Chem 2 Exam

Chapter 13

100

What are the units of the rate of reactions?

Molerity per unit of time

200

How does a catalyst increase the rate of a chemical reaction?

Lowers the activation energy Ea of the reaction.

300

The decomposition of a certain compound A follows first-order kinetics according to the equation:

A→Products

At 25 C, the rate constant for this reaction is 0.015 s^-1. If the initial concentration of A is 0.10 M, calculate:

1. The concentration of A after 60 seconds.

after 60 seconds, the concentration of A is approximately 0.041 M.

400

The decomposition of a certain compound A follows first-order kinetics according to the equation:

A→Products

At 25 C, the rate constant for this reaction is 0.015 s^-1. If the initial concentration of A is 0.10 M, calculate:

1. The half-life of the reaction.
2. The time required for A to decompose to 25% of its initial concentration.

the half-life of the reaction is approximately 46.2 seconds.

 it takes approximately 92.7 seconds for A to decompose to 25% of its initial concentration.

500

The reaction between nitrogen dioxide (NO₂) and carbon monoxide (CO) to form nitrogen monoxide (NO) and carbon dioxide (CO₂) is believed to follow the following rate law:

Rate=k[NO₂]^m[CO]ⁿ

At a certain temperature, the initial rate of the reaction was measured for various initial concentrations of NO₂ and CO, yielding the following data:

[NO2]0(M) ---    [CO]0(M)  ----  Initial Rate(M/s)        0.10    ---       0.20          ---          3.0×10^-3       0.20 --          0.20 --                     2.4×10^-2       0.10 --          0.40 --                    6.0×10^-3 

Determine the rate law expression for the reaction and the values of k, m, and n.

Rate=1.5[NO2][CO], and the values of k, m, and n are 1.5 M^-1s^-1 , 1, and 0, respectively. 

Chapter 14 and 15

100

In the following Equilibrium system:

HF + H₂O -> H₃O⁺ + F^- 

Which of the Following are Bronsted Acids?

 H₃O⁺ and HF 

200

In the following Equilibrium system:

CH₃OOH + CH₃NH₂ -> CH₃NH₃⁺ + CH₃OO^- 

Which of the Following are Bronsted bases?

CH₃OO^- and  CH₃NH₂

300

For the following equilibrium process:

4Fe (s) + 3O₂ (g) → 2Fe₂O₃(s)  ΔH⚬ = - 1648 kJ/mol

Predict the direction of the reaction when:

A) 4Fe (s) is added

B) The equilibrium mixture is heated

A) Nothing

B) Reverse

400

Consider the following reaction at equilibrium:

2SO₂(g)+O₂(g)⇌2SO₃(g)

At a certain temperature, a 2.0 L reaction vessel initially contains 0.50 mol of SO₂, 0.30 mol of O₂, and 0.10 mol of SO₃. If the equilibrium constant Kc for the reaction at this temperature is 2.0×10³, determine:

1. The concentrations of SO₂, O₂, and SO₃ at equilibrium.

1. The concentrations of SO₂, O₂, and SO₃ at equilibrium are 0.43 M0.43M, 0.27 M0.27M, and 0.17 M0.17M respectively.

500

At a  temperature 298 K, the equilibrium constant Kp for the reaction

2SO₂(g)+O₂(g)⇌2SO₃(g)

is 3.0×10⁴ atm^-1 

Calculate the equilibrium constant Kc for the reaction at the same temperature.

Kc for the reaction is approximately 1227.7