WBCS.LIVE practice question

If number of molecules present in 9g of water is n, then number of molecules present in 44g of carbon-di-oxide is:

Solve this multiple-choice question and check the correct answer with its explanation below.

Answer options

  1. n
  2. 2n
  3. n/2
  4. 3n

Correct answer and explanation

Correct answer: 3n

Explanation: If 9 g of water has n molecules, then 44 g of CO₂ has 3n molecules. 📚 Other Information: ▪️ Molar mass of H₂O = 18 g → 9 g water = 0.5 mol. ▪️ 1 mol = 6.022 × 10²³ molecules → 0.5 mol = n molecules. ▪️ Molar mass of CO₂ = 44 g → 44 g = 1 mol = 6.022 × 10²³ molecules. ▪️ Ratio = 1 mol CO₂ ÷ 0.5 mol H₂O = 2/0.5 = 3. ▪️ Therefore, CO₂ molecules = 3n. ▪️ Demonstrates Avogadro’s Law (equal moles contain equal molecules). ▪️ Molecular comparison often used in stoichiometry. ▪️ Useful in chemical equation balancing.