Why excess of `NH_(4)OH` is used in precipitating the sulphides of group IV cations?

Explanation

To answer the question of why excess of `NH4OH` (ammonium hydroxide) is used in precipitating the sulphides of group IV cations, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Understanding Group IV Cations**:
Group IV cations include metals such as zinc (Zn²⁺), manganese (Mn²⁺), nickel (Ni²⁺), and cobalt (Co²⁺). These cations can form insoluble sulphides when combined with sulphide ions (S²⁻).

**Hint**: Remember that group IV cations are typically more soluble than group II cations, which is important for understanding the precipitation process.
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