Answers section
Questions 6.2
- State the uses of water and concentrated sulphuric (VI) acid in the set-up.
- Identify the four products in Flask 1.
- Write a complete formula equation for the reaction in Flask 1.
- Explain why this reaction is considered as a reduction-oxidation (redox) reaction.
- Complete the following equations for alternative reactions that also produce chlorine.
MnO2(s) + HCl(aq)PbO2(s) + HCl(aq)
Answers to Questions 6.2
- Water: It absorbs and therefore removes hydrogen chloride (HCl) gas released by concentrated hydrochloric acid. Concentrated sulphuric (VI) acid dries the gas by absorbing water vapour.
- Manganese (II) chloride (MnCl2)
Potassium chloride (KCl)
Water (H2O)
Chlorine (Cl2) - 2KMnO4(s) + 16HCl(aq) → 2MnCl2(aq) + 2KCl(aq) + 8H2O(l) + 3Cl2(g)
- Hydrogen is removed from its compound with chlorine (HCl); so chlorine is oxidized. Oxidation state of manganese reduces from +7 to +2; so manganese is reduced.
- MnO2(s) + 4HCl(aq)
MnCl2(aq) + 2H2O(l) + Cl2(g)
PbO2(s) + 4HCl(aq)PbCl2(aq) + 2H2O(l) + Cl2(g)
NB: Balancing long equations such as in Question 3 can be hectic. However, if you can recall one critical number, such as 16 on HCl, the rest will follow.