Required Practical: Rates Of Reaction

Question 1

What reaction are we doing in this experiment?

Answer 1

Sodium thiosulfate solution + hydrochloric acid —> sulfur

Question 2

What are we aiming to do with this experiment?

Answer 2

Time how long it takes for the reaction to complete
Because sulfur is a solid and causes turbidity, it causes a drawn cross to disappear
So we can time how long it takes for the cross to disappear which is = to time for reaction

Question 3

Step 1

Answer 3

Put 10cm3 sodium thiosulfate in conical flask

Question 4

Step 2

Answer 4

Put conical flask on top of a printed black cross on paper

Question 5

Step 3

Answer 5

Add 10cm3 of hydrochloric acid into flask

Question 6

Step 5

Answer 6

Swirl solution and start a stopwatch

Question 7

Step 6

Answer 7

Look down through the top of the flask to see solution become cloudy and wait

Question 8

Step 7

Answer 8

Stop clock when we can no longer see the cross

Question 9

Step 8

Answer 9

Repeat using and lower concentrations of sodium thiosulfate solution

Question 10

Step 9

Answer 10

Repeat whole experiment
Calculate mean times of values for each concentration of sodium thiosulfate solution to fully react
Discard anomalies

Question 11

Independent variable

Answer 11

Concentrations of sodium thiosulfate solution

Question 12

Control variable

Answer 12

Volume of hydrochloric acid, temperature, concentration of hydrochloric acid

Question 13

Dependent variable

Answer 13

Time taken for cross to disappear
Aka time taken for sulfur to be produced after completing the reaction

Question 14

Problems with this experiment

Answer 14

Not reproducible, which means can be repeated by a different person using different equipment and get the same result
Because people have different eyesights as to when cross disappears