Question

What is the percent by mass of hydrogen in $HF$?

• A. $2$
• B. $20$
• C. $1$
• D. $5$

Answer 1

The correct option is D $5$

$\%$ by mass is defined as ratio of mass of elements to the total mass of compound.

$\Rightarrow \%$ by mass of hydrogen $=\frac{1}{1+19}\times 100=\frac{1}{20}\times 100=5\%$