At 298 K, 0.01 M solution of ammonium hydroxide is 4.2% ionised. Calculate the ionisation constant of the base.

Explanation

To calculate the ionization constant (Kb) of ammonium hydroxide (NH4OH) given that a 0.01 M solution is 4.2% ionized at 298 K, we can follow these steps:

### Step 1: Determine the concentration of ionized species
Given that the solution is 4.2% ionized, we can calculate the concentration of the ionized species (NH4+ and OH-) in the solution.

- Ionization percentage = 4.2%
- Initial concentration of NH4OH (C) = 0.01 M

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