Reaction of BeO with ammonia and hydrogen fluoride gives A which on thermal decomposition gives `BeF_2` and `NH_4F`. What is 'A' ?

Options

A. ` (NH_4)BeF_3`
B. `H_3NBeF_3`
C. `(NH_4)Be_2F_5`
D. `(NH_4)_2BeF_4`

Answer

To solve the problem step by step, we need to analyze the reaction of beryllium oxide (BeO) with ammonia (NH₃) and hydrogen fluoride (HF) to identify the compound 'A' that is formed.

### Step 1: Write the Reactants
We start with the reactants:
- Beryllium oxide (BeO)
- Ammonia (NH₃)
- Hydrogen fluoride (HF)

### Step 2: Identify the Reaction
When BeO reacts with NH₃ and HF, it forms a complex compound. The reaction can be represented as:
\[ \text{BeO} + 2 \text{NH}_3 + 4 \text{HF} \rightarrow \text{NH}_4\text{BeF}_4 + \text{H}_2\text{O} \]

### Step 3: Identify Compound 'A'
From the reaction, we see that the product formed is:
\[ \text{A} = \text{NH}_4\text{BeF}_4 \]
This is the compound we are looking for.

### Step 4: Thermal Decomposition of 'A'
Next, we need to consider the thermal decomposition of compound 'A':
\[ \text{NH}_4\text{BeF}_4 \xrightarrow{\text{heat}} \text{BeF}_2 + \text{NH}_4\text{F} \]

### Conclusion
The compound 'A' formed from the reaction of BeO with NH₃ and HF is:
\[ \text{A} = \text{NH}_4\text{BeF}_4 \]

### Final Answer
The answer to the question is:
**A = NH₄₂BeF₄**

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