Chemical Kinetics and Chemical Equilibria

Question 1

Slowest step of a reaction is called the

Answer 1

rate determining step

Question 2

Rate =

Answer 2

change in concentration / time

Question 3

Rate = k[A]^x [B]^y

What is this equation and explain.

Answer 3

• rate law expression
• A and B are concentrations of the reactants
• k is rate constant
  x and y exponents are orders of reaction
• these exponents must be determined experimentally!!!

Question 4

Reaction orders

Answer 4

• depending on the chemical reaction, the kinetics have different orders
• zero, first order, second order, higher order reactions

Question 5

What are 4 factors that affect reaction rate

Answer 5

• concentration of reactants
• temperature
• medium
• catalysts

Question 6

Keq = [C]c[D]d / [A]a[B]b

Answer 6

law of mass action

rates forward and rates reverse are equil at equilibrium

Question 7

Define Keq and its properties

Answer 7

equilibrium constant:
- pure solids and liquids do not appear in the equilibrium constant expression
Keq is at a given temp
- Keq less than 1 (less products) and vice versa

Question 8

What is Q

Answer 8

reaction quotient.
- at any time of the reaction you can measure the conc. of reactants and products and calculate the reaction quotient and compare with Keq

Question 9

If Q is less than Keq then reaction…

Answer 9

proceeds forwards towards equilibrium

- there are more reactants than at equilibrium

Question 10

If Q is greater than Keq then reaction…

Answer 10

forward reaction exceeded equilibrium

greater products present than at equilibrium

Question 11

Le Chatelier’s change in concentration shifts

Answer 11

• increasing conc. of species will shift equilibrium to reestablish the equilibrium conc.
• add; shift away from what you added
• remove; shift towards what you took away

Question 12

Le Chatelier’s Pressure and Volume

Answer 12

• liquids and solids are incompressible so change has no effect on equilibrium
• inversely related
• increase pressure = decrease volume; shift to decrease moles present (shift to side with less moles)
  vice versa

Question 13

Le Chatelier’s Temperature

Answer 13

• consider heat as a product (exothermic - release heat) or reactant (endothermic - produced heat)
• replace heat lost if temperature is decreased
• if temperature is increased, shift towards other side to balance out the heat