Question

What is the percent by mass of oxygen in propanal, CH3CH2CHO?(1) 10.0% (3) 38.1%

Answer 1

17.6% oxygen
% mass = molar mass of part over molar mass of whole,
molar mass of oxygen is 16
molar mass of carbon is 12
molar mass of hydrogen is 1
so (16) / (16+12*6+3) = 16/91 = 17.58%

Answer 2

Answer : The percent by mass of oxygen in propanal is, 27.58 %

Solution : Given,

Molar mass of carbon = 12 g/mole

Molar mass of hydrogen = 1 g/mole

Molar mass of oxygen = 16 g/mole

First we have to calculate the molar mass of propanal, $CH_3CH_2CHO$

Molar mass of propanal, $CH_3CH_2CHO$ = $3(12)+6(1)+16=58g/mole$

Now we have to calculate the percent by mass of oxygen in propanal.

$\text{Percent by mass of oxygen}=\frac{\text{Mass of oxygen}}{\text{Mass of propanal}}\times 100=\frac{16}{58}\times 100=27.58\%$

Therefore, the percent by mass of oxygen in propanal is, 27.58 %