Question

What mass of hydrogen is in a 102.0 g quantity of methane (CH4)?

A. 1.01 g H
B. 2.57 g H
C. 4.0 g H
D. 25.7 g H

Answer 1

Methane formula is CH₄. Molar mass of methane is calculated as taking the sum of molar masses of the elements multiplied by the number of atoms of the element making up the compound.
Molar mass - (molar mass of C) + (molar mass of H x 4)
= 12.01 + (1.007x4) = 16.04 g/mol
round it off to 16 g/mol
In 16 g of methane, 4.03 g of H is present
In 1 g of methane , 4.03/16 g of H
Therefore in 102 g of methane - 4.028/16 x 102 g = 25.7 g of H is present
Correct answer is D.