Assertion: 18 g of water contains one mole of water molecules. Reason: The molar mass of water is 18 g mol⁻¹.

📘 Assertion–Reason Analysis

🔵 Assertion

18 g of water contains one mole of water molecules.

This statement is True. The number of moles is calculated using:

Number of moles = Mass ÷ Molar Mass

For water, the mass is 18 g and its molar mass is 18 g mol⁻¹.

🟠 Reason

The molar mass of water is 18 g mol⁻¹.

This statement is also True. The molecular formula of water is H₂O.

Molar Mass of H₂O

= (2 × 1) + (1 × 16)

= 2 + 16

= 18 g mol⁻¹

🧮 Step-by-Step Calculation

n = Mass ÷ Molar Mass

n = 18 ÷ 18

n = 1 mol

Therefore, 18 g of water contains exactly one mole of H₂O molecules.

🎬 H₂O Molecule Animation

H H O → 1 mol H₂O

18 g H₂O = 1 mol H₂O

One mole of H₂O contains 6.022 × 10²³ water molecules.

🔗 Conceptual Relationship

18 g H₂O → 1 mol H₂O → 6.022 × 10²³ molecules

The Reason gives the molar mass needed to establish the Assertion.

✅ Final Answer

Both Assertion and Reason are TRUE, and Reason is the correct explanation of Assertion.

🎯 Key Concept

Molar Mass of H₂O = 18 g mol⁻¹

18 g H₂O = 1 mol H₂O

1 mol H₂O = 6.022 × 10²³ molecules