Answer : The balanced chemical equation will be:
(i) 
(ii) 
Explanation :
Balanced chemical equation : It is defined as the equation in which total number of individual atoms on the reactant side is equal to the total number of individual atoms on product side.
Part (i):
The balanced chemical equation will be:

This reaction is a single displacement reaction in which most reactive element (potassium) displaces the least reactive element (hydrogen) form their solution.
Part (ii):
The balanced chemical equation will be:

This reaction is a single displacement reaction in which most reactive element (zinc) displaces the least reactive element (magnesium) form their solution.
Answer:
See explanation
Explanation:
Given that the formula of the compound is Fe2O3, if a coefficient of 2 is placed in front of the formula, that is, if we write 2Fe2O3 . Then;
The number of Fe atoms becomes 2 *2 = 4
The number of oxygen atoms becomes 2*3 = 6
That is why the total number of iron atoms were written down as 4.