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Better method for preparation of BeF 2 , among the following is

1. BeO + C + F 2    BeF 2
2. (NH 4 ) 2 BeF 4    BeF 2
3. Be + F 2    BeF 2
4. BeH 2 + F 2    BeF 2

Correct answer: (NH 4 ) 2 BeF 4    BeF 2

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