Question

Question 12 (5 points)

Answer 1

Answer : The correct option is, (A) 82.35% N; 17.65% H

Explanation :

Percent composition : It is calculated by dividing the mass of each element in one mole of the compound that means dividing the mass of each element by the total molar mass of the compound.

Formula used :

$\%\text{ Composition}=\frac{\text{Mass of each element}}{\text{Molar mass of compound}}\times 100$

The given molecule is, $NH_3$

Molar mass of H = 1 g/mole

Molar mass of N = 14 g/mole

First we have to calculate the molar mass of $NH_3$ .

Molar mass of glucose $NH_3$ = $1(14)+3(1)=17g/mole$

Now we have to calculate the percent composition of nitrogen and hydrogen in $NH_3$.  

As we now that there are 1 number of nitrogen atom and 3 number of hydrogen atoms.

$\%\text{ Composition of nitrogen}=\frac{\text{Mass of nitrogen}}{\text{Molar mass of }NH_3}\times 100$

Now put all the given values in this formula, we get:

$\%\text{ Composition of nitrogen}=\frac{14}{17}\times 100=82.35\%$

and,

$\%\text{ Composition of hydrogen}=\frac{\text{Mass of hydrogen}}{\text{Molar mass of }NH_3}\times 100$

Now put all the given values in this formula, we get:

$\%\text{ Composition of hydrogen}=\frac{3\times 1}{17}\times 100=17.65\%$

Therefore, the percent composition of nitrogen and hydrogen in $NH_3$ is, 82.35 % and 17.65 % respectively.

Answer 2

The correct answer would be B. 80.55% N; 19.45% H