Zinc reacts with aqueous sulfuric acid to form hydrogen gas: Zn (s) + H₂SO₄ (aq) → Zn SO₄ (aq) + H₂ (g)
In an experiment, 201 mL of wet H₂ is collected over water at 27 °C and a barometric pressure of 765 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, we need to determine the partial pressure of hydrogen gas (P(H2)) using Dalton's Law of Partial Pressures:

P(H2) = P(total) - P(H2O)
P(H2) = (765 torr) - (26.74 torr) = 738.26 torr

Next, we can use the Ideal Gas Law to calculate the number of moles of hydrogen gas produced:

PV = nRT
n = (PV)/(RT)
n = [(738.26 torr)(0.201 L)]/[(0.0821 L atm/mol K)(300 K)]
n = 0.0107 mol

Since the balanced chemical equation has a 1:1 ratio of Zn to H2, we know that 0.0107 mol of Zn was consumed. Finally, we can convert moles of Zn to grams using its molar mass:

0.0107 mol Zn x (65.39 g Zn/mol) = 0.700 g Zn

Therefore, the answer is B) 0.519 (rounded to three significant figures).

Zinc Reacts with Aqueous Sulfuric Acid to Form Hydrogen Gas