Question

The number of water molecules is maximum in :

• A. 18 gram of water
• B. 18 moles of water
• C. 18 molecules of water
• D. 1.8 gram of water

Answer 1

The Correct Option is B

To determine which option has the maximum number of water molecules, we must understand the relationship between moles, grams, and molecules in chemistry. 

The key concept here is Avogadro's number, which tells us that 1 mole of any substance contains \(6.022 \times 10^{23}\) molecules of that substance.

1. Let's break down each option:
   • 18 grams of water:

Since the molar mass of water (H₂O) is 18 g/mol, 18 grams of water is equivalent to 1 mole of water. Hence, it contains \(6.022 \times 10^{23}\) water molecules.

• 18 moles of water:

This represents 18 times the number of molecules in 1 mole. Therefore, it contains \(18 \times 6.022 \times 10^{23}\) water molecules.

• 18 molecules of water:

This is just 18 individual molecules of water, which is significantly fewer than the number in a mole or gram.

• 1.8 grams of water:

Given the molar mass, 1.8 grams is \(\frac{1.8}{18} = 0.1\) moles, meaning it contains \(0.1 \times 6.022 \times 10^{23}\) molecules.

1. Comparison:

The number of water molecules is highest in 18 moles of water because it contains \(18 \times 6.022 \times 10^{23}\) molecules, which is far more than in any other option.

Therefore, the correct answer is 18 moles of water.