Question

Find the molecular mass of
(a) H2O
(b) HNO3
​

Answer 1

Answer:

(a) The molecular mass of water is:-

   relative mass of hydrogen=1u

   relative mass of oxygen=16u 

   ∴ (2 × Atomic mass of hydrogen) + (1 × Atomic mass of oxygen)

⇒ [2(1.0084) + 1(16.00 u)]

⇒ 2.016 u + 16.00 u

⇒18.016

⇒ 18.02 u

(b) molecular mass of hno3 is:-

   hydrogen=1u

   nitrogen=14u

    oxygen=16u

    ∴(1 × Atomic mass of hydrogen) + (1 × Atomic mass of oxygen)+(3 × Atomic mass of oxygen)

⇒1+14+48

=63g/mol

Explanation:

Hope it helps!

Answer 2

Explanation:

The average mass of one H2O molecule is 18.02 amu. The number of atoms is an exact number, the number of mole is an exact number; they do not affect the number of significant figures. The average mass of one mole of H2O is 18.02 grams. This is stated: the molar mass of water is 18.02 g/mol.

The molar mass of the chemical substance is equal to the sum of the atomic mass of the individual atoms. (1 × 1) +(1 × 14) + (16×3) = 63 u.