Gram molecular mass of ammonia is:

The correct option is B 17g
The molecular formula of ammonia is $N{H}_3$. Gram molecular mass is the sum of gram atomic mass of all the atoms present in the molecule.

$\bullet$ Gram atomic mass of nitrogen = 14 g
$\bullet$ Gram atomic mass of hydrogen = 1 g

Gram molecular mass of ammonia ($N{H}_3$) = gram atomic mass of nitrogen + 3×gram atomic mass of hydrogen

Thus, gram molecular mass of ammonia = $14+(3\times 1)$ = 17 g