Question

Mass of hydrogen atom in 43g of hexane ${{C}_{6}}{{H}_{14}}$ is:
a.) 14g
b.) 10g
c.) 7g
d.) 6g

Answer 1

Mass of hydrogen atom can be calculated by number of moles and mole concept. Atomic mass of carbon is 12 and atomic mass of hydrogen is 1. Moles can be calculated by dividing given mass to molar mass. Molar mass of hexane is 86.

Complete step by step answer:
-Molar mass of hexane can be calculated as follows:
Atomic mass of carbon is 12 and atomic mass of hydrogen is 1 so molar mass of hexane can be calculated as
= 6 (atomic mass of carbon) + 14 (atomic mass of hydrogen)
=6 (12) + 14 (1)
=72 +14
=86

As we know one mole is equal to molar mass, so one mole of hexane is 86g.
Number of moles of hexane can be obtained by taking the ratio of given mass to molar mass.
=$\dfrac{43}{86}$g = 0.5 moles
So 43 g of hexane is equal to 0.5 moles.

In 1 mole of hexane, there are 14 hydrogen atoms and an atomic mass of 14 hydrogen atoms is equal to 14.
Hence, 0.5 mole of hexane, mass of hydrogen is = 0.5 (14) =7g
Mass of the hydrogen atom in 43g of hexane ${{C}_{6}}{{H}_{14}}$ is So, the correct answer is “Option C”.

Note: Number of moles can be obtained by taking ratio of given mass to molar mass and then mass of hydrogen atoms can be calculated by multiplying number of moles and mass of all hydrogen atoms present in molecule. 1 mole is equal to molecular mass or molar mass.