Question

An organic compound has a molar mass of 168.2 g/mol and contains 8.32% hydrogen atoms by mass. How many hydrogen atoms are in each molecule of this compund?

Answer 1

As per the definition of percent composition, 100 g of the organic compound contains 8.32 g hydrogen. Therefore,

168.2 g of the compound contains (168.2 g)*(8.32 g/100 g) = 13.99424 g hydrogen.

We know that 1 mole of the compound weighs 168.2 g; therefore, 1 mole of the organic compound contains 13.99424 g hydrogen.

The atomic mass of hydrogen is 1.008 g; therefore,

13.99424 g hydrogen = (13.99424 g)*(1 atom/1.008 g) = 13.8832 atoms ≈ 14 atoms (the number of atoms can only be positive integral values).

The given organic compound contains 14 atoms of hydrogen (ans).