Question 19M.2.hl.TZ1.b
| Date | May 2019 | Marks available | [Maximum mark: 3] | Reference code | 19M.2.hl.TZ1.b |
| Level | hl | Paper | 2 | Time zone | TZ1 |
| Command term | Suggest | Question number | b | Adapted from | N/A |
Both vinegar (a dilute aqueous solution of ethanoic acid) and bleach are used as cleaning agents.
A solution of bleach can be made by reacting chlorine gas with a sodium hydroxide solution.
Cl2 (g) + 2NaOH (aq) ⇌ NaOCl (aq) + NaCl (aq) + H2O (l)
Suggest, with reference to Le Châtelier’s principle, why it is dangerous to mix vinegar and bleach together as cleaners.
[3]
ethanoic acid/vinegar reacts with NaOH [✔]
moves equilibrium to left/reactant side [✔]
releases Cl2 (g)/chlorine gas
OR
Cl2 (g)/chlorine gas is toxic [✔]
Note: Accept “ethanoic acid produces H+ ions”
Accept “ethanoic acid/vinegar reacts with NaOCl”.
Do not accept “2CH3COOH + NaOCl + NaCl → 2CH3COONa + Cl2 + H2O” as it does not refer to equilibrium.
Accept suitable molecular or ionic equations for M1 and M3.
The average score was 1 out 3. Many could not suggest why it is dangerous to mix chlorine with vinegar. Most students gained at least one mark for stating that “chlorine gas will be produced” but couldn’t link it to equilibrium ideas.
