Question

Calculate the mass percent of different elements present in sodium sulphate $N{a_2}S{O_4}$.

Answer 1

This question gives the knowledge about the molecular or molar mass and molecular formula. The molecular formula is the representation of chemical compounds. It comprises the chemical symbols for the elements tailed by the numeric subscripts labelling the atoms of each element present in a molecule.

Formula used:
The formula used to determine the mass percentage is as follows:
$M\% = \dfrac{m}{M} \times 100$
Where $m$ is the mass of the element, $M$ is molar mass, and $M\%$ is the mass percentage.

Complete step by step answer:
The molecular formula is the representation of chemical compounds. It comprises the chemical symbols for the elements tailed by the numeric subscripts labelling the atoms of each element present in a molecule.
The given compound is sodium sulphate $N{a_2}S{O_4}$
Now, calculate its molar mass by substituting the mass of individual elements $Na$ as $23$, $S$ as $32$ and $O$ as $16$ as follows:
$\Rightarrow \left[ {\left( {2 \times 23} \right) + 32 + \left( {4 \times 16} \right)} \right]$
On simplifying, we get
$\Rightarrow 142g$
Therefore, the molecular mass of $N{a_2}S{O_4}$ is $142g$.
Now, we will determine the mass percentage of each element as follows:
To calculate the mass percentage of sodium element in the given compound we have,
$M\% = \dfrac{{46}}{{142}} \times 100$
On simplifying, we get
$M\% = 32.3$
Therefore, the mass percentage sodium element is $32.3\%$ .
To calculate the mass percentage sulphur element we have,
$M\% = \dfrac{{32}}{{142}} \times 100$
On simplifying, we get
$M\% = 22.5$
Therefore, the mass percentage sulphur element is $22.5\%$ .
To calculate the mass percentage oxygen element we have,
$M\% = \dfrac{{64}}{{142}} \times 100$
On simplifying, we get
$M\% = 45.05$

Therefore, the mass percentage oxygen element is $45.05\%$ .

Note: You should always remember the molecular weights of chemical compounds. Mass percent determines the percentage of amount of a substance present in the particular compound by examining the ratio of given amount of a particular element to the total given amount of chemical compound.