Verified Answer :

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 : 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 %

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