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 )
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
