Question

Calculate the molecular masses of the following compounds:
A.Methane, $C{{H}_{4}}$
B.Ethane, ${{C}_{2}}{{H}_{6}}$
C.Ethene, ${{C}_{2}}{{H}_{4}}$
D.Ethyne, ${{C}_{2}}{{H}_{2}}$
(Atomic masses: C = 12u, H = 1u)

Answer 1

Hint: The molar mass or molecular mass of a compound can be calculated by adding the standard atomic masses of the constituent atoms. Atomic mass is a unit described as the masses of the individual atoms and molecules. Using this information, we can solve the given question.

Complete answer:
- The molecular mass (m) is the mass of a given molecule. It is measured in Daltons (Da or u).
- For the question, molecular mass can be calculated using the following formula:
Molecular mass = (no. of atoms x atomic mass of C) + (no. of atoms x atomic mass of H)
-We have, Atomic mass of C = 12u and atomic mass of H = 1u
A.Methane, $C{{H}_{4}}$
Using the above stated formula, substituting the given value, we get
Molecular Mass = (1 x 12) + (4 x 1)
Molecular Mass = 12 + 4
Molecular Mass = 16u

B.Ethane, ${{C}_{2}}{{H}_{6}}$
Using the above stated formula, substituting the given value, we get
Molecular Mass = (2 x 12) + (6 x 1)
Molecular Mass = 24 + 6
Molecular Mass = 30u

C.Ethene, ${{C}_{2}}{{H}_{4}}$
Using the above stated formula, substituting the given value, we get
Molecular Mass = (2 x 12) + (4 x 1)
Molecular Mass = 24 + 4
Molecular Mass = 28u

D.Ethyne, ${{C}_{2}}{{H}_{2}}$
Using the above stated formula, substituting the given value, we get
Molecular Mass = (2 x 12) + (2 x 1)
Molecular Mass = 24 + 2
Molecular Mass = 26u

Note:
Different molecules of the same compound may have different molecular masses because they contain different isotopes of an element. It is the sum of the atomic masses of all atoms in a molecule.