Question

Which compound has the highest molar mass

Answer 1

Answer: Option (a) is the correct answer.

Explanation:

Molar mass of a substance means the sum of atomic masses of all the atoms present in a substance.

A polyethylene molecule is made up of "n" number of repeated units ethylene. Hence, it will have highest molar mass because there are more number of atoms present in a polyethylene molecule.

Whereas an ethane molecule is $C_{2}H_{6}$ and its molar mass is $[(12 \times 2) + (1 \times 6)]g/mol$ = 30 g/mol

An octane molecule is $C_{8}H_{18}$ and its molar mass is $[(12 \times 8) + (1 \times 18)]g/mol$ = 114 g/mol

An octanal molecule is $C_{8}H_{16}O$ and its molar mass is $[(12 \times 8) + (1 \times 16) + 16]g/mol$ = 128 g/mol

Thus, we can conclude that polyethylene, a polymer of ethane has the highest molar mass.

Answer 2

First you must know the structure.
polyethlyene is the repeated C2H4 (ethene)
ethane is C2H6 = 30
octane is C8H18 = 114
octanal is C8H16O = 128
octanal has the highest.
molar mass refer to periodic table. where C=12 H=1 O=16