Ch.6 - Gases

Tro - Chemistry: A Molecular Approach 6th Edition

Tro6th EditionChemistry: A Molecular ApproachISBN: 9780137832217Not the one you use?Change textbook

Tro 6th Edition

Ch.6 - Gases

Problem 77

Chapter 6, Problem 77

The zinc in a copper-plated penny will dissolve in hydrochloric acid if the copper coating is filed down in several spots (so that the hydrochloric acid can get to the zinc). The reaction between the acid and the zinc is 2 H⁺(aq) + Zn(s) → H₂(g) + Zn²⁺(aq). When the zinc in a certain penny dissolves, the total volume of gas collected over water at 25 °C is 0.951 L at a total pressure of 748 mmHg. What mass of hydrogen gas is collected?

Verified step by step guidance

Identify the reaction: \(2 \text{H}^+ (\text{aq}) + \text{Zn}(\text{s}) \rightarrow \text{H}_2(\text{g}) + \text{Zn}^{2+}(\text{aq})\).

Use the ideal gas law \(PV = nRT\) to find the number of moles of \(\text{H}_2\) gas. Remember to convert the pressure to atm and the volume to liters.

Adjust the pressure for the vapor pressure of water at 25 °C, which is 23.8 mmHg. Subtract this from the total pressure to get the pressure of the \(\text{H}_2\) gas.

Convert the temperature from Celsius to Kelvin by adding 273.15 to the Celsius temperature.

Calculate the mass of \(\text{H}_2\) using the number of moles from the ideal gas law and the molar mass of hydrogen gas (2.02 g/mol).

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Was this helpful?

Key Concepts

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

Gas Laws

Gas laws describe the behavior of gases in relation to pressure, volume, and temperature. The ideal gas law, PV = nRT, relates these variables, where P is pressure, V is volume, n is the number of moles, R is the ideal gas constant, and T is temperature in Kelvin. Understanding these relationships is crucial for calculating the amount of gas produced in a chemical reaction.

Stoichiometry

Stoichiometry involves the calculation of reactants and products in chemical reactions based on balanced equations. It allows us to determine the amount of substances consumed and produced, using mole ratios derived from the balanced chemical equation. In this case, stoichiometry helps relate the moles of hydrogen gas produced to the moles of zinc that reacted.

Collecting Gas Over Water

When gas is collected over water, the total pressure measured includes the vapor pressure of water. To find the pressure of the gas alone, the vapor pressure of water at the given temperature must be subtracted from the total pressure. This adjustment is essential for accurate calculations of the gas volume and subsequent mass determination.

Recommended video:

Guided course

01:23

Reaction with Water

Related Practice

Textbook Question

Consider the chemical reaction:

C(s) + H₂O(g) → CO(g) + H₂(g)

How many liters of hydrogen gas are formed from the complete reaction of 22.5 g C? Assume that the hydrogen gas is collected at a pressure of 1.00 atm and a temperature of 355 K.

views

Textbook Question

A heliox deep-sea diving mixture contains 2.0 g of oxygen to every 98.0 g of helium. What is the partial pressure of oxygen when this mixture is delivered at a total pressure of 8.5 atm?

3290

views

Textbook Question

The hydrogen gas formed in a chemical reaction is collected over water at 30.0 °C at a total pressure of 732 mmHg. What is the partial pressure of the hydrogen gas collected in this way? If the total volume of gas collected is 722 mL, what mass of hydrogen gas is collected?

Consider the chemical reaction: 2 H₂O(l) → 2 H₂(g) + O₂(g) What mass of H₂O is required to form 1.85 L of O₂ at a temperature of 315 K and a pressure of 0.981 atm?

Textbook Question

What is the mole fraction of oxygen gas in air (see Table 6.3)? What volume of air contains 20.0 g of oxygen gas at 273 K and 1.00 atm?

views

Textbook Question

The air in a bicycle tire is bubbled through water and collected at 25 °C. If the total volume of gas collected is 5.45 L at a temperature of 25 °C and a pressure of 745 torr, how many moles of gas were in the bicycle tire?

1692

views