Practicals

Question 1

6 Marker: Describe the full method for investigating how concentration affects the rate of reaction using sodium thiosulfate and hydrochloric acid. Include equipment, steps, and variables.

Answer 1

• Place a conical flask on a paper with a black cross drawn on it.\n- Add 50 cm³ sodium thiosulfate solution to the flask.\n- Add 10 cm³ hydrochloric acid and start the timer immediately.\n- Watch the cross through the flask and stop the timer when the cross is no longer visible.\n- Repeat using different concentrations of sodium thiosulfate (diluted with water).\n- Keep volume of acid and temperature the same each time.

Question 2

What is the independent variable in the rate of reaction practical with sodium thiosulfate and hydrochloric acid?

Answer 2

The concentration of sodium thiosulfate.

Question 3

What is the dependent variable in the rate of reaction practical?

Answer 3

The time taken for the cross to disappear / the rate of reaction.

Question 4

How does increasing the concentration of acid or sodium thiosulfate affect the rate of reaction?

Answer 4

It increases the number of particles in the same volume, so there are more frequent successful collisions, increasing the rate.

Question 5

Name two variables you must keep the same (control variables) in the rate of reaction practical.

Answer 5

Volume of acid and temperature (also same person timing for consistency).

Question 6

6 Marker: Describe the full method for separating inks using paper chromatography. Include steps, reasons, and how to calculate Rf.

Answer 6

• Draw a pencil line near the bottom of chromatography paper.\n- Place small spots of ink on the line.\n- Stand the paper in a small amount of solvent, below the pencil line.\n- Allow the solvent to travel up the paper until near the top.\n- Remove the paper and let it dry.\n- Measure how far each spot and the solvent moved.\n- Calculate Rf = distance moved by substance ÷ distance moved by solvent.

Question 7

Why is the line drawn in pencil during paper chromatography?

Answer 7

Because pencil is insoluble and won’t dissolve or affect the results.

Question 8

How do you calculate the Rf value in chromatography?

Answer 8

Rf = distance moved by substance ÷ distance moved by solvent.

Question 9

Why do different substances travel different distances in chromatography?

Answer 9

Because they have different solubilities in the solvent and different attractions to the paper.

Question 10

Name two control variables in the chromatography practical.

Answer 10

Type of solvent and size of the ink spots.

Question 11

Purifying water practical

Answer 11

Aim- Produce potable water by distillation

Use a Bunsen burner to boil water in a conical flask with a bung and tube leading to a test tube in a beaker of ice. Due to the colder temperature, the evaporated water will condenser, leaving the salt and impurities behind. This is a form of desalination.