What is the rate constant of a first-order reaction when 20.0% of a reactant remains after 73.5 s?

Answer:

nanograms

Explanation:

Nuclear binding energy refers to the energy needed in order to break up the nucleus of an atom into its component parts: protons and neutrons, it is also the energy used up in the formation of the atom.

The difference between the calculated and actual mass of a nucleus gives its mass defect which is used to calculate the binding energy according to Einstein's equation. The mass differences are usually very small, as little as the order of nanograms.

Answer:

C

Explanation:

Atomic radius generally increases as we move down a group and from left to right across a period

Answer:

Ca²⁺ + 2H⁻ + 2(2H⁺ + O²⁻) ----> Ca²⁺ + 2O²⁻ + 2H⁺ + 4H⁰

              (2 electrons lost)    ---->      (2 electrons gained)

Explanation:

The equation of the reaction is as follows: CaH₂ + 2H₂0 —> Ca(OH)₂ + 2H₂

The oxidation numbers of each of the atoms in the molecules are as follows:

In CaH₂, calcium has an oxidation number of +2, while hydrogen has an oxidation number of -1  ; Ca²⁺, 2H⁻

In 2H₂0, hydrogen has an oxidation number of +1 while oxygen has an oxidation number of -2 ; H⁺, O²⁻

In Ca(OH)₂, calcium has an oxidation number of +2 while oxygen has an oxidation number of -2 and hydrogen has an oxidation number of +1 ; Ca²⁺, O²⁻,  2H⁺

In 2H₂, each hydrogen atom has an oxidation number of 0 ; 4 H⁰

Ca²⁺ + 2H⁻ + 2(2H⁺ + O²⁻) ----> Ca²⁺ + 2O²⁻ + 2H⁺ + 4H⁰

On the left hand side, the hydride ion gives up two electrons to become neutral hydrogen atoms.

On the right hand, two hydrogen atoms accept two electrons to form neutral atoms.

These neutral hydrogen atoms pair up to form two hydrogen gas molecules.

Answer:

96.2 atm

Explanation:

Step 1: Write the balanced equation

2 Na(s) + 2 H₂O(l) → 2 NaOH(aq) + H₂(g)

Step 2: Calculate the moles corresponding to 3.34 kg of sodium

The molar mass of Na is 22.99 g/mol.

[tex]3.34 \times 10^{3} g \times \frac{1mol}{22.99g} =145mol[/tex]

Step 3: Calculate the moles of hydrogen formed from 145 moles of sodium

The molar ratio of Na to H₂ is 2:1. The moles of H₂ formed are 1/2 × 145 mol = 72.5 mol

Step 4: Convert the temperature to the Kelvin scale

K = °C + 273.15 = 50.0°C + 273.15 = 323.2 K

Step 5: Calculate the pressure exerted by the hydrogen gas

We will use the ideal gas equation.

[tex]P \times V = n \times R \times T\\P = \frac{n \times R \times T}{V} = \frac{72.5mol \times 0.0821atm.L/mol.K \times 323.2K}{20.0L} = 96.2 atm[/tex]

Answer:

The answer is: carbon

Explanation:

Organic molecules contain the chemical element carbon (C) in its structure. In this type of molecules, carbon is usually bonded to hydrogen (H), oxygen (O) and, with less frecuency, nitrogen (N). Therefore, in these molecules, carbon forms simple, double and triple bonds with itself. Examples of organic molecules that are very important in biology are carbohydrates, lipids, proteins and nucleic acids.

Answer:

c. 298 K

Explanation:

Nernst equation is an equation used in electrochemistry that relates the reduction potential of a reaction with the standard potential, temperature and concentrations of the reactants in that are been reducted and oxidized. The formula is:

E = E° - RT / nF ln [Red] / [Ox]

Where R is gas constant (8.314J/molK), T is absolute temperature (In Kelvin), n are moles of electrons and F is faraday constant (K/Volt*mol)

In electrochemistry, standard temperature is taken as 298K. That means by assuming standard temperature we can substitute T as:

Explanation:

ΔS denotes change in entropy. Entropy is the degree of disorderliness of a system. An increasing ΔS would mean that the entropy of the products is greater than the entropy of the reactants.

Generally the trend of entropy with state of matter is given as;

Gas > Liquid > Solid (Increasing Entropy)

a. H 2O(g) → H 2O(l)

In this reaction, there is a decreasing ΔS, since we are moving from gas to liquid. This would be the last.

b. 2NO(g) → N 2(g) + O 2(g)

There is an increase in gaseous products. This is definitely an increasing ΔS reaction. This would be the first on the list.

C. MgCO 3(s) → MgO(s) + CO2(g)

The products formed are in solid and gaseous state. There is increasing ΔS but not up to reaction 2.

The order is given as;

b. 2NO(g) → N 2(g) + O 2(g)

C. MgCO 3(s) → MgO(s) + CO2(g)

a. H 2O(g) → H 2O(l)

Answer:

2.15

Explanation:

For this question, we have to remember the pH formula:

[tex]pH~=~-Log[H_3O^+][/tex]

By definition, the pH value is calculated when we do the -Log of the concentration of the hydronium ions ([tex]H_3O^+[/tex]). So, the next step is the calculation of the concentration of the hydronium ions. For this, we have to use the molarity formula:

[tex]M=\frac{mol}{L}[/tex]

We already know the number of moles (0.0231 moles) and the volume (3.33 L). So, we can plug the values into the molarity formula:

[tex]M=\frac{0.0231~moles}{3.33~L}=0.00693~M[/tex]

With this value, now we can calculate the pH value:

[tex]pH~=~-Log[0.00693~M]~=~2.15[/tex]

The pH would be 2.15

I hope it helps!

The experimental design includes the controlled, independent, and dependent variables. The number of crickets and kinds of containers is two constant. Thus, options A and C are correct.

Control variables are the experimental element that remains fixed and unchanged in an experimental setup. They are constant and not are directly related to the interest of the investigation topic but are known to influence the results and observations.

The control variables can influence the dependent variable of the experiment as the number of crickets in each container and the type of container can indirectly alter the outcome and the conclusion of the experiment. The number of cricket will influence the effect of the temperature and the type of container can alter the survival rate.

Therefore, in options A and C. the number of cricket and container are two constants.

Learn more about variables, here:

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Answer:

1.9 × 10⁻²⁶

Explanation:

Step 1: Write the solution reaction for M₂X₃

M₂X₃(s) ⇄ 2 M³⁺(aq) + 3 X²⁻(aq)

Step 2: Make an ICE chart

We can relate the molar solubility (S) with the solubility product constant (Ksp) using an ICE chart.

        M₂X₃(s) ⇄ 2 M³⁺(aq) + 3 X²⁻(aq)

I                              0               0

C                          +2S             +3S

E                            2S               3S

The solubility product constant is:

Ksp = [M³⁺]² × [X²⁻]³ = (2S)² × (3S)³ = 108 S⁵ = 108 (2.8 × 10⁻⁶)⁵ = 1.9 × 10⁻²⁶

The value of Ksp when there is the slightly soluble ionic compound so it should be 1.9 × 10⁻²⁶.

Since the solution reaction for M₂X₃ should be

M₂X₃(s) ⇄ 2 M³⁺(aq) + 3 X²⁻(aq)

Now make an ICE chart

So it can be like

       M₂X₃(s) ⇄ 2 M³⁺(aq) + 3 X²⁻(aq)

I                              0               0

C                          +2S             +3S

E                            2S               3S

Now The solubility product constant is:

Ksp = [M³⁺]² × [X²⁻]³

= (2S)² × (3S)³ = 108 S⁵

= 108 (2.8 × 10⁻⁶)⁵

= 1.9 × 10⁻²⁶

hence, The value of Ksp when there is the slightly soluble ionic compound so it should be 1.9 × 10⁻²⁶.

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Answer:

The change in temperature is [tex]26.06^{\circ} C[/tex].

Explanation:

It is given that,

The specific heat of Aluminium is cal/g°C

Mass of the sample, m = 4.55 g

Heat absorbed, Q = 2.55 cal

We need to find the change in temperature of the sample. The heat absorbed by an object is given by :

[tex]Q=mc\Delta T[/tex]

[tex]\Delta T[/tex] is the change in temperature

So,

[tex]\Delta T=\dfrac{Q}{mc}\\\\\Delta T=\dfrac{2.55\ cal}{4.55\ g\times 0.0215 \ cal/g^{\circ} C}\\\\\Delta T=26.06^{\circ} C[/tex]

So, the change in temperature is [tex]26.06^{\circ} C[/tex].

Answer:

The mass of ascorbic acid in the sample is 0.1076g

Explanation:

In other words to determine ascorbic acid in a sample:

You are adding an amount of I₂. One part is reacting with ascorbic acid and the other with sodium thiosulphate. First, we need to calculate how much thiosulphate reacts to know the iodine that reacts with thiosulphate.

I₂ that reacts with S₂O₃²⁻:

Moles S₂O₃⁻: 0.02030L × (0.196mol / L) = 3.979x10⁻³ moles S₂O₃²⁻.

As 2 moles of S₂O₃²⁻ reacts per moles of I₂, moles of I₂ are:

3.979x10⁻³ moles S₂O₃²⁻ ₓ (1 mole I₂ / 2 moles S₂O₃²⁻) = 1.989x10⁻³ moles I₂

Now, initial amount of I₂ added to the sample is:

0.0500L ₓ (0.0520mol I₂ / L) = 2.600x10⁻³ moles I₂

That means moles of I₂ that react with ascorbic acid = Moles of ascorbic acid are:

2.600x10⁻³ moles I₂ - 1.989x10⁻³ moles I₂ =

6.11x10⁻⁴ moles I₂ = Moles C₆H₈O₆.

To convert moles of substance to mass we need to use molar mass of the substance (176.12g/mol for ascorbic acid):

6.11x10⁻⁴ moles C₆H₈O₆ ₓ (176.12g / mol) =

Answer:

Explanation:

The objective here is to draw the Lewis structure for the polyatomic trisulfide anion and to be sure all resonance structures that satisfy the octet rule are included.

The Lewis structure for  Polyatomic trisulfide anion

The first step is to the layout the skeleton of the Polyatomic trisulfide anion

         S           S           S

However, the next step is to make sure we fill in the bonding pairs of electrons on the central atom.

Then , we move over to filling the lone pairs electrons before we finally have the Lewis structure for  Polyatomic trisulfide anion as shown in the image below.

Answer: [tex]OH^-(aq)+NH_4^+(aq)\rightarrow NH_3(g)+H_2O(l)[/tex]

Explanation:

A double displacement reaction is one in which exchange of ions take place. The salts which are soluble in water are designated by symbol (aq) and those which are insoluble in water and remain in solid form are represented by (s) after their chemical formulas.

[tex]KOH(aq)+NH_4NO_3(aq)\rightarrow KNO_3(aq)+NH_3(g)+H_2O(l)[/tex]

The equation can be written in terms of ions as:

[tex]K^+(aq)+OH^-(aq)+NH_4^+(aq)+NO_3^-(aq)\rightarrow K^+(aq)+NO_3^-(aq)+NH_3(g)+H_2O(l)[/tex]

Spectator ions are defined as the ions which does not get involved in a chemical equation or they are ions which are found on both the sides of the chemical reaction present in ionic form.

The ions which are present on both the sides of the equation are potassium and nitrate ions and hence are not involved in net ionic equation.

Hence, the net ionic equation is :

[tex]OH^-(aq)+NH_4^+(aq)\rightarrow NH_3(g)+H_2O(l)[/tex]

Answer:

FLUORINE, CHLORINE, BROMINE, IODINE, ASTATILE AND TENNESINE

Explanation :

Florine and chorine=gas

Bromine=liquid

ASTATILE and TENNESINE =solid

HOPE IT is right

Answer:

PO4^3-, HPO4^2-

Explanation:

If an acid gives out a proton, the acid then changes to its corresponding base. Similarly, if a base takes in a proton, it changes to its corresponding acid. If a pair of acid and base differ only by the presence or absence of a proton, then they are referred to as a conjugate acid-base pair.

Let us look at this;

HPO4^2-(aq) ----> H^+(aq) + PO4^3-(aq)

HPO4^2- and PO4^3- differ only in the presence or absence of a proton (H^+) hence they constitute a conjugate acid-base pair.

Answer:

Alloys

I hope this helps!

Answer:

D.An alloy

Explanation:

Answer:

0.16 moles of Carbon

Explanation:

The balanced reaction equation:

[tex]2Fe_{2}O_{3}[/tex] + [tex]3C[/tex] → [tex]4Fe[/tex] + [tex]3CO_{2}[/tex]↑

The mole ratio of Carbon to Iron is 3 : 4 (since Fe2O3 is in excess)

i.e 3 moles of C produces 4 moles of Fe.

If 1 mole of Fe - 55.8g of Fe

? moles - 11.6g of Fe

= [tex]\frac{11.6}{55.8}[/tex] = 0.208 moles

But 3 moles of C - 4 moles of Fe

? moles of C - 0.208 moles of Fe

= [tex]\frac{3 *0.208}{4}[/tex] = 0.16 moles of carbon.

I hope this explanation was clear and useful.

Answer:

Vaporization

Explanation:

Vaporization is the change of a specie to the gaseous state. To 'disappear' in this case simply means to change to the gaseous state.

Substances with high vapour pressure tend to be easily converted to vapour phase. Hence if Glade air freshener gel 'disappears' easily, then it has a high vapour pressure and is easily converted to vapour (gas).

Answer:

C. bucky barnes

Explanation:

i dont know how this relates to chemistry

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Explanation:

First convert propane to chloropropane by halogenation reaction in presence of sunlight

CH3-CH2-CH3 + Cl2 → CH3-CH2-CH2Cl + HCl

Chloropropane can be converted into propene by using alcoholic KOH

CH3-CH2-CH2Cl + alc. KOH → CH3-CH=CH2

To convert from Propene to Propan-2-ol, the addition of H2SO4 takes place in accordance with Markovnikov ‘s rule i.e.

Answer:

You'll be left with 0.25 g of phosphorus-32. The nuclear half-life of a radioactive isotope expresses the time needed for a sample of that isotope to reach half of its initial value. In your case, regardless with how much phosphorus-32 you start with, you'll be left with half of that initial mass after 14.0 days.

Explanation:

Answer:

The reactants should be ethyl bromide and sodium methoxide.

The products of the reactions are diethylether and sodium bromide.  

Explanation:

When ethyl bromide, it reacts with any sodium ethoxide, it gives diethylether and also sodium bromide.

As in the sodium ethoxide, the negatively charged oxygen atom is  very much reactive and it  attacks on the bromine containing a carbon of the ethyl bromide and it replaces it forming methyl ethoxide. This type of reaction is sometimes known as SN2.      

Answer:

the answer is (2.54cm in an inch, and 4 number of choices in this question)

Explanation:

An exact number is not rounded, and cannot be changed such as placing a different item on the scale it would change.

Answer:

Bromine.

Explanation:

There is more nuclear charge on bromine because in bromine, there are 35 number of protons and 46 number of neutrons while in selenium, there are 34 number of protons and 45 number of neutrons. The atomic size of selenium is larger because they have lower nuclear charge as compared to bromine and we know that when we go to the left of periodic table atomic size increases which attract the electrons towards itself so the shell comes close to the nucleus and decrease occurs in atomic radius.

Your question has been heard loud and clear.

Specific applications of mass spectrometry include drug testing and discovery, food contamination detection, pesticide residue analysis, isotope ratio determination, protein identification, and carbon dating.

Thank you

The primary function of mass spectrometry is as a tool for chemical analyses based on detection and quantification of ions according to their mass-to-charge ratio. However, mass spectrometry also shows promise for material synthesis.

tbh google

✌️

Answer:

e. 4.1 x 10^−4

Explanation:

For the reaction;

2N2O5(g) → 4NO2(g) + O2(g)

The rate of formation is given as;

(1 / 4) Δ [O2] / Δt = (1 / 2 )Δ [N2O5] / Δt

Δ [O2] / Δt = 8.1 x 10^−4 M/s

Inserting into he equation, we have;

(1/4) (8.1 x 10^−4 ) = (1/2) (Δ [N2O5] / Δt)

2.025 x 10^−4 = (1/2) (Δ [N2O5] / Δt)

Δ [N2O5] / Δt = 2 * 2.025 x 10^−4

Δ [N2O5] / Δt  =  4.1 x 10^−4

Correct option is option E.

Answer: Approximately 69.5 grams of gold (Au).

Explanation:

mol = mass / molar mass

We are already given the moles of gold, 0.353. Looking at a periodic table, we cna bserve that the approximate molar mass of gold is 196.97 (I got this from ptable.com).

Plugging this into the formula above, it will look like this:

0.353 mol Au = mass / (196.97 g/mol)       (in any science class, do not forget about writing your units)

To get mass by itself, multiply both sides of the equation by 196.97 g/mol.

This yields that the mass is equal to 69.5 grams. As you can see, the units of "mol" cancel out: 0.353 mol AU * (196.97 g/mol)

The reason why I rounded my answer to 69.5 grams instead of, let's say, 69.5304, is because of a concept in science referred to as significant figures. In this case, the amount of significant figures we need to round our answer to is seen in the provided value in the problem. 0.353 has only three significant figures so I have rounded the final answer to three significant figures.

Remember, do not forget to not only unclude e units that answer should be in but some teachers also request that you write the symbol of the elemnt you are writing about, so I would write my answer as: 69.5 g Au.

I hope this helps :) have a nice day!

Answer:

Short wavelength UV radiation ----Oxygen (O2 ), nitrogen (N2) , methane (CH4) , water (H2O)  and carbondioxide (CO2).

longer wavelength radiation---- methane (CH4) , water (H2O)  and carbondioxide (CO2)

Explanation:

Oxygen (O2 ), nitrogen (N2) , methane (CH4) , water (H2O)  and carbondioxide (CO2) are the gases which are transparent for incoming short-wavelength UV radiation while  methane (CH4) , water (H2O)  and carbondioxide (CO2) are the greenhouse gases which absorb longer wavelength. When the solar radiation comes to the earth, it has short wavelength but after reflection it converts into longer wavelength which can be prevent by greenhouse gases and increases the temperature of atmosphere.

CH4, H2O and CO2 gases absorb longer wavelength terrestrial re-radiation.

UV radiation are short wavelength radiation that reach the earth from outer space. However, certain gases that compose the atmosphere are able to absorb longer wavelength terrestrial re-radiation.

The following gases absorb longer wavelength terrestrial re-radiation;

The following gases are transparent to  incoming short-wavelength UV radiation;

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Answer:

N2O(g) + 3 H2O(l) ---------------> 2 NH3(g) + 2 O2(g)

Explanation:

If we look at the reaction stated in the question, we will notice that the option chosen in the answer is the reverse of that reaction.

One thing is clear, if a reaction is possible, then its reverse reaction is equally possible. The equilibrium position may shift towards the forward or reverse reaction based on the conditions of the reaction.

Hence if the reaction, 2NH3(g) + 2O2(g) → N2O(g) + 3H2O(l) is possible, then the reaction, N2O(g) + 3 H2O(l) ---------------> 2 NH3(g) + 2 O2(g) is also possible.