Chemical Equilibrium
Rate Laws/Half-Life
Arrhenius Equation
General
100

What is equilibrium defined as?

When the rate of the forward reaction equals the rate of the reverse reaction

100

What are the units of k in the following rate law?

Rate = k [A]5[B]1/2[C]7

M-11.5 s-1

100

The rate constant for a reaction at 387 K is 4.40×10-3 s-1. The activation energy is 102 kJ/mol. Calculate the rate constant at 492 K.

K2 = 3.82 s-1

100

How does temperature affect the reaction rate?


Increasing will increase the rate, decreasing will decrease the rate

200

What is the equilibrium constant (Kc) for the following reaction?

aA + bB <-> cC + dD

Kc = [C]C [D]d/[A]a [B]b

200

*savannah pull up picture

For the following reaction, determine the orders of A and B and write the rate law.

2A (g) + B (g) -> C (g) + D (g)

A and B: 2nd order, Rate = k[A]2[B]2

200

For a reaction, the rate constant at 298 K is 4.12×10-3 s-1, and at 318 K, the rate constant is 8.27×10-3 s-1. Calculate the activation energy of the reaction in kJ/mol.

27.4 kJ/mol

200

How do catalysts affect a reaction?

Positive catalysts lower activation energy and increase the rate, negative catalysts raise activation energy and decrease the rate.

300

Determine the value of Kc for the following reaction. [A] = 8.9 x 10-4, [B] = 2.5 x 10-4, [C] = 5.6 x 10-5.

3A(g) + 2B(g) ⇌ 1/2C(g)

Kc = 1.7 x 1014
300

For a second-order reaction, the rate constant is k = 1.21 x 10⁻³ M⁻¹s⁻¹. If the initial concentration is 0.776 M, calculate the concentration of the substance after 137 seconds.

0.688 M

300

The rate constant for a reaction at 453 K is 3.5×10-4 s and the activation energy is 97 kJ/mol. Calculate the temperature when the rate constant is 1.2×10-2 s-1.

T = 525 K
300

What values of Kc favor products and what values favor reactants?

Larger than 1, favors products, smaller than 1, favors reactants

400

The reaction below has a Kp value of 1.70 x 10^4. What is the value of Kc for this reaction at 557 K? 

N2(g)+3H2(g)⇌2NH3(g)

Kc = 372

400

The half-life of a first-order substance is 71 seconds. If its initial concentration is 5.71 x 10^(-4) M, after 19.2 seconds, how much of the substance is left? If the final concentration is 3.92 x 10^(-4) M, how much time has elapsed?

4.73 x 10-4 M, 38.5 seconds

400

A certain reaction has an activation energy of 68 kJ/mol. The rate constant at 207 K is 3.95 × 10-3 s-1. Calculate the rate constant at 247 K.

K = 2.37 s-1

400
In an exothermic reaction, how does an increase in temperature affect equilibrium? What about in an endothermic?

Exothermic: shifts to the left (reactants)

Endothermic: shifts to the right (products)

500
  1. 2A(g)+ B(g) ⇌ C(g) Kc 1=4.5
  2. 2D(g)+E(g) ⇌ C(g) Kc 2=2.3

Find the equilibrium constant for the overall reaction:

4A(g)+ 2B(g) ⇌ 4D(g) + 2E(g)

Kc = 3.8

500

The zero-order decomposition of substance B has a half-life of 468 seconds, what is the initial concentration if its rate constant is 8.74 x 10^(-4) M s^(-1)? How much will remain after 307 seconds? How much time has elapsed when the final concentration is 0.112 M?

Initial: 0.818 M, Final: 0.550 M, Time: 808 seconds

500

The rate constant for a reaction at 273 K is 1.5×10-6 s-1 and at 298 K, it is 3.2×10-3 s-1. Calculate the activation energy for the reaction in kJ/mol. Also, determine the rate constant at 310 K

Ea = 207 kJ/mol, rate constant at 310: 8.17 x 10-2 s-1

500

What is the relationship between a reaction rate and the value of Kc?

There is none! (sorry it was a trick)

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