Question 1

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

Accepted Answer

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

Question 2

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 1.0 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 3

The first-order reaction,SO₂Cl₂ → SO₂ + Cl₂,has a half-life of 8.75 hours at 593 K.How long will it take for the concentration of SO₂Cl₂ to fall to 14.5% of its initial value?

Accepted Answer

For a first-order reaction, the time $t$ required for a reactant to fall to a certain percentage of its initial concentration can be calculated using the formula $t = \frac{\ln(\frac{[A]_0}{[A]})}{k}$, where $[A]_0$ is the initial concentration, $[A]$ is the final concentration, and $k$ is the rate constant. The half-life ($t_{1/2}$) of a first-order reaction is given by $t_{1/2} = \frac{0.693}{k}$. Given that the half-life is 8.75 hours, we can find $k = \frac{0.693}{8.75}$ hours$^{-1}$. To find the time it takes for the concentration to fall to 14.5% of its initial value, we use the initial and final concentration ratio in the formula, where $\frac{[A]}{[A]_0} = 0.145$. Substituting the values and solving for $t$ gives a time significantly longer than the half-life, indicating that option D (24.4 hours) is the correct answer, as it represents a substantial decrease to 14.5% of the initial concentration, which is consistent with the nature of exponential decay in first-order reactions.

Question 4

A gaseous reaction occurs by a two-step mechanism,shown below. Step 1: AX +Y₂ ⇌ AXY_{2 fast} Step 2: AXY₂ + AX → 2 AXY slow Including concentration of only reactants and products,what is the rate law for this reaction?

Accepted Answer

The answer of A gaseous reaction occurs by a two-step...

Question 5

The isomerization reaction,CH₃NC → CH₃CN,is first order and the rate constant is equal to 0.46 s^-1 at 600 K.What is the concentration of CH₃NC after 0.20 minutes if the initial concentration is 0.40 M?

Accepted Answer

Explanation:The integrated rate law for a first-order reaction is:ln[A]t=−kt+ln[A]0where [A]t is the concentration of the reactant at time t, k is the rate constant, and [A]0 is the initial concentration of the reactant.Substituting the given values into the integrated rate law, we get:ln[CH3NC]t=−(0.46s−1)(0.20min)(60smin)+ln(0.40M)ln[CH3NC]t=−5.52+−0.916[CH3NC]t=e−5.52+−0.916=1.6×10−3MTherefore, the concentration of CH3NC after 0.20 minutes is 1.6 × 10−3 M.

Question 6

The first-order reaction,2 N₂O(g)→ 2 N₂(g)+ O₂(g),has a rate constant equal to 0.76 s^-1 at 1000 K.How long will it take for the concentration of N₂O to decrease to 6.0% of its initial concentration?

Accepted Answer

For a first-order reaction, the time to reach a certain concentration can be calculated using the formula: t = (1/k) * ln([A]₀/[A]). Here, k = 0.76 s⁻¹, [A]₀/[A] = 1/0.06. Plugging in the values, t = (1/0.76) * ln(1/0.06) ≈ 3.7 s.

Question 7

For the first-order reaction,2 N₂O(g)→ 2 N₂(g)+ O₂(g),what is the concentration of N₂O after 3 half-lives if mol of N₂O is initially placed into a 1.00-L reaction vessel?

Accepted Answer

The answer of For the first-order reaction,2 N₂O(g)→ 2 N₂(g)+...

Question 8

The following reaction is first order,C₂H₆ → 2 CH₃.If the rate constant is equal to 5.5 × 10^-4 s^-1 at 1000 K,how long will it take for 0.35 mol of C₂H₆ in a 1.00 L container to decrease to 0.25 mol in the same container?

Accepted Answer

For a first-order reaction, the time can be calculated using the formula: t = (1/k) * ln([A]₀/[A]). Substituting the given values: k = 5.5 × 10⁻⁴ s⁻¹, [A]₀ = 0.35 mol/L, [A] = 0.25 mol/L, we find t ≈ 600 seconds, which is 10 minutes.

Question 9

Hydrogen iodide decomposes at 800 K via a second-order process to produce hydrogen and iodine according to the following chemical equation. 2HI(g)→ H₂(g)+ I₂(g) At 800 K it takes 233 seconds for the initial concentration of HI to decrease from 5.75 × 10^-2 M to 2.50 × 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

The reaction A + B C + D occurs in one step.The activation energy is 132 kJ/mol and ΔE = -236 kJ/mol.What is the activation energy for the reverse reaction?

Accepted Answer

The activation energy for the reverse reaction can be calculated using the relationship:

ΔE(reverse) = ΔE(forward)
- Ea(reverse) + Ea(forward)
where
ΔE(forward) = -236 kJ/mol (given)
Ea(forward) = 132 kJ/mol (given)

Substituting the values, we get:

ΔE(reverse) = -236 kJ/mol
- Ea(reverse) + 132 kJ/mol

Solving for Ea(reverse), we get:

Ea(reverse) = 132 kJ/mol - 236 kJ/mol = -104 kJ/mol

Therefore, the answer is B, -104.

Question 11

The aquation of tris(1,10-phenanthroline)iron(II)in acid solution takes place according to the equation: Fe(phen)₃²⁺ + 3 H₃O⁺ + 3 H₂O → Fe(H₂O)₆²⁺ + 3 phenH⁺ If the activation energy,E_a,is 126 kJ/mol and the rate constant at 30°C is 9.8 × 10^-3 min^-1,what is the rate constant at 40°C?

Accepted Answer

We can use the Arrhenius equation:

k2 = k1 * exp((Ea/R) * (1/T1 - 1/T2))

where k1 is the rate constant at temperature T1, k2 is the rate constant at temperature T2, Ea is the activation energy, R is the gas constant (8.314 J/mol·K), and T1 and T2 are the temperatures in kelvin.

Plugging in the given values:

k2 = (9.8 × 10-3 min-1) * exp((126000 J/mol / 8.314 J/mol·K) * (1/303 K - 1/313 K))

k2 = 4.8 × 10-2 min-1

Therefore, the rate constant at 40°C is approximately 4.8 × 10-2 min-1, which corresponds to answer choice B.

Question 12

Which general rate law below corresponds to an elementary bimolecular reaction?

Accepted Answer

In an elementary bimolecular reaction, the rate law is directly proportional to the concentration of the reactants involved. For a bimolecular reaction involving two molecules of the same reactant, the rate law is Rate = k[A]^2.

Question 13

The rate constant,k,for a first-order reaction is equal to 6.2 × 10^-4 s^-1.What is the half-life for the reaction?

Accepted Answer

The half-life for a first-order reaction is calculated using the formula t_1/2 = 0.693/k. Substituting k = 6.2 × 10^-4 s^-1, we get t_1/2 ≈ 1.1 × 10³ s.

Question 14

What fraction of collisions will have sufficient energy to react for a gas whose activation energy is 68 kJ/mol at 25°C?

Accepted Answer

The fraction of collisions with sufficient energy to react is given by the Arrhenius equation: f = e^(-Ea/RT). For Ea = 68 kJ/mol, T = 298 K, and R = 8.314 J/mol·K, f ≈ 1.2 × 10^-12.

Question 15

What is the rate law for the elementary reaction shown below? 2 HI → H₂ + I₂

Accepted Answer

The answer of What is the rate law for the...

Question 16

The second-order reaction 2 Mn(CO)₅ → Mn₂(CO)₁₀,has a rate constant equal to 3.0 × 10⁹ M^-1 s^-1 at 25°C.If the initial concentration of Mn(CO)₅ is 5.0 × 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 17

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 44 seconds and 0.54 M^-1 s^-1,respectively,how many moles of NO₂ were in the original sample?

Accepted Answer

We can use the second-order integrated rate law for a reactant to solve this problem:

1/[NOS]t - 1/[NOS]0 = kt

where [NOS]t is the concentration of NOS at time t, [NOS]0 is the initial concentration of NOS, k is the rate constant, and t is the time.

We are given that the half-life (t1/2) of the reaction is 44 seconds, which means that [NOS]t = 0.5[NOS]0 when t = t1/2. Substituting these values into the integrated rate law, we can solve for [NOS]0:

1/(0.5[NOS]0) - 1/[NOS]0 = k(44 s)
1/[NOS]0 = 2/(k(44 s)) + 1/(0.5[NOS]0)
1/[NOS]0 = 4/(k(44 s)) (since 0.5[NOS]0 cancels out)

Now we just need to plug in the given values for k and solve for [NOS]0:

1/[NOS]0 = 4/(0.54 MS-1)
[NOS]0 = 0.11 mol/L

Finally, we can calculate the total number of moles of NOS in the 2.50-L reaction vessel:

moles of NOS = concentration x volume = 0.11 mol/L x 2.50 L = 0.275 mol

Therefore, the best choice is B) 0.11 mol, which is the initial number of moles of NOS in the sample.

Question 18

A three-step mechanism has been suggested for the formation of COCl₂: 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

COCl is formed in step 2 and consumed in step 3, which makes it an intermediate in the mechanism.

Question 19

The first-order reaction,SO₂Cl₂ → SO₂ + Cl₂,has a rate constant equal to 2.20 × 10^-5 s^-1 at 593 K.What percentage of the initial amount SO₂Cl₂ will remain after 3.00 hours?

Accepted Answer

For a first-order reaction, the percentage remaining can be calculated using the formula: % remaining = 100 * e^(-kt). Substituting k = 2.20 × 10^-5 s^-1 and t = 3 hours (or 10800 seconds), we find that approximately 78.9% of SO2Cl2 remains.

Question 20

The elementary reaction: 2 HF → H₂ + F₂,is an example of a ________ reaction.

Accepted Answer

The given elementary reaction involves the collision of two HF molecules, indicating that this is a bimolecular reaction.

Quiz 13: Chemical Kinetics

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

The first-order reaction,SO₂Cl₂ → SO₂ + Cl₂,has a half-life of 8.75 hours at 593 K.How long will it take for the concentration of SO₂Cl₂ to fall to 14.5% of its initial value?

A gaseous reaction occurs by a two-step mechanism,shown below. Step 1: AX +Y₂ ⇌ AXY_{2 fast} Step 2: AXY₂ + AX → 2 AXY slow Including concentration of only reactants and products,what is the rate law for this reaction?

The isomerization reaction,CH₃NC → CH₃CN,is first order and the rate constant is equal to 0.46 s^-1 at 600 K.What is the concentration of CH₃NC after 0.20 minutes if the initial concentration is 0.40 M?

The first-order reaction,2 N₂O(g) → 2 N₂(g) + O₂(g) ,has a rate constant equal to 0.76 s^-1 at 1000 K.How long will it take for the concentration of N₂O to decrease to 6.0% of its initial concentration?

For the first-order reaction,2 N₂O(g) → 2 N₂(g) + O₂(g) ,what is the concentration of N₂O after 3 half-lives if mol of N₂O is initially placed into a 1.00-L reaction vessel?

The following reaction is first order,C₂H₆ → 2 CH₃.If the rate constant is equal to 5.5 × 10^-4 s^-1 at 1000 K,how long will it take for 0.35 mol of C₂H₆ in a 1.00 L container to decrease to 0.25 mol in the same container?

The reaction A + B C + D occurs in one step.The activation energy is 132 kJ/mol and ΔE = -236 kJ/mol.What is the activation energy for the reverse reaction?

Which general rate law below corresponds to an elementary bimolecular reaction?

The rate constant,k,for a first-order reaction is equal to 6.2 × 10^-4 s^-1.What is the half-life for the reaction?

What fraction of collisions will have sufficient energy to react for a gas whose activation energy is 68 kJ/mol at 25°C?

What is the rate law for the elementary reaction shown below? 2 HI → H₂ + I₂

The second-order reaction 2 Mn(CO) ₅ → Mn₂(CO) ₁₀,has a rate constant equal to 3.0 × 10⁹ M^-1 s^-1 at 25°C.If the initial concentration of Mn(CO) ₅ is 5.0 × 10^-5 M,how long will it take for 90.% of the reactant to disappear?

A three-step mechanism has been suggested for the formation of COCl₂: 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 first-order reaction,SO₂Cl₂ → SO₂ + Cl₂,has a rate constant equal to 2.20 × 10^-5 s^-1 at 593 K.What percentage of the initial amount SO₂Cl₂ will remain after 3.00 hours?

The elementary reaction: 2 HF → H₂ + F₂,is an example of a ________ reaction.

Quiz 13: Chemical Kinetics

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

The first-order reaction,SO2Cl2 → SO2 + Cl2,has a half-life of 8.75 hours at 593 K.How long will it take for the concentration of SO2Cl2 to fall to 14.5% of its initial value?

A gaseous reaction occurs by a two-step mechanism,shown below. Step 1: AX +Y2 ⇌ AXY2 fast Step 2: AXY2 + AX → 2 AXY slow Including concentration of only reactants and products,what is the rate law for this reaction?

The isomerization reaction,CH3NC → CH3CN,is first order and the rate constant is equal to 0.46 s-1 at 600 K.What is the concentration of CH3NC after 0.20 minutes if the initial concentration is 0.40 M?

The first-order reaction,2 N2O(g) → 2 N2(g) + O2(g) ,has a rate constant equal to 0.76 s-1 at 1000 K.How long will it take for the concentration of N2O to decrease to 6.0% of its initial concentration?

For the first-order reaction,2 N2O(g) → 2 N2(g) + O2(g) ,what is the concentration of N2O after 3 half-lives if mol of N2O is initially placed into a 1.00-L reaction vessel?

The following reaction is first order,C2H6 → 2 CH3.If the rate constant is equal to 5.5 × 10-4 s-1 at 1000 K,how long will it take for 0.35 mol of C2H6 in a 1.00 L container to decrease to 0.25 mol in the same container?

The reaction A + B C + D occurs in one step.The activation energy is 132 kJ/mol and ΔE = -236 kJ/mol.What is the activation energy for the reverse reaction?

The aquation of tris(1,10-phenanthroline) iron(II) in acid solution takes place according to the equation: Fe(phen) 32+ + 3 H3O+ + 3 H2O → Fe(H2O) 62+ + 3 phenH+ If the activation energy,Ea,is 126 kJ/mol and the rate constant at 30°C is 9.8 × 10-3 min-1,what is the rate constant at 40°C?

Which general rate law below corresponds to an elementary bimolecular reaction?

The rate constant,k,for a first-order reaction is equal to 6.2 × 10-4 s-1.What is the half-life for the reaction?

What fraction of collisions will have sufficient energy to react for a gas whose activation energy is 68 kJ/mol at 25°C?

What is the rate law for the elementary reaction shown below? 2 HI → H2 + I2

The second-order reaction 2 Mn(CO) 5 → Mn2(CO) 10,has a rate constant equal to 3.0 × 109 M-1 s-1 at 25°C.If the initial concentration of Mn(CO) 5 is 5.0 × 10-5 M,how long will it take for 90.% of the reactant to disappear?

A three-step mechanism has been suggested for the formation of COCl2: 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 first-order reaction,SO2Cl2 → SO2 + Cl2,has a rate constant equal to 2.20 × 10-5 s-1 at 593 K.What percentage of the initial amount SO2Cl2 will remain after 3.00 hours?

The elementary reaction: 2 HF → H2 + F2,is an example of a ________ reaction.

The first-order reaction,SO₂Cl₂ → SO₂ + Cl₂,has a half-life of 8.75 hours at 593 K.How long will it take for the concentration of SO₂Cl₂ to fall to 14.5% of its initial value?

A gaseous reaction occurs by a two-step mechanism,shown below. Step 1: AX +Y₂ ⇌ AXY_{2 fast} Step 2: AXY₂ + AX → 2 AXY slow Including concentration of only reactants and products,what is the rate law for this reaction?

The isomerization reaction,CH₃NC → CH₃CN,is first order and the rate constant is equal to 0.46 s^-1 at 600 K.What is the concentration of CH₃NC after 0.20 minutes if the initial concentration is 0.40 M?

The first-order reaction,2 N₂O(g) → 2 N₂(g) + O₂(g) ,has a rate constant equal to 0.76 s^-1 at 1000 K.How long will it take for the concentration of N₂O to decrease to 6.0% of its initial concentration?

For the first-order reaction,2 N₂O(g) → 2 N₂(g) + O₂(g) ,what is the concentration of N₂O after 3 half-lives if mol of N₂O is initially placed into a 1.00-L reaction vessel?

The following reaction is first order,C₂H₆ → 2 CH₃.If the rate constant is equal to 5.5 × 10^-4 s^-1 at 1000 K,how long will it take for 0.35 mol of C₂H₆ in a 1.00 L container to decrease to 0.25 mol in the same container?

The rate constant,k,for a first-order reaction is equal to 6.2 × 10^-4 s^-1.What is the half-life for the reaction?

What is the rate law for the elementary reaction shown below? 2 HI → H₂ + I₂

The second-order reaction 2 Mn(CO) ₅ → Mn₂(CO) ₁₀,has a rate constant equal to 3.0 × 10⁹ M^-1 s^-1 at 25°C.If the initial concentration of Mn(CO) ₅ is 5.0 × 10^-5 M,how long will it take for 90.% of the reactant to disappear?

A three-step mechanism has been suggested for the formation of COCl₂: 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 first-order reaction,SO₂Cl₂ → SO₂ + Cl₂,has a rate constant equal to 2.20 × 10^-5 s^-1 at 593 K.What percentage of the initial amount SO₂Cl₂ will remain after 3.00 hours?

The elementary reaction: 2 HF → H₂ + F₂,is an example of a ________ reaction.