The volume occupied by 17g of H2S at s.t.p. is [H = 1.00, S = 32.0, Molar volume = 22.4 dm3]

Analyze the question: We need the volume of 17 g of hydrogen sulphide (H₂S) gas at s.t.p. This is a mole-to-volume conversion.

Concept:

• Number of moles = mass ÷ molar mass
• At s.t.p., 1 mole of any gas occupies 22.4 dm³
• Volume = moles × 22.4 dm³

Solution:

Step 1: Molar mass of H₂S = (2 × 1.00) + 32.0 = 34.0 g/mol

Step 2: Moles of H₂S = 17 ÷ 34.0 = 0.5 mol

Step 3: Volume at s.t.p. = 0.5 × 22.4 = 11.2 dm³

Answer: The volume is 11.2 dm³, which is option A.

Tip: Notice that 17 g is exactly half of the molar mass (34 g). So the volume must be half of 22.4 dm³. Always compare the given mass to the molar mass first, because it can save you time in the exam.