Common Test Practice Questions

Question 1

Which of the following substance cannot reduce iron(III) oxide to iron?

1: coke
2: hydrogen
3: carbon dioxide
4: carbon monoxide

Answer 1

3

Coke consists of carbon.
Carbon dioxide does not react with iron(III) oxide.

Question 2

An electrolysis of a metal chloride is conducted. A heat source is placed below the set-up to make it molten metal chloride. When the heat source was removed and the content was allowed to cool and solidify, no electric current is observed to flow.
A student made the following comment: “An electric current will be observed if water is added into the solution.” Explain if the student is correct.
[2m]

Answer 2

He is correct if the metal is Group 2 metal or copper or zinc. (0.5m)
All Group 2 metals or copper(II) or zinc chloride are soluble in water (0.5m) to form mobile ions as charge carriers. (1m)
He is incorrect if the metal is lead (0.5m) as PbCl2 is insoluble, thus will not form any mobile ions and electrons to carry electrical charges. (1m)