Question

How can I calculate the percentage by mass of sodium in sodium azide, $Na{{N}_{3}}$(s); used in automobiles air bags?

Answer 1

Hint: First of all, you should know about the atomic mass of sodium and the atomic mass of the sodium azide and then, by them you can easily find the percentage of the sodium in the sodium azide by applying the formula as: $Percentage=\dfrac{mass\text{ }of\text{ that element in the compound}}{mass\text{ }of\text{ the compound}}\times 100$. Now answer the given statement.

Complete step by step answer:
- Sodium azide is an inorganic compound which consists of two elements i.e. sodium and the nitrogen elements. It is colorless in nature and is mostly used as the gas forming airbags in automobiles and is also used in the preparation of other azide compounds too.
- Now considering the statement;
We can easily calculate the percentage of the sodium in sodium azide by using the formula as;
$Percentage=\dfrac{mass\text{ }of\text{ }Na}{mass\text{ }of\text{ }Na{{N}_{3}}}\times 100$ --------------------(1)
So, we know that the atomic mass of the sodium atom=23
And molar mass of sodium azide i.e. $Na{{N}_{3}}$is = $23 + 3\times 14 = 65\text{ }g\text{ mol}{{\text{e}}^{-1}}$
Now put these two values in equation (1), the percentage of the sodium in the sodium azide comes out to be:
$\begin{align}
 & Percentage=\dfrac{23}{65}\times 100 \\
 & \text{ =35}\text{.38 }\%\text{ } \\
\end{align}$
Thus, in this way, we can calculate the percentage by mass of sodium in sodium azide, $Na{{N}_{3}}$(s) which is used in automobiles air bags.

Note: By knowing the percentage composition of each element in the compound, we can check whether the given sample contains the same percentage of elements as is present in the pure compound. In other words, we can say that we can check the purity of a given sample by analyzing this data.