Module 5.1 - Rates, Equilibrium, and pH

Question 1

What is Rate of Reaction?

Answer 1

How fast reactants are converted into products

Question 2

What does rate depend on?

Answer 2

• Concentrations of reactant

- Rate constant

Question 3

What is the equation for rate of reaction?

Answer 3

A + B -> C + D

Rate = k[A]^m[B]^n

Question 4

What does m and n show in the equation

Rate = k[A]^m[B]^n

Answer 4

The order of reaction with respect to that species

Can be either 0, 1, or 2

Question 5

How do you calculate total reaction order?

Answer 5

m + n

Question 6

What are the units for rate of reaction?

Answer 6

mol dm-3 s-1

Question 7

What is the rate constant? (K)

Answer 7

• Relates to the concentrations of the species that affect the rate of a reaction to the overall rate of reaction
• Constant when temperature remains constant.

Question 8

How do you find K in a reaction?

Answer 8

Rearrange rate equation

k = rate / [A]^m[B]^n

Question 9

How are zero, first, and second order species shown on concentration-rate graphs?

Answer 9

Zero = Horizontal 
First = Diagonal upwards
Second = curving upwards

Question 10

What does Zero order mean?

Answer 10

The concentration of the species has no impact on the rate

rate = k

Question 11

What does First order mean?

Answer 11

The concentration of the species and the rate are directly proportional - double conc. doubles rate
rate = k[A]

Question 12

What does Second order mean?

Answer 12

• Rate is proportional to the concentration of the species squared
• Doubling conc. will quadruple the rate
• Rate = k[A]²

Question 13

How are zero, first, and second order species shown on concentration-time graphs?

Answer 13

zero = linear diagonal down
first = curved downwards
second = curved downwards with a kink in the line

Question 14

How would you write a rate equation for A, B, and C, A being 1st order, B being 0 order, and C being 2nd order?

Answer 14

Rate = k[A][C]^2

Question 15

What is half life?

Answer 15

The time taken for the initial concentration of the reactants to decrease by half.

Question 16

How do you determine half life of a reactant?

Answer 16

From a concentration-time graph, each time the concentration halves.
e.g. if starting conc = 1.8, 1st half life = 0.9, 2nd half life = 0.45, etc.

Question 17

What are the 2 general ways to investigate rate of reaction at given times

Answer 17

• Measuring change in a reactant mass or concentration over time
• Measuring change in a product mass or concentration over time

Question 18

How do you obtain a concentration-time graph through titration?

Answer 18

• Remove small samples of a mixture at regular intervals throughout reaction
• Titrate samples to determine concentration of a given reactant or product at that time

Question 19

What is the Rate determining step?

Answer 19

the slowest step in a reaction, that determines the overall rate