Question

How many atoms are there in $4.25 \,g$ of $NH_3$ ?

• A. $ 6 \times 10^{23}$
• B. $ 1.5 \times 10^{23}$
• C. $3.4 \times 10^{23}$
• D. $ 1 \times 10^{23}$

Answer 1

Answer: (A)

The no. of molecules
$=\frac{\text { Given mass }}{\text { Molar mass }} \times NA =\frac{4 \cdot 25}{17} \times 6 \cdot 022 \times 10^{23} $
$=1.5055 \times 10^{23}$
One molecules of $NH _3$ has 4 atom.
Hence no. of atoms $=1 \cdot 5055 \times 10^{23} \times 4$
$=6 \cdot 022 \times 10^{23}$