Rates of reaction

Question 1

The equation for the reaction is:
sodium thiosulfate + hydrochloric acid → sodium chloride + water + sulfur dioxide + sulfur
Explain why the solution goes cloudy. [2]

Answer 1

• sulfur forms…

- …which is solid / a precipitate

Question 2

State the effect that increasing the temperature of the sodium thiosulfate solution has on the rate of the reaction.
Explain this effect in terms of particles and collisions. [4]

Answer 2

• rate increases…
• …because particles move faster…
• …so particles are more likely to collide
• more particles have energy greater than the activation energy

Question 3

Explain, in terms of particles and collisions, the effect that increasing the surface area has on the rate of reaction. [2]

Answer 3

• the rate increases…

- …because of more frequent collisions between particles

Question 4

Give one reason why using a catalyst reduces costs. [1]

Answer 4

• it increases the rate of reaction
• it reduces the energy required
• lower temperatures can be used
• catalysts don’t get used up

Question 5

Suggest one improvement the student could make to the apparatus when investigating the temperature change. [2]

Answer 5

• add a lid…
• …to reduce / stop heat loss
• use a digital thermometer…
• …for more accurate data

Question 6

State the effect of increasing the pressure on the rate of reaction.
Explain your answer in terms of particles. [3]

Answer 6

• rate increases…
• …because particles are closer together…
• .., so particles are more likely to collide

Question 7

What is meant by the activation energy? [1]

Answer 7

the (minimum) amount of energy (particles must have) to react