RP3: Effect of Temperature on Rate of Reaction

Question 1

How can rate of reaction be measured?

Answer 1

Initial rate method - Iodine clock reaction

Continuous monitoring method - measuring the volume of gas released in a reaction over time.

Question 2

Why does rate of reaction increase with increasing temperature?

Answer 2

Temp increase = kinetic energy increases = more molecules have energy greater than the activation energy.

Question 3

How would you investigate how rate of reaction varies with temperature?

Na2S2O3 (aq) + 2HCl (aq) -> 2NaCl (aq) + SO2 (g) + S (g)

Answer 3

This reaction produced a cloudy precip. of sufur

Easy method: To measure rate by timing how long it takes for a cross marked underneath the beaker to disappear, using a stopwatch. The sulphur precipitate produced prevents you from seeing the cross.

Repeat this at 5+ different temp (room temp, 25oc, 35oc, 45oc, 55oc) and compare times taken.

the temperature must not exceed 55oC.

Question 4

What are some issues with this method?

Answer 4

Judged by eye = unreliable

Delayed reaction time with stopwatch.

Low temp = reaction too slow

Not enough precip for cross to disappear.

Question 5

How could you analyse the data?

Answer 5

For a graph of the amount of sulphur against time, it would be a straight line at the beginning as the reaction has only just begun.

gradient of this straight section = rate of reaction

Question 6

What is a control variable?

Answer 6

A variable that is kept constant throughout the experiment

Question 7

In an experiment investigating the effect of temperature on rate of reaction, what variables will you control?

Answer 7

• conc of reactants and products
• volumes of reactants and products
• use the same beaker and cross underneath
• use the same person to decide when the cross has disappeared

Question 8

How can we keep a substance at a constant temperature?

Answer 8

Using a water bath keeps the temperature constant. For this experiment, you can set up water baths at different temperatures to see how it affects the rate of reaction.

Question 9

Define the rate of Reaction

Answer 9

change in the amount of a reactant or product over time.

Question 10

Formula for rate of reaction and units

Answer 10

rate of reaction = amount of reactant or product formed
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time
units e.g. g s-1 or cm3 s-1