Factors Affecting the Rate of Reaction

Question 1

Using powdered marble instead of marble chips increases the rate of reaction because it:

Accepted Answer

increases the total surface area — Powder has a much larger total surface area than lumps of the same mass, exposing more particles to collision.

Question 2

Which change would NOT increase the rate of reaction between zinc and dilute sulphuric acid?

Accepted Answer

Using larger zinc lumps instead of powder — Larger lumps have a smaller total surface area than powder, so the rate would decrease, not increase.

Question 3

A catalyst increases the rate of reaction by:

Accepted Answer

providing an alternative path with lower activation energy — A catalyst offers a lower-energy route so a larger fraction of collisions have enough energy to react.

Question 4

Increasing the temperature increases reaction rate mainly because:

Accepted Answer

a larger fraction of particles have energy above the activation energy — Higher temperature raises kinetic energy so more collisions exceed the activation energy, and collisions are also more frequent.

Question 5

The same reaction as lumps takes 80 s and as powder takes 20 s. How many times faster is the powder reaction?

Accepted Answer

4 times — Rate ∝ 1 ÷ time, so ratio of rates = 80 ÷ 20 = 4 times faster.

Question 6

Increasing the pressure of a reacting gas mixture increases the rate because it:

Accepted Answer

brings gas particles closer together — Higher pressure squeezes gas particles into a smaller volume, so collisions become more frequent, like raising concentration.

Question 7

Which statement about a catalyst is correct?

Accepted Answer

It remains chemically unchanged at the end — A catalyst speeds up the reaction but is not consumed and is recovered chemically unchanged.

Question 8

Doubling the concentration of an acid increases the rate because there are:

Accepted Answer

more reactant particles per unit volume — Higher concentration means more reactant particles in the same volume, so collisions are more frequent.

Question 9

Which factor usually has NO effect on a reaction between two solids with no solution or gas involved?

Accepted Answer

Concentration of a solution — If no solution is present, concentration cannot be defined or changed, so it has no effect.

Question 10

For the reaction Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g), which gas is released faster when the acid is warmed?

Accepted Answer

Hydrogen, H2 — The reaction produces hydrogen gas; warming increases the rate so H2 is released faster.

The main factors

A comparison experiment