Question

A sample of ethane has the same mass as 10.0 million molecules of methane.
calculateHow many C2H6 molecules does the sample contain?

Answer 1

Given,

Mass of given sample of C2H6(ethane) = mass of 107 CH4 molecules

= 16 × 107/Avogadro. constant

No. of C2H6 molecules present.

= Mass / 30 × Avogadro constant.

= (16 × 107/ Avogadro. constant × 30) × Avogadro. constant

= 5.34 × 106.

Answer 2

Answer:

Molar mass of methane = 16 g/mol

1 mole of methane contains = 6.023 x 1023 molecules

Mass of 6.023 x 1023 molecules of methane = 16 g

Mass of 1 molecule of methane = 16/ (6.023 x 1023 ) g

Mass of 10 million molecules or 10 x 106 molecules = [16/ (6.023 x 1023 ) ] x 107 = 2.65 x 10-16 g

Thus mass of ethane sample = 2.65 x 10-16 g

Molar mass of ethane or mass of 1 mole of ethane = 30 g/mol

If 30 g of ethane contain = 6.023 x 1023 molecules

Then ,

2.65 x 10-16 g of ethane contains = [6.023 x 1023 /30] x 2.65 x 10-16 = 5.3203 x 106 molecules of ethane

Hope it Helps !!!!