Question 1

For the hypothetical second order reaction: A → products,the general rate law is: rate = k[A]².How long is the third half-life of the reaction if [A]₀ is 0.080 M and the first half-life is 22 minutes?

Accepted Answer

We know that the half-life of a second-order reaction is given by:

t1/2 = 1 / k[A]0

where [A]0 is the initial concentration of A.

We can use this formula to find the value of k:

t1/2 = 22 min
[A]0 = 0.080 M

k = 1 / (t1/2 [A]0) = 1 / (22 min * 0.080 M) = 0.568 min^-1 M^-1

Now we can use the integrated rate law for a second-order reaction:

1 / [A]t = kt + 1 / [A]0

We are given that [A]t = 0.080 M / 2^3 = 0.010 M (since we are looking for the third half-life)

Plugging in the values, we get:

1 / 0.010 M = (0.568 min^-1 M^-1) t + 1 / 0.080 M

Solving for t, we get:

t = 88 min

Therefore, the answer is D: 88 min.

Question 2

Nitrogen dioxide decomposes at 300°C via a second-order process to produce nitrogen monoxide and oxygen according to the following chemical equation. 2 NO₂(g)→ 2 NO(g)+ O₂(g). A sample of NO₂(g)is initially placed in a 2.50-L reaction vessel at 300°C.If the half-life and the rate constant at 300°C are 11 seconds and 0.54 M^-1 s^-1,respectively,how many moles of NO₂ were in the original sample?

Accepted Answer

First, we need to use the half-life to find the rate constant (k). The second-order rate law can be written as:

1/[N2O4] = kt + 1/[N2O4]0

where [N2O4]0 is the initial concentration of N2O4 and [N2O4] is the concentration at time t. We know that the half-life is 11 seconds, so we can write:

1/2[N2O4]0 = k(11 s) + 1/[N2O4]0

Simplifying this equation, we get:

k = ln(2) / (2 × 11 s) = 0.0316 s-1

Now we can use the rate constant to find the number of moles of N2O4 in the original sample. The rate law for the decomposition of N2O4 is:

rate = k[N2O4]2

We can use the initial rate to find [N2O4]0:

rate = k[N2O4]0 2

0.54 MS-1 = (0.0316 s-1) [N2O4]0 2

[N2O4]0 = 0.42 mol

Therefore, the answer is (B) 0.42 mol.

Question 3

In aqueous solution,hypobromite ion,BrO^-,reacts to produce bromate ion,BrO₃^-,and bromide ion,Br^-,according to the following chemical equation. 3 BrO^-(aq)→ BrO₃^-(aq)+ 2 Br^-(aq) A plot of 1/[BrO^-] vs.time is linear and the slope is equal to 0.056 M^-1s^-1.If the initial concentration of BrO^- is 0.80 M,how long will it take one-half of the BrO^-ion to react?

Accepted Answer

The answer of In aqueous solution,hypobromite ion,BrO^-,reacts to produce bromate...

Question 4

The second-order reaction,2 Mn(CO)₅ → Mn₂(CO)₁₀ has a rate constant equal to 3.0 × 10⁹ M^-1s^-1 at 25°C.If the initial concentration of Mn(CO)₅ is 1.0 × 10^-5 M,how long will it take for 90.% of the reactant to disappear?

Accepted Answer

The answer of The second-order reaction,2 Mn(CO)₅ → Mn₂(CO)₁₀ has...

Question 5

If the units for rate are M s^-1,what are the units for the rate constant,k,for a zeroth-order reaction?

Accepted Answer

For a zeroth-order reaction, the rate is independent of the concentration of reactants, so the rate constant k has the same units as the rate, which is M s^-1.

Question 6

A mechanism for a naturally occurring reaction that destroys ozone is: Step 1: O₃(g)+ HO(g)→ HO₂(g)+ O₂(g) Step 2: HO₂(g)+ O(g)→ HO(g)+ O₂(g) What is the molecularity of the overall reaction?

Accepted Answer

Molecularity refers to the number of molecules participating in an elementary step of a reaction, not the overall reaction.

Question 7

A researcher needs 5.00 mg of ¹²⁸Ba for an experiment.If the half-life of ¹²⁸Ba is 2.43 days,how many milligrams of ¹²⁸BaCl₂ must she order from the manufacturer if it takes 4.50 days to ship the material from the manufacturer to the university? (Assume the molar mass of ¹²⁸Ba is 128 g/mol. )

Accepted Answer

We can use the following equation to calculate the amount of ¹²⁸BaCl₂ that needs to be ordered: Amount needed = Amount initial x (1/2)^(t/t1/2) Where t is the total time required (4.50 days for shipping + 2.43 days half life = 6.93 days), t1/2 is the half-life (2.43 days) and the initial amount is 5.00 mg. Plugging in these values, we get: Amount needed = 5.00 mg x (1/2)^(6.93/2.43) = 18.0 mg Therefore, the researcher should order 18.0 mg of ¹²⁸BaCl₂ from the manufacturer. The answer is option B.

Question 8

The reaction: 2 HI → H₂ + I₂,is second order and the rate constant at 800 K is 9.70 × 10^-2 M^-1 s^-1.How long will it take for 8.00 × 10^-2 mol/L of HI to decrease to one-fourth of its initial concentration?

Accepted Answer

The reaction is second order, so the rate law can be expressed as:
Rate = k [HI]²
We need to use the integrated rate law for a second-order reaction to solve for the time it takes for the concentration of HI to decrease to one-fourth of its initial value. This is given by:
t = 1 / (k [A]₀) * (1 / 4 - 1)
where [A]₀ is the initial concentration of HI. Substituting the given values:
t = 1 / (9.70 × 10⁻¹² s⁻¹ * 8.00 × 10⁻² M) * (1 / 4 - 1) = 387 s
Therefore, the answer is choice C.

Question 9

Hydrogen iodide decomposes at 800 K via a second-order process to produce hydrogen and iodine according to the following chemical equation. 2 HI(g)→ H₂(g)+ I₂(g) At 800 K it takes 142 seconds for the initial concentration of HI to decrease from 6.75 × 10^-2 M to 3.50 × 10^-2 M.What is the rate constant for the reaction at this temperature?

Accepted Answer

The answer of Hydrogen iodide decomposes at 800 K via...

Question 10

A plot of 1/[BrO^-] vs time is linear for the reaction: 3 BrO^-(aq)→ BrO₃^-(aq)+ 2 Br^-(aq) What is the order of the reaction with respect to the hypobromite ion,BrO^-?

Accepted Answer

The answer of A plot of 1/[BrO^-] vs time is...

Question 11

The elementary reaction representing the formation of ozone: 
Is an example of a ________ reaction.

Accepted Answer

The formation of ozone involves the collision of three molecules (two oxygen molecules and an oxygen atom). This means that the reaction is termolecular, as it involves the collision of three particles. Therefore, the correct answer is (C) termolecular.

Question 12

For the zeroth-order reaction: A → products,what will happen to the rate of reaction if the concentration of A is doubled?

Accepted Answer

In a zeroth-order reaction, the rate of reaction is independent of the concentration of the reactant. Therefore, doubling the concentration of A will not change the rate of the reaction.

Question 13

A mechanism for a naturally occurring reaction that destroys ozone is: Step 1: O₃(g)+ HO(g)→ HO₂(g)+ O₂(g) Step 2: HO₂(g)+ O(g)→ HO(g)+ O₂(g) Which species is an intermediate?

Accepted Answer

HO₂ is produced in step 1 and consumed in step 2, making it an intermediate. HO and O are reactants and products, respectively, and O₃ is not involved in the formation or consumption of the intermediate.

Question 14

For the zeroth-order reaction: C → products,-Δ[C]/Δt = k,which of the following graphs would be expected to give a straight line?

Accepted Answer

The zeroth-order reaction is characterized by a constant rate of reaction, independent of the concentration of the reactant. Therefore, the graph of concentration versus time ([C] vs. t) would be expected to give a straight line.

Question 15

Which statement below regarding the half-life of a second-order reaction is true?

Accepted Answer

In a second-order reaction, the half-life is directly proportional to the initial concentration of the reactant. Therefore, as the concentration of the reactant decreases by half with each half-life, the time required for that decrease will increase. Mathematically, the equation for the half-life of a second-order reaction is t1/2 = 1/[k(Ao)], where k is the rate constant and Ao is the initial concentration. This shows that each half-life is twice as long as the preceding one.

Question 16

The slowest step in a reaction mechanism is called the ________ step.

Accepted Answer

The slowest step in a reaction mechanism is also called the rate-determining step because it determines the overall rate of the reaction.

Question 17

The elementary reaction: 2 HI → H₂ + I₂,is an example of a ________ reaction.

Accepted Answer

This is an example of a bimolecular reaction because it involves two molecules (two molecules of HI) reacting to form two products (H₂ and I₂).

Question 18

A three-step mechanism has been suggested for the formation of carbonyl chloride: Step 1: Cl₂ → 2 Cl Step 2: Cl + CO → COCl Step 3: COCl + Cl₂ → COCl₂ + Cl Which species is an intermediate in the mechanism?

Accepted Answer

In step 2, Cl reacts with CO to form COCl, which is then consumed in step 3. Therefore, COCl is an intermediate in the mechanism. Cl and CO are reactants in their respective steps and COCl₂ is a product of step 3.

Question 19

Which statement below regarding the half-life of a zeroth-order reaction is true?

Accepted Answer

For a zeroth-order reaction, the rate of reaction is constant and does not depend on the concentration of the reactants. As the reaction proceeds and the concentration of the reactants decreases, the amount of substance halved by the reaction in a given time period also decreases. This means that each half-life is shorter than the previous one, leading to the correct statement that each half-life is half as long as the preceding half-life.

Question 20

The decomposition of ozone in the stratosphere can occur by the following two-step mechanism: Step 1: Br + O₃ → BrO + O₂ Step 2: BrO + O → Br + O₂ Which species is an intermediate in this mechanism?

Accepted Answer

BrO is formed in the first step, but it is consumed in the second step to regenerate Br, which is a reactant in the first step. Therefore, BrO is an intermediate species in this mechanism.

Quiz 12: Chemical Kinetics

For the hypothetical second order reaction: A → products,the general rate law is: rate = k[A]².How long is the third half-life of the reaction if [A]₀ is 0.080 M and the first half-life is 22 minutes?

The second-order reaction,2 Mn(CO) ₅ → Mn₂(CO) ₁₀ has a rate constant equal to 3.0 × 10⁹ M^-1s^-1 at 25°C.If the initial concentration of Mn(CO) ₅ is 1.0 × 10^-5 M,how long will it take for 90.% of the reactant to disappear?

If the units for rate are M s^-1,what are the units for the rate constant,k,for a zeroth-order reaction?

A mechanism for a naturally occurring reaction that destroys ozone is: Step 1: O₃(g) + HO(g) → HO₂(g) + O₂(g) Step 2: HO₂(g) + O(g) → HO(g) + O₂(g) What is the molecularity of the overall reaction?

The reaction: 2 HI → H₂ + I₂,is second order and the rate constant at 800 K is 9.70 × 10^-2 M^-1 s^-1.How long will it take for 8.00 × 10^-2 mol/L of HI to decrease to one-fourth of its initial concentration?

A plot of 1/[BrO^-] vs time is linear for the reaction: 3 BrO^-(aq) → BrO₃^-(aq) + 2 Br^-(aq) What is the order of the reaction with respect to the hypobromite ion,BrO^-?

The elementary reaction representing the formation of ozone: Is an example of a ________ reaction.

For the zeroth-order reaction: A → products,what will happen to the rate of reaction if the concentration of A is doubled?

A mechanism for a naturally occurring reaction that destroys ozone is: Step 1: O₃(g) + HO(g) → HO₂(g) + O₂(g) Step 2: HO₂(g) + O(g) → HO(g) + O₂(g) Which species is an intermediate?

For the zeroth-order reaction: C → products,-Δ[C]/Δt = k,which of the following graphs would be expected to give a straight line?

Which statement below regarding the half-life of a second-order reaction is true?

The slowest step in a reaction mechanism is called the ________ step.

The elementary reaction: 2 HI → H₂ + I₂,is an example of a ________ reaction.

A three-step mechanism has been suggested for the formation of carbonyl chloride: Step 1: Cl₂ → 2 Cl Step 2: Cl + CO → COCl Step 3: COCl + Cl₂ → COCl₂ + Cl Which species is an intermediate in the mechanism?

Which statement below regarding the half-life of a zeroth-order reaction is true?

The decomposition of ozone in the stratosphere can occur by the following two-step mechanism: Step 1: Br + O₃ → BrO + O₂ Step 2: BrO + O → Br + O₂ Which species is an intermediate in this mechanism?

Quiz 12: Chemical Kinetics

For the hypothetical second order reaction: A → products,the general rate law is: rate = k[A]2.How long is the third half-life of the reaction if [A]0 is 0.080 M and the first half-life is 22 minutes?

The second-order reaction,2 Mn(CO) 5 → Mn2(CO) 10 has a rate constant equal to 3.0 × 109 M-1s-1 at 25°C.If the initial concentration of Mn(CO) 5 is 1.0 × 10-5 M,how long will it take for 90.% of the reactant to disappear?

If the units for rate are M s-1,what are the units for the rate constant,k,for a zeroth-order reaction?

A mechanism for a naturally occurring reaction that destroys ozone is: Step 1: O3(g) + HO(g) → HO2(g) + O2(g) Step 2: HO2(g) + O(g) → HO(g) + O2(g) What is the molecularity of the overall reaction?

A researcher needs 5.00 mg of 128Ba for an experiment.If the half-life of 128Ba is 2.43 days,how many milligrams of 128BaCl2 must she order from the manufacturer if it takes 4.50 days to ship the material from the manufacturer to the university? (Assume the molar mass of 128Ba is 128 g/mol. )

The reaction: 2 HI → H2 + I2,is second order and the rate constant at 800 K is 9.70 × 10-2 M-1 s-1.How long will it take for 8.00 × 10-2 mol/L of HI to decrease to one-fourth of its initial concentration?

A plot of 1/[BrO-] vs time is linear for the reaction: 3 BrO-(aq) → BrO3-(aq) + 2 Br-(aq) What is the order of the reaction with respect to the hypobromite ion,BrO-?

The elementary reaction representing the formation of ozone: Is an example of a ________ reaction.

For the zeroth-order reaction: A → products,what will happen to the rate of reaction if the concentration of A is doubled?

A mechanism for a naturally occurring reaction that destroys ozone is: Step 1: O3(g) + HO(g) → HO2(g) + O2(g) Step 2: HO2(g) + O(g) → HO(g) + O2(g) Which species is an intermediate?

For the zeroth-order reaction: C → products,-Δ[C]/Δt = k,which of the following graphs would be expected to give a straight line?

Which statement below regarding the half-life of a second-order reaction is true?

The slowest step in a reaction mechanism is called the ________ step.

The elementary reaction: 2 HI → H2 + I2,is an example of a ________ reaction.

A three-step mechanism has been suggested for the formation of carbonyl chloride: Step 1: Cl2 → 2 Cl Step 2: Cl + CO → COCl Step 3: COCl + Cl2 → COCl2 + Cl Which species is an intermediate in the mechanism?

Which statement below regarding the half-life of a zeroth-order reaction is true?

The decomposition of ozone in the stratosphere can occur by the following two-step mechanism: Step 1: Br + O3 → BrO + O2 Step 2: BrO + O → Br + O2 Which species is an intermediate in this mechanism?

For the hypothetical second order reaction: A → products,the general rate law is: rate = k[A]².How long is the third half-life of the reaction if [A]₀ is 0.080 M and the first half-life is 22 minutes?

The second-order reaction,2 Mn(CO) ₅ → Mn₂(CO) ₁₀ has a rate constant equal to 3.0 × 10⁹ M^-1s^-1 at 25°C.If the initial concentration of Mn(CO) ₅ is 1.0 × 10^-5 M,how long will it take for 90.% of the reactant to disappear?

If the units for rate are M s^-1,what are the units for the rate constant,k,for a zeroth-order reaction?

A mechanism for a naturally occurring reaction that destroys ozone is: Step 1: O₃(g) + HO(g) → HO₂(g) + O₂(g) Step 2: HO₂(g) + O(g) → HO(g) + O₂(g) What is the molecularity of the overall reaction?

The reaction: 2 HI → H₂ + I₂,is second order and the rate constant at 800 K is 9.70 × 10^-2 M^-1 s^-1.How long will it take for 8.00 × 10^-2 mol/L of HI to decrease to one-fourth of its initial concentration?

A plot of 1/[BrO^-] vs time is linear for the reaction: 3 BrO^-(aq) → BrO₃^-(aq) + 2 Br^-(aq) What is the order of the reaction with respect to the hypobromite ion,BrO^-?

A mechanism for a naturally occurring reaction that destroys ozone is: Step 1: O₃(g) + HO(g) → HO₂(g) + O₂(g) Step 2: HO₂(g) + O(g) → HO(g) + O₂(g) Which species is an intermediate?

The elementary reaction: 2 HI → H₂ + I₂,is an example of a ________ reaction.

A three-step mechanism has been suggested for the formation of carbonyl chloride: Step 1: Cl₂ → 2 Cl Step 2: Cl + CO → COCl Step 3: COCl + Cl₂ → COCl₂ + Cl Which species is an intermediate in the mechanism?

The decomposition of ozone in the stratosphere can occur by the following two-step mechanism: Step 1: Br + O₃ → BrO + O₂ Step 2: BrO + O → Br + O₂ Which species is an intermediate in this mechanism?