Skip to main content
Ch.10 - Gases: Their Properties & Behavior
Chapter 10, Problem 72a

Hydrogen gas can be prepared by reaction of zinc metal with aqueous HCl: Zn(s) + 2 HCl(aq) ¡ ZnCl2(aq) + H2(g) (a) How many liters of H2 would be formed at 742 mm Hg and 15 °C if 25.5 g of zinc was allowed to react?

Verified step by step guidance
1
Determine the number of moles of zinc (Zn) using its molar mass.
Use the stoichiometry of the balanced chemical equation to find the moles of hydrogen gas (H_2) produced.
Convert the temperature from Celsius to Kelvin by adding 273.15 to the Celsius temperature.
Use the ideal gas law, PV = nRT, to solve for the volume of hydrogen gas (H_2) in liters. Remember to convert pressure from mm Hg to atm by dividing by 760.
Substitute the known values into the ideal gas law equation and solve for the volume of H_2.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
4m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced chemical equation. In this case, the balanced equation shows that one mole of zinc reacts with two moles of hydrochloric acid to produce one mole of hydrogen gas. Understanding stoichiometry allows us to determine the amount of hydrogen gas produced from a given mass of zinc.
Recommended video:
Guided course
01:16
Stoichiometry Concept

Ideal Gas Law

The Ideal Gas Law relates the pressure, volume, temperature, and number of moles of a gas through the equation PV = nRT. This law is essential for calculating the volume of hydrogen gas produced under specific conditions of pressure and temperature. By rearranging the equation, we can solve for volume when the number of moles of hydrogen is known.
Recommended video:
Guided course
01:15
Ideal Gas Law Formula

Gas Laws and Conditions

Gas laws describe the behavior of gases under various conditions. In this problem, we need to consider the pressure (742 mm Hg) and temperature (15 °C) to find the volume of hydrogen gas produced. Converting temperature to Kelvin and pressure to atmospheres may be necessary to apply the Ideal Gas Law correctly, ensuring accurate calculations.
Recommended video:
Guided course
01:43
Combined Gas Law