Question

In an ionic compound moles ratio of cation to anion is $1:2$. If atomic masses of metal and non-metal respectively are $138$ and $19$, then correct statement is

• A. molecular mass of compound is $176$
• B. formula mass of compound is $176$
• C. formula mass of compound is $157$
• D. molecular mass of compound is $157$

Answer 1

Answer: (B)

Metal $\Rightarrow$ Cation $\to A\left(138\right)$
Non-metal$\Rightarrow$ Anion $\Rightarrow B\left(19\right)$
Ionic compound$=A{B}_2$
$\therefore$ Formula mass (G.M.M. for ionic compound)
$=138+2\times 19=176$