GCSE Chemistry CA - Past Paper Questions

Question 1

Q2) Use your results and information from your graph to explain what you found out in your investigation and whether this agreed with the hypothesis you made at the start of your investigation.
(5 marks)

Answer 1

• We found out that as you increase the volume of hydrochloric acid used, more sodium hydroxide solution is needed to neutralise it.
• Provide evidence from your results: e.g when I use (blank) cm^3 of HCl, (blank) cm^3 of NaOH is needed to neutralise it. (x2)
• This agrees with my hypothesis which states…
• The reason: If I use more HCl, then more H+ ions are present in solution, so more OH- ions are needed to neutralise them:

H+ (aq) + OH- (aq) —-> H2O (l)

Question 2

Q3) a) Explain how you ensured that your investigation was a fair test. (2 marks)

Answer 2

• Only one factor, the independant variable, i.e the volume of hydrochloric acid is changed
• All other factors, controlled variables, i.e concentration of HCl, concentration of NaOH, remained constant

Question 3

Q3) b) What was the range of measurements?

Answer 3

The range of measurements for the hydrochloric acid was from 5 cm^3 up to 25 cm^3.

The range of measurements for the sodium hydroxide solution were from (X - lowest) cm^3 up to (Y - highest) cm^3

Question 4

Q4) Did you have any anomalous results? Use your results and/or information from your graph to support your answer.

Answer 4

An anomalous result is one which does not follow the trend of the graph/results (1 mark)

Point B, at 10 cm^3 of HCl, required X amount of NaOH. This does not follow the trend of the results or the line of best fit, and is therefore anomalous. (1 mark)

OR

There were no anomalous results in our investigation, all results fitted the pattern/trend of the graph. (1 mark)

Question 5

How was our investigation reliable?

Answer 5

We repeated the experiment multiple times

We calculated an average of our results

Question 6

How was our experiment accurate?

Answer 6

We measured out the required volume of acid using a burette rather than a measuring cylinder

Question 7

Give two examples of strong acids

Answer 7

Hydrochloric acid

Sulfuric acid

Question 8

Give two examples of weak acids

Answer 8

Nitric acid
Ethanoic acid (Acetic acid)

Question 9

Give the formula for ethanoic acid (acetic acid)

Answer 9

CH3COOH

Question 10

Give the formula for nitric acid

Answer 10

HNO3

Question 11

Give the formula for hydrochloric acid

Answer 11

HCl

Question 12

Give the formula for sulfur if acid

Answer 12

H2SO4