(i) Find the molecular mass of the following:
(a) `C_2H_6` (b) `PCl_3`
[Atomic masses: C = 12,C1 =35.5,H=1,P=31]
(ii) Find the formula mass of the following : (a) `KNO_3` (b) `CuSO_4.5H_2O`
[Atomic masses : K = 39, O = 16, N = 14, S = 32, Cu = 63.5, H = 1]

Explanation

To solve the question step by step, we will break it down into two parts: (i) finding the molecular mass of the given compounds and (ii) finding the formula mass of the specified ionic compounds.

### Part (i): Finding the Molecular Mass

**(a) For `C2H6`:**

1. Identify the number of atoms of each element in the compound:
- Carbon (C): 2 atoms
...