Question

The mass percent of calcium, phosphorus and oxygen in calcium phosphate, $C{a}_3{\left(P{O}_4\right)}_2$ is :

• A. $Ca=38.71\%$, $P=20.0\%$, $O=41.29\%$
• B. $Ca=20.0\%$, $P=38.71\%$, $O=41.29\%$
• C. $Ca=38.71\%$, $P=41.29\%$, $O=20.0\%$
• D. $Ca=41.29\%$, $P=20.0\%$, $O=38.71\%$

Answer 1

Answer: (A)

$Ca=38.71\%$, $P=20.0\%$, $O=41.29\%$

Molecular formula of calcium phosphate is $C{a}_3{\left(P{O}_4\right)}_2$.
Its molar mass is $3\left(40\right)+2\left(31\right)+8\left(16\right)=310$ g/mol.
Percent of calcium $=\frac{120}{310}\times 100=38.71\%$
Percent of phosphorus $=\frac{62}{310}\times 100=20.0\%$
Percent of oxygen $=\frac{128}{310}\times 100=41.29\%$