Science ·Class 9 Science

Calculate the molecular mass of water (HaO). Class 9

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· Jul 06, 2026 · Reviewed & updated Sep 17, 2026 · 1 min read

Question 1.

Answer:

Atomic mass of hydrogen = 1u, oxygen = 16 u

Water has two atoms of hydrogen and one atom of oxygen.

Molecular mass of water = 2 (atomic mass of H) + atomic mass of O

= (2 × 1) + (1 × 16) = 18 u

Question 2.

Calculate the molecular mass of carbon dioxide (CO₂). Class 9

Answer:

Atomic mass of carbon = 12 u, oxygen = 16 u

Carbon dioxide has one atom of carbon and two atoms of oxygen.

Molecular mass of carbon dioxide = (atomic mass of C) + 2 (atomic mass of O)

= (1 × 12) + (2 × 16) = 44 u