So, as we move down the group there is lesser intermolecular hydrogen bonding between the hydride molecules of group 6A elements resulting in the observed trend in melting and boiling points of the hydrides.
The weaker hydrogen bonds that occurbetween molecules of group 6A hydrides lead to a steady decrease in melting and boiling points of the hydrides of group 6A elements as we move down the group.
A buffer solution contains 0.298 M ammonium chloride and 0.478 M ammonia. If 0.0560 moles of hydroiodic acid are added to 225 mL of this buffer, what is the pH of the resulting solution?
Answer:
pH = 8.87
Explanation:
Hydroiodic acid, HI, is a strong acid that reacts with ammonia, NH3, to produce ammonium ion, NH⁴⁺. That means the moles of HI added = moles of NH3 consumed and moles of NH4⁺ produced.
Initial moles NH₄⁺:
0.225L * (0.298mol/L) = 0.06705 moles
Initial moles NH3:
0.225L * (0.478mol/L) = 0.10755 moles
After the reaction the moles are:
0.10755moles NH3 - 0.0560moles = 0.05155 moles NH3
0.06705moles NH4+ + 0.0560moles = 0.12305 moles NH4+
Using H-H equation for weak bases:
pOH = pKb + log ([NH4+] / [NH3])
pKb for ammonia is 4.75, [NH4+] could be the moles of NH4+ = 0.12305mol,
[NH3] = 0.05155moles
Replacing:
pOH = 4.75 + log (0.12305mol / 0.05155moles)
pOH = 5.13
pH = 14-pOH
pH = 8.87Hydrogen gas can be prepared in the laboratory by a sin- gle-displacement reaction in which solid zinc reacts with hydrochloric acid. How much zinc in grams is required to make 14.5 g of hydrogen gas through this reaction
Answer:
941 g
Explanation:
Step 1: Write the balanced equation
Zn + 2 HCl ⇒ ZnCl₂ + H₂
Step 2: Calculate the moles corresponding to 14.5 g of H₂
The molar mass of H₂ is 1.01 g/mol.
14.5 g × 1 mol/1.01 g = 14.4 mol
Step 3: Calculate the number of moles of Zn required to form 14.4 moles of H₂
The molar ratio of Zn to H₂ is 1:1. The moles of Zn required are 1/1 × 14.4 mol = 14.4 mol.
Step 4: Calculate the mass corresponding to 14.4 moles of Zn
The molar mass of Zn is 65.38 g/mol.
14.4 mol × 65.38 g/mol = 941 g
Astatine is a halogen with several isotopes that all have short half-lives. Which of the following combinations of mass number and neutrons are possible as isotopes of astatine? Choose one or more:
i) A = 211, n = 127
ii) A = 210, n = 125
iii) A = 220, n = 134
iv) A = 207, n = 122
v) A = 209, n = 124
Answer:
Astatine is a halogen with several isotopes that all have short half-lives.
Which of the following combinations of mass number and neutrons are possible as isotopes of astatine? Choose one or more:
i) A = 211, n = 127
ii) A = 210, n = 125
iii) A = 220, n = 134
iv) A = 207, n = 122
v) A = 209, n = 124
Explanation:
The mass number is the sum of the number of protons and the number of neutrons in an atom.[tex]A=no.of protons+no.of neutrons\\=>no.of neutrons=A-no.of protons\\[/tex]
Atomic number of At(astatine ) =85
That means it has --- 85protons.
Its mass number A=210
Hence, the number of neutrons in At are:
[tex]n=A-Z\\=>n=210-85\\=>n=125[/tex]
Second option:
ii) A=210 , n=125 is the answer.
A buffer solution contains 0.472 M hydrocyanic acid and 0.342 M sodium cyanide. If 0.0194 moles of sodium hydroxide are added to 150 mL of this buffer, what is the pH of the resulting solution
Answer:
pH = 9.54.
Explanation:
Hello there!
In this case, since this is an acidic buffer due to the hydrocyanic acid, it will be firstly necessary for us to calculate the moles of both acid and conjugate base in 150 mL given their concentrations:
[tex]n_{acid}=0.472mol/L*0.150L=0.0708mol\\\\n_{base}=0.342mol/L*0.150L=0.0513mol[/tex]
Next, since the effect of adding NaOH, consume the acid and produce more base, we subtract 0.0194 moles from 0.0708 mol and add 0.0194 to 0.0513 mol for us to calculate the new moles:
[tex]n_{acid}^{new}=0.0708mol-0.0194mol=0.0514mol\\\\n_{base}^{new}=0.0513mol+0.0194mol=0.0707mol[/tex]
Thus, since the pKa of hydrocyanic acid is 9.40, we therefore use the Henderson-Hasselbach equation to calculate the pH of the resulting solution for the same volume:
[tex]pH=9.40+log(\frac{0.0707mol}{0.0514mol} )\\\\pH=9.54[/tex]
Which increase make sense since we added some strong base.
Regards!
1.00 liter solution contains 0.31 M acetic acid and 0.40 M sodium acetate. If 0.100 moles of calcium hydroxide are added to this system, indicate whether the following statements are true or false. (Assume that the volume does not change upon the addition of calcium hydroxide.)
_______ A. The number of moles of CH3COOH will decrease.
_______ B. The number of moles of CH3COO- will decrease.
_______ C. The equilibrium concentration of H3O will decrease.
_______ D. The pH will decrease.
_______ E. The ratio of [CH3COOH] / [CH3COO-] will remain the same.
Answer:
The answer is the explanation.
Explanation:
The acetic acid, CH3COOH, reacts with calcium hydroxide, Ca(OH)2, producing acetate ion, CH3COO- and water as follows:
2CH3COOH + Ca(OH)2 → 2CH3COO- + 2H2O + Ca²⁺
That means the moles of acetic acid decrease whereas the moles of acetate ion are increased. The ratio of [CH3COOH] / [CH3COO-] is different.
As a base is added, the concentration of H3O+ decreases increasing the pH.
That means:
TRUE A. The number of moles of CH3COOH will decrease.
FALSE B. The number of moles of CH3COO- will decrease.
TRUE C. The equilibrium concentration of H3O will decrease.
FALSE D. The pH will decrease.
FALSE E. The ratio of [CH3COOH] / [CH3COO-] will remain the same.
The products in a decomposition reaction _____. are compounds can be elements or compounds are elements include an element and a compound
Answer:
compounds are elements include an element and a compound
Explanation:
elements in the decomposition reaction is the substance that cannot be separated into simpler substances. Compounds, technically act as a reactant in the decomposition reaction, but since the reaction breakdown one substance into two or more, sometimes it exists in the product