A hydrocarbon (an organic compound containing only C and H) is found to be 7.74% H. If the molecular weight is known to be between 70 and 85 u, find the molecular formula.

Question

Chemistry

Cisco

14 May, 20:42

A hydrocarbon (an organic compound containing only C and H) is found to be 7.74% H. If the molecular weight is known to be between 70 and 85 u, find the molecular formula.

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Jacob Garrett · Answer 1

The molecular weight is between 70 and 85. Let's accidentally pick some quantity in amid, like 78.

7.74% of 78 is how many 'u' there are of H:

78 u * 7.74% = 78 u *.0774 = 6.0372 u

The only hydrocarbon below that has 6 hydrogens is C6H6. We can even check this answer:

Total u = 6C + 6H

= 6 (12.01) + 6 (1.0079)

= 78.11 u

6 (1.0079) / 78.11 * 100 = 7.74%