Exam questions for Topic 3 (I think)

Question 1

3.8
Acids are a hazard if a high concentration of hydrogen ions is present. Hydrochloric acid is a strong acid, ethanoic acid is a weak acid. Explain why the hazard of the dilute hydrochloric acid is lower than the hazard of concentrated ethanoic acid, even though hydrochloric acid is a strong acid and ethanoic acid is a weak acid. [4 marks]

Answer 1

-Hydrochloric acid is fully dissociated into ions
-Ethanoic acid is only slightly dissociated into ions
-But the concentration of acid in the hydrochloric acid is lower
-So the concentration of hydrogen ions in the hydrochloric acid is lower.

Question 2

3.8
How do acids have the same concentration, but different pH?

Answer 2

-Acids with a low pH are strong acids
-Their molecules dissociate completely into ions when dissolved in water
-This produces a higher concentration of H+ ions, making it more acidic

Question 3

Explain what happens to the pH of the reaction mixture as calcium hydroxide continues to be added. [2 marks]

Answer 3

-Hydroxide ions REACTS with hydrogen ions
-They reduce the hydrogen ion concentration
-Therefore the pH increases
-Once all the acid has been neutralised, the pH will increase past pH 7 as excess hydroxide ions are added