Question

In which compound is the percent compositionby mass of chlorine equal to 42%?

Answer 1

The answer is (3) HClO3. The percent composition mass of chlorine is equals to the mass of one Cl atom /gram-formula mass of the compound. So after calculation, we can get the right answer.

Answer 2

Answer The correct option is, (3) $HClO_3$ (gram-formula mass = 84 g/mol)

Explanation : Given,

Molar mass of chlorine = 35.5 g/mole

Formula used :

$\% \text{ Composition by mass of chlorine}=\frac{\text{Mass of chlorine}}{\text{Mass of given chlorine compound}}\times 100$

Now we have to calculate the percent composition by mass of chlorine.

For option 1 :

$\% \text{ Composition by mass of chlorine}=\frac{35.5g/mole}{52g/mole}\times 100=68.2\%$

For option 2 :

$\% \text{ Composition by mass of chlorine}=\frac{35.5g/mole}{68g/mole}\times 100=52.2\%$

For option 3 :

$\% \text{ Composition by mass of chlorine}=\frac{35.5g/mole}{84g/mole}\times 100=42.2\%$

For option 4 :

$\% \text{ Composition by mass of chlorine}=\frac{35.5g/mole}{100g/mole}\times 100=35.5\%$

From this we conclude that the $HCLO_3$ is the compound in which the percent composition by mass of chlorine equal to 42%.

Hence, the correct option is, (3)