Question

The percentage of nitrogen in aluminium nitride is:
[Al = 27, N = 14]
A. 34.15%
B. 14.15 %
C. 24.30 %
D. 38.15 %

Answer 1

Hint: The mass percentage composition of the element tells about the contribution made by a single element to the total molecular weight. The mass percentage composition is calculated by dividing the atomic weight of the element by the molecular weight multiplied by 100.

Complete step by step answer:
Given,
The atomic weight of aluminium is 27g/mol.
The atomic weight of nitrogen is 14 g/mol.
The mass percent composition of each element present in the molecule shows the amount of each element contributed to the total molar mass. The contribution made by each element is expressed as the percentage in whole.
The mass percentage composition of element is calculated by the formula as shown below.
$mass\;percentage = \dfrac{{atomic\;weight}}{{Total\;molecular\;weight}} \times 100$……..(i)
The calculation of the mass percentage of nitrogen in aluminium nitride is done as shown below.
Step 1: Find the atomic weight of the element present in the molecule aluminium nitride.
The atomic weight of nitrogen is 14 g/mol.
The atomic weight of aluminium is 27 g/mol.
Step 2: Find the total molecular weight of the molecule aluminium nitride.
The molecular weight is calculated by adding the atomic weight of the individual element and multiplying the number of elements with the atomic number.
The chemical formula of aluminium nitride is AlN.
Molecular weight = $27 + 14$
$\Rightarrow$Molecular weight = 41 g/mol
Step 3: Find the mass percent composition of nitrogen.
To calculate the mass percent composition of nitrogen, substitute the values in equation (i).
$\Rightarrow mass\;percentage = \dfrac{{14}}{{41}} \times 100$
$\Rightarrow mass\;percentage = 34.15\%$
Thus, the mass percentage of nitrogen in aluminium nitride is 34.15%.
Therefore, the correct option is A.

Note: The formula of mass percentage composition of elements is different from the mass percentage formula used to calculate for solute, where the mass of solute is divided by the total mass of the solution multiplied by 100.