Calculate the molar mass of the following substances.

• A. Ethylene, C₂H₂
• B. Sulphur molecule, S₈
• C. Phosphorus molecule, P₄ (Atomic mass of phosphorus = 31)
• D. Hydrochloric acid, HCl
• E. Nitric acid, HNO₃

To find the molar mass of each substance, we need to sum the atomic masses of all the atoms in the molecule. Here’s how to calculate the molar mass for each of the given substances:

A. Ethylene (C₂H₂)

Ethylene consists of 2 carbon (C) atoms and 2 hydrogen (H) atoms.

• Carbon: 2 × 12.01 g/mol = 24.02 g/mol
• Hydrogen: 2 × 1.008 g/mol = 2.016 g/mol

Total Molar Mass: 24.02 g/mol + 2.016 g/mol = 26.036 g/mol

B. Sulphur Molecule (S₈)

The sulphur molecule contains 8 sulfur (S) atoms.

• Sulfur: 8 × 32.07 g/mol = 256.56 g/mol

Total Molar Mass: 256.56 g/mol

C. Phosphorus Molecule (P₄)

Phosphorus consists of 4 phosphorus (P) atoms.

• Phosphorus: 4 × 31 g/mol = 124 g/mol

Total Molar Mass: 124 g/mol

D. Hydrochloric Acid (HCl)

Hydrochloric acid is made up of 1 hydrogen (H) atom and 1 chlorine (Cl) atom.

• Hydrogen: 1 × 1.008 g/mol = 1.008 g/mol
• Chlorine: 1 × 35.45 g/mol = 35.45 g/mol

Total Molar Mass: 1.008 g/mol + 35.45 g/mol = 36.458 g/mol

E. Nitric Acid (HNO₃)

Nitric acid consists of 1 hydrogen (H) atom, 1 nitrogen (N) atom, and 3 oxygen (O) atoms.

• Hydrogen: 1 × 1.008 g/mol = 1.008 g/mol
• Nitrogen: 1 × 14.01 g/mol = 14.01 g/mol
• Oxygen: 3 × 16.00 g/mol = 48.00 g/mol

Total Molar Mass: 1.008 g/mol + 14.01 g/mol + 48.00 g/mol = 63.018 g/mol

In summary, the molar masses are:

• Ethylene: 26.036 g/mol
• Sulphur (S₈): 256.56 g/mol
• Phosphorus (P₄): 124 g/mol
• Hydrochloric Acid (HCl): 36.458 g/mol
• Nitric Acid (HNO₃): 63.018 g/mol