Question

Ratio of number of oxygen atoms in $Ca_3(PO_4)_2$ and $H_3PO_3$, if both contain same number of $P$ atoms, is

• A. $3 : 4$
• B. $4 : 3$
• C. $2 : 3$
• D. $3 : 2$

Answer 1

Answer: (B)

$4 : 3$

Answer 2

$1$ molecule of $Ca_3(PO_4)_2$ contains $2$ atoms, of $P$ and $1$ molecule of $H_3PO_3$ contains $1$ atom of $P$. So, $0.5$ molecule of $Ca_3(PO_4)_2$ and $1$ molecule of $H_3PO_3$ contain equal number of $P$ atoms. Number of oxygen atoms in $0.5$ molecule of $Ca_3(PO_4)_2 = 0.5 \times 8 = 4$ And in $1$ molecule $H_3PO_3 = 3$