Naphthalene ball contains $93.71 %$ carbon and $6.29 %$ hydrogen. If its molar mass is $128$ g $m o l^{- 1}$ , calculate its molecular formula.

Open in App

Solution

Mass of carbon $= 93.71$
Mass of hydrogen $= 6.29$
Number of mole (carbon) $= \frac{93.71}{12} = 7.8$
Number of mole (hydrogen) $= \frac{6.29}{1} = 6.29$

Hence most simple ratio, for carbon $\frac{7.8}{6.29} = 1.25$
for hydrogen, $\frac{6.29}{6.29} = 1$

since, it is not a whole number we multiply the ratio by $5$ to get a whole number ratio.

Lowest whole number ratio is
for carbon $= 5$
for hydrogen $= 4$
Empirical formula $= C_{5} H_{4}$
Ratio $= \frac{128 g}{64 g} = 2$
molecular formula $\begin{matrix} = 2 \times C_{5} H_{4} = C_{10} H_{8} \end{matrix}$

Suggest Corrections

Similar questions

A compound 4.07% hydrogen, 24.27% carbon and 71.65% chlorine. Its molar mass is 98.96 g. What are its emperical formula and molecular formula?

4.07

24.27

71.6

98.96 g {m o l}^{- 1}

A compound contains 4.07% hydrogen, 24.27% Carbon and 71.65% Chlorine. Its molar mass is 90.96g. What are it's empirical and molecular formula?

18.6 %

1.55 %

55.04 %

129

Join BYJU'S Learning Program