Required Practical 3: Investigation of how the rate of a reaction changes with temperature

Question 1

Sodium thiosulfate solution (NA2S2O3) reacts with dilute hydrochloric acid, becoming turbid
Describe a method to investigate the impact of temperature on the initial rate of reaction and an explanation of how you would handle the data recorded
(Explain practical 3, applying it to these chemicals)

Answer 1

1/ Use water baths to heat separate samples of NA2S2O3 and HCl to 25, 35, 45 and 55 degrees celcius

2/ Mark an x on a piece of paper and place the water bath over it

3/ Add first sample of HCl to first sample of NA2S2O3 and start the timer

4/ Record time taken for cross to disappear

5/ Repeat experiment using water bath at 34 degrees celsius, keeping the same volumes and concentrations

6/Calculate 1/t for each temperature

7/ Then plot time against 1/t on a graph

Question 2

Why does rate of reaction increase with increasing temperature?

Answer 2

As temperature increases, the kinetic energy of the molecule increases. Meaning more molecules have energy greater than the activation energy can therefore react

Also as kinetic energy of molecules increases, their velocities increase resulting in more frequent and successful collisions

Question 3

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

Answer 3

1/ Concentrations of reactants and products

2/ Volumes of reactants and products

3/ Using the same beaker and cross underneath

4/ Using the same person to decide when the cross has disappeared

Question 4

How can you keep a substance at a constant temperature?

Answer 4

Using a water bath keeps the temperature constant. For this experiment you can set up water baths of different temperature to see how they affect the rate of reaction