Rate of Reaction

Question 1

Increasing the temperature of a reaction usually:

Accepted Answer

increases the rate — Higher temperature means faster, more energetic collisions, so the rate increases.

Question 2

Increasing the concentration of a reactant in solution:

Accepted Answer

speeds the reaction up — More particles per unit volume gives more frequent collisions, so the rate rises.

Question 3

Using a powder instead of large lumps of the same solid makes the reaction faster because:

Accepted Answer

the surface area is larger — A powder exposes more surface, so more collisions occur per second.

Question 4

A catalyst is a substance that:

Accepted Answer

speeds up a reaction without being used up — A catalyst provides a lower-energy pathway and is chemically unchanged at the end.

Question 5

According to collision theory, a reaction occurs when particles collide:

Accepted Answer

with at least the activation energy — Colliding particles must have enough energy to react, called the activation energy.

Question 6

A reaction makes 60 cm³ of gas in 30 s. The average rate is:

Accepted Answer

2 cm³/s — Rate = volume ÷ time = 60 ÷ 30 = 2 cm³/s.

Question 7

Which method can be used to follow a reaction that produces a gas?

Accepted Answer

Measuring the volume of gas collected over time — Collecting the gas and recording its volume against time gives the rate.

Question 8

A catalyst increases the rate of reaction by:

Accepted Answer

lowering the activation energy — A catalyst offers an alternative route with a lower activation energy, so more collisions succeed.

Question 9

On a graph of gas volume against time, the fastest rate is shown by the part of the line that is:

Accepted Answer

steepest — The steeper the gradient, the more gas is produced per second, so the rate is greatest.

Question 10

Why does raising the temperature increase the rate of reaction?

Accepted Answer

Particles collide more often and with more energy — Hotter particles move faster, so collisions are more frequent and more of them exceed the activation energy.

What is the rate of reaction?

Collision theory