Older MCQs might not have the typical A, B, C,
D
choices. They
have choices 1, 2, 3, and a combination of them is the answer. Below is the key that maps such
combinations to the answer.
A
1, 2 and 3 are correct
B
1 and 2 only are correct
C
2 and 3 only are correct
D
1 only is correct
State the symbol equations for the extraction of iron from hematite (a) ( C + O_2
ightarrow CO_2 ) (b) ( C + CO_2
ightarrow 2CO ) (c) ( Fe_2O_3 + 3CO
ightarrow 2Fe + 3CO_2 ) (d) ( CaCO_3
ightarrow CaO + CO_2 ) (e) ( CaO + SiO_2
ightarrow CaSiO_3 )
Describe the reactions, if any, of: (a) potassium, sodium and calcium with cold water (b) magnesium with steam (c) magnesium, zinc, iron, copper, silver and gold with dilute hydrochloric acid and explain these reactions in terms of the position of the metals in the reactivity series
Identify redox reactions by changes in oxidation number using: (a) the oxidation number of elements in their uncombined state is zero (b) the oxidation number of a monatomic ion is the same as the charge on the ion (c) the sum of the oxidation numbers in a compound is zero (d) the sum of the oxidation numbers in an ion is equal to the charge on the ion
