Zinc reacts with aqueous sulfuric acid to form hydrogen gas: Zn (s) + H₂SO₄ (aq) → ZnSO₄ (aq) + H₂ (g)
In an experiment, 225 mL of wet H₂ is collected over water at 27°C and a barometric pressure of 748 torr. How many grams of Zn have been consumed? The vapor pressure of water at 27°C is 26.74 torr.

Question

Quizplus · Accepted Answer

First, calculate the pressure of dry hydrogen gas by subtracting the vapor pressure of water from the barometric pressure: 748 torr - 26.74 torr = 721.26 torr. Convert this pressure to atm: 721.26 torr / 760 torr/atm = 0.949 atm. Use the ideal gas law (PV = nRT) to find moles of H₂: n = PV/RT = (0.949 atm)(0.225 L) / (0.0821 L·atm/mol·K)(300 K) = 0.00867 mol H₂. Since the reaction is 1:1, moles of Zn = moles of H₂ = 0.00867 mol. Convert moles of Zn to grams: 0.00867 mol × 65.38 g/mol = 0.567 g Zn.

Zinc Reacts with Aqueous Sulfuric Acid to Form Hydrogen Gas