Question

`0.2 g` of organic compound containing carbon, hydrogen and oxygen on combustion yielded `0.147 g CO_(2)` and `0.12 g` water. What will be the content of oxygen in the substance?
A. `78.45%`
B. `73.295%`
C. `83.23%`
D. `89.50%`

Answer 1

Correct Answer - B
It is usual to determine the percentage to oxygen by subtracting the percentage of all the other elements from one hundred.
`% C = (12)/(44) xx (m_(CO_(2)))/(m_(o .c.)) xx 100% = (12)/(44) xx (0.147 g )/(0.2 g) xx 100% = 20%`
`% H = (2)/(18) xx (m_(H_(2)O))/(m_(o .c.)) xx 100% = (2)/(18) xx (0.12 g)/(0.2 g) xx 100% = 6.66%`
Thus, , `% O = (100%) - (% C + % H)`
`= (100%) - (20% + 6.66%)`
`= 73.34%`