Question

Which one of the following contains 52% carbon by mass? Possible Answers

a)C2H2

b)CH4

c)CH3CH2OH

d)CO2

Answer 1

I have calculates the mass percentage for all the options.

For none of them mass percentage is 50 %

a)

Molar mass of C2H2,
MM = 2*MM(C) + 2*MM(H)
= 2*12.01 + 2*1.008
= 26.036 g/mol


MM of C2H2 = 26.036
Lets calculate the mass of element

mass of C = 2*MM(C)
= 24.02 g

Mass % of C = (24.02*100)/26.036
= 92.256875

b)
Molar mass of CH4,
MM = 1*MM(C) + 4*MM(H)
= 1*12.01 + 4*1.008
= 16.042 g/mol


MM of CH4 = 16.042
Lets calculate the mass of element

mass of C = 1*MM(C)
= 12.01 g

Mass % of C = (12.01*100)/16.042
= 74.865977

c)
Molar mass of CH3COOH,
MM = 2*MM(C) + 4*MM(H) + 2*MM(O)
= 2*12.01 + 4*1.008 + 2*16.0
= 60.052 g/mol


MM of CH3COOH = 60.052
Lets calculate the mass of element

mass of C = 2*MM(C)
= 24.02 g

Mass % of C = (24.02*100)/60.052
= 39.998668

d)
Molar mass of CO2,
MM = 1*MM(C) + 2*MM(O)
= 1*12.01 + 2*16.0
= 44.01 g/mol


MM of CO2 = 44.01
Lets calculate the mass of element

mass of C = 1*MM(C)
= 12.01 g

Mass % of C = (12.01*100)/44.01
= 27.289252