11A - Rate Equations and Orders

Question 1

What is the order of a reactant?

Answer 1

The order of a reactant indicates how its concentration affects the rate of a chemical reaction.

Question 2

How is the order of a reactant represented in the rate equation?

Answer 2

The order of a reactant is denoted by a power to which its concentration is raised in the rate equation.

Question 3

What are the possible values for the order of a reactant?

Answer 3

The order can be positive, negative, or fractional. The values can be 0, 1 or 2.

Question 4

What does a fractional order suggest about a reaction?

Answer 4

It indicates that the reaction involves multiple steps.

Question 5

What happens when the order of reaction with respect to a reactant is 0?

Answer 5

Changing the concentration of the reactant has no effect on the reaction rate, and it is not included in the rate equation.

Question 6

What can be the possible explanation for why the order of a reactant is 0?

Answer 6

The concentration of this reactant can be greatly in excess so it does not affect the rate or this reactant may be absent in the rate determining step.

Question 7

Describe the order of reaction with respect to a reactant of 1.

Answer 7

The concentration of the reactant is directly proportional to the rate of reaction. Doubling the concentration doubles the rate. The reactant is included in the rate equation.

Question 8

Describe the order of reaction with respect to a reactant of 2.

Answer 8

The rate is directly proportional to the square of the concentration of that reactant. Doubling the concentration increases the rate by a factor of four. The reactant is included in the rate equation as a squared term.

Question 9

What is the overall order of reaction?

Answer 9

The overall order of reaction is the sum of the powers of the reactants in a rate equation.

Question 10

How is the rate equation derived from experimental data?

Answer 10

Determine orders with respect to each reactant by analyzing experiments where the concentration of one reactant changes while others remain constant.

Question 11

How can the rate constant (k) be calculated from initial rates and the rate equation?

Answer 11

Substitute initial rate and concentration values into the rate equation and solve for k.

Question 12

How is the progress of a reaction monitored to calculate the rate constant?

Answer 12

Measure initial rates using various initial concentrations of reactants.

Question 13

What are the units for constant k for different orders?

Answer 13

• Zero → mol dm-3 s-1
• First → s-1
• Second → dm3 mol-1 s-1
• Third → dm6 mol-2 s-1