Question

Calculate the percentage composition of calcium nitrate.

Answer 1

Hint: The ratio of amount of each element present in a compound, to total amount of individual elements present in the compound multiplied by 100 is called the percentage composition of that particular element.

Complete step by step solution:
The formula of Calcium nitrate is \[{\text{Ca(N}}{{\text{O}}_3}{)_2}\].
So, total molecular mass of the compound is given as = \[{\text{Atomic mass Ca + (Atomic mass of N + Atomic mass of}}{{\text{O}}_{\text{3}}}{\text{)}} \times {\text{ 2}}\]
\[ = {\text{ 40 + [ 2}} \times 7{\text{ + 16}} \times {\text{6] }}\]
The formula of Calcium nitrate is \[{\text{Ca(N}}{{\text{O}}_3}{)_2}\] \[{\text{ = 150}}\]
The formula to calculate percentage composition of individual element is
\[{{\% X = }}\dfrac{{{\text{Mass of X}}}}{{{\text{Total molecular mass of compound}}}}{{ \times 100}}\]
So, we calculate the % of Ca as-
\[{{\% Ca = }}\dfrac{{{\text{Mass of Ca}}}}{{{\text{Total molecular mass of compound}}}}{{ \times 100}}\]
\[{{\% Ca = }}\dfrac{{40}}{{150}}{{ \times 100}}\] \[{\text{ = 26}}{\text{.6}}\]
For Nitrogen, \[{{\% N = }}\dfrac{{14}}{{150}}{{ \times 100 = 9}}{\text{.33}}\]
For Oxygen, \[{{\% O = }}\dfrac{{96}}{{150}}{{ \times 100 = 64}}\]
So, in Calcium nitrate - Calcium is 26.6%, Nitrogen is 9.33% and Oxygen is 64%.

Additional Information:
Norges Saltpeter is another name for Calcium nitrate. It is nitrate salt and was synthesized by the Birkeland–Eyde process. It is usually found in tetrahydrate form i.e. \[{\text{Ca(N}}{{\text{O}}_3}{)_2}.{\text{4}}{{\text{H}}_2}{\text{O}}\] and is granular solid which highly absorbs moisture from air. It is widely used as an oxidising agent and as a fertilizer in agriculture. Calcium nitrate is also useful in making explosives and fireworks. Apart from these applications, it is also used as a starting compound in manufacturing of other types of nitrates.

Note: Percentage composition of a compound is useful in chemical analysis. It is also used in determining the empirical formula of the compound in organic chemistry. If molecular weight and percentage composition is known, we can find the mole: mole ratio of all elements in a compound.