Kinetics

Question 1

What is the mathematical relationship between K_c and K_p?

Answer 1

K_c = K_c (RT)^Δn

Δn = (moles of gaseous products) - (moles of gaseous reactants)

Remember that K_p expressions use partial pressures of gaseous state reactants/products instead of concentrations

Question 2

What does it mean if the equilibrium constant is much lower than the reaction quotient?

(K_c < Q_c)

Answer 2

That the reaction will proceed in the reverse direction (towards the reactants), in order to reach a state of equilibrium.

Question 3

What does K_c «1 tell us about a given reaction?

Answer 3

That the reactants are generally favored.

Question 4

What does it mean if the equilibrium constant is much higher than the reaction quotient?

Answer 4

That the reaction will proceed in the forward direction (towards the products) to reach a state of equilibrium.

Question 5

How do catalysts speed up a reaction?

Answer 5

A catalyst will lower the activation energy (E_a) for a given reaction by providing a new mechanistic route that requires less overall energy to create product(s).

Question 6

How will increasing temperature of an endothermic reaction affect the reaction rate?

Answer 6

Adding heat energy to an endothermic reaction will increase the reaction rate.

Question 7

If the following reaction is third order in regard to carbon monoxide (CO), what happens to the rate if the concentration of CO is doubled?

CO_(g) + O_2(g) → CO_2(g)

Answer 7

The reaction rate is multiplied by a factor of eight.

Becuase the reaction order in regard to CO is third order, and we’re increasing the concentration of CO by a factor of two….

2³ = 8

Question 8

What function of the concentration for reactant [A] in a first order reaction gives a linear line-graph?

Answer 8

Plotting the natural log of the concentration of A gives a straight line:

f(x) = Ln([A])

Question 9

For a zero order reaction, how does the rate change as the concentration of the reactant(s) is(are) doubled?

Answer 9

In a zero order reaction, the rate is independent of the concentration of the reactant(s). Therefore, the rate will not change due to a change in concentration of reactant(s).

Question 10

What is the rate equation(s) for a second order reaction?

Answer 10

r = k[A][B]
(because A and B are raised to the first power and exponents are added together when their bases are multiplied)

or

r = k[A]^2</sub>

Question 11

What is the half-life equation for a first order reaction?

Answer 11

t_1/2 = 0.693/k

Question 12

What is the rate equation for a first order reaction?

Answer 12

r = k[A]