Question

116 g of a substance upon dissociation reaction, yields 7.5 g of hydrogen, 60 g of oxygen and 48.5 g of carbon. Given that the atomic masses of H, O and C are 1, 16 and 12 respectively. The data agrees with how many formulae of the following?

Options

• CH₃COOH

• HCHO

• CH₃OOCH₃

• CH₃CHO

Answer 1

HCHO

Explanation:

Element	% of Mass	% of Moles	Relative moles
H	`7.5/116 xx 100` = 6.46	`6.46/1` = 6.46	2
O	`60/116 xx 100` = 51.72	`51.72/16` = 3.23	1
C	`48.5/116 xx 100` = 41.81	`41.81/12` = 3.48	1

∴ Empirical formula = COH₂

The empirical formula goes with acetic acid CH₃COOH and formaldehyde HCHO.

This data agrees with the 2 formulae.