# Question #407ab

Jul 18, 2017

We know that ${N}_{A}$ ammonia molecules have a mass of $17.03 \cdot g$. And thus the number of atoms in a $4.25 \cdot g$ mass of AMMONIA is $6.01 \times {10}^{23}$, i.e. $\text{Avocado's number of atoms.}$

#### Explanation:

We work out (i) the molar quantity of ammonia:

$= \frac{4.25 \cdot g}{17.03 \cdot g \cdot m o {l}^{-} 1} = 0.250 \cdot m o l$

And (ii), we were axed for the number of ATOMS in such a molar quantity. And because there are 4 moles of atoms in EACH mole of ammonia, we get a mole of atoms as our final answer....

... $0.75 \times {N}_{A}$ $\text{hydrogen atoms}$ $+$ $0.25 \times {N}_{A}$ $\text{nitrogen atoms}$.

i.e. a mole of atoms in TOTAL.