How many grams of zinc metal are required to produce 4.00 liters of hydrogen gas at STP according to the chemical equation shown below? Zn(s)+ 2 HCl(aq)→ ZnCl₂(aq)+ H₂(g)

Question

Quizplus · Accepted Answer

According to the balanced equation, 1 mole of Zn produces 1 mole of H2 gas. 
At STP, 1 mole of gas occupies 22.4 L. 
Therefore, to produce 4.00 L of H2 gas, we need:
4.00 L / 22.4 L/mol = 0.179 moles of H2 gas.

Since the mole ratio between Zn and H2 is 1:1, we need 0.179 moles of Zn. 
The molar mass of Zn is 65.38 g/mol. 
Therefore, the mass of Zn needed is:

0.179 mol x 65.38 g/mol = 11.7 g

Thus, the best choice is B.

How Many Grams of Zinc Metal Are Required to Produce