C3c - Rate of reaction (3)

Question 1

What is a catalyst

Answer 1

a substance which changes the rate of reaction and is unchanged at the end of the reaction

Question 2

Why is only a small amount of a catalyst needed to catalyse large amounts of reactants

Answer 2

it is not used up during the reaction so can be can be used over and over again

Question 3

Why may a catalyst not be able to catalyse different reactions

Answer 3

each catalyst is specific to a particular reaction

Question 4

Explain the difference in rate of reaction between a lump and powdered reactant (2)

Answer 4

powdered reactant is broken up into smaller pieces, so has more surface area than lump

particles around it have more surface area to work on and the powders can spread throughout a reaction mixture, therefore increasing the collision frequency, and increasing the rate of reaction

Question 5

Explain the dangers of fine combustible powders in factories (e.g. custard powder, flour or sulfur)(2)

Answer 5

they burn easily and explosively in air because of their higher surface area and high rate of reaction

care must be taken to stop dust escaping into the air inside buildings, and to
prevent sparks or naked flames from being near the powders