How is acetic acid converted separately to methylamine and ethyl amine? 

Explanation

On heating with ammonia, acetic acid gives acetamide. Acetamide on heating with bromine in presence of NaOH gives methyl amine and on reduction with `LiAlH_4` gives ethyl amine.
`CH_3CONH_2 underset(NaOH)overset(Br_2)toCH_3NH_2`
`CH_3CONH_2 overset(LiAlH_4) to CH_3 CH_2 NH_2`