Reaction Rates & Kinetics — Drills · Grade 11 Science

Chapter: Rates & Equilibrium

What these drills covers

By the end of Reaction Rates & Kinetics you should be able to:

I can use collision theory to explain what must happen for particles to react.
I can predict how concentration, temperature, surface area, and catalysts change the rate of a reaction.
I can calculate an average reaction rate from the change in an amount over time.

6 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: reaction rate, collision theory, effective collision, catalyst, surface area, inhibitor.

Problem 1

Which change will slow a reaction down?

lowering the concentration of a reactant
adding a catalyst
raising the temperature
grinding a solid into a fine powder

Answer and explanation

lowering the concentration of a reactant

Lowering the concentration spreads particles out, so fewer effective collisions occur per second and the reaction slows.

Problem 2

A catalyst speeds up a reaction by…

raising the activation energy
lowering the activation energy
being used up quickly
increasing ΔH

Answer and explanation

lowering the activation energy

A catalyst provides an alternate pathway with a lower activation energy, so more collisions are effective — and it is not consumed.

Problem 3

A reaction produces 150 mL of gas in 30 s. What is the average rate of gas production in mL/s?

Answer and explanation

5 mL/s

Average rate = 150 mL ÷ 30 s = 5.0 mL/s.

Problem 4

Why does increasing the surface area of a solid reactant speed up a reaction?

it acts as a catalyst
it raises the temperature of the solid
it exposes more particles, so more collisions can occur at once
it lowers the activation energy

Answer and explanation

it exposes more particles, so more collisions can occur at once

More exposed surface means more reactant particles are in contact, so more effective collisions can happen per second.

Problem 5

Using collision theory, explain why increasing the concentration of a reactant speeds up a reaction.

Answer and explanation

Higher concentration packs more reactant particles into the same volume, so collisions between particles happen more often. More collisions per second means more effective collisions per second, which speeds up the reaction.

Problem 6

During a reaction, 0.48 mol of a reactant is consumed in 60 s. What is the average rate of consumption in mol/s?

Answer and explanation

0.008 mol/s

Rate = 0.48 mol ÷ 60 s = 0.008 mol/s.

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