Which one of the following statements is NOT correct?

CONCEPT:

Avogadro's Law and Molar Relationships at STP

• Avogadro's Law: At Standard Temperature and Pressure (STP), 1 mole of any ideal gas occupies 22.4 liters of volume.
• Molecular Relationships:
  • 1 mole of a substance contains Avogadro's number of molecules, which is 6.022 × 10²³.
  • 1 mole of a compound is equivalent to its molar mass in grams.

EXPLANATION:

• Half mole of nitrogen gas is measured 11.2 liters at STP.
  • At STP, 1 mole of nitrogen gas occupies 22.4 liters.
  • Thus, half a mole of nitrogen gas will occupy 22.4 ÷ 2 = 11.2 liters.
  • This statement is correct.
• 17 grams of ammonia gas contains 6.022 × 10²³ molecules at STP.
  • The molar mass of ammonia (NH₃) is 14 (N) + 1×3 (H) = 17 g/mol.
  • 17 grams of ammonia corresponds to 1 mole, which contains 6.022 × 10²³ molecules.
  • This statement is correct.
• 22.4 liters of CO₂ gas at STP contains 44 grams of molecules.
  • The molar mass of CO₂ is 12 (C) + 16×2 (O) = 44 g/mol.
  • At STP, 22.4 liters of CO₂ corresponds to 1 mole, which weighs 44 grams.
  • This statement is correct.
• 4 grams of hydrogen gas contains 6.022 × 10²³ molecules.
  • The molar mass of H₂ is 1×2 = 2 g/mol.
  • 4 grams of H₂ corresponds to 4 ÷ 2 = 2 moles.
  • Since 1 mole contains 6.022 × 10²³ molecules, 2 moles would contain 2 × 6.022 × 10²³ = 1.2044 × 10²⁴ molecules.

The given statement is incorrect because 4 grams of H₂ does not contain 6.022 × 10²³ molecules, but rather twice that amount.

Therefore, the incorrect statement is Option 4.