Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 7: Problem 121

Which of the following substances have an enthalpy of formation equal to zero? a. \(\mathrm{Cl}_{2}(g)\) b. \(\mathrm{H}_{2}(g)\) c. \(\mathrm{N}_{2}(l)\) d. \(\mathrm{Cl}(g)\)

Short Answer

Expert verified
The substances with an enthalpy of formation equal to zero are a. \(\mathrm{Cl}_{2}(g)\) and b. \(\mathrm{H}_{2}(g)\).

Step by step solution

01

Definition of enthalpy of formation

Enthalpy of formation is the change in enthalpy during the formation of 1 mole of a compound from its constituent elements, with all substances in their standard states. The standard enthalpy of formation of an element in its most stable form is considered to be zero.
02

Analyzing each substance

a. \(\mathrm{Cl}_{2}(g)\): This substance is in its elemental form and it's a gas, which is the most stable form of chlorine. Therefore, its enthalpy of formation is zero. b. \(\mathrm{H}_{2}(g)\): This substance is in its elemental form and it's a gas, which is the most stable form of hydrogen. Therefore, its enthalpy of formation is zero. c. \(\mathrm{N}_{2}(l)\): Nitrogen in its elemental form is \(\mathrm{N}_{2}(g)\), not a liquid. Hence, its enthalpy of formation is not zero as it's not in its most stable form. d. \(\mathrm{Cl}(g)\): The most stable form of chlorine is \(\mathrm{Cl}_{2}(g)\). As a result, the enthalpy of formation for this substance is not zero.
03

Conclusion

The substances with an enthalpy of formation equal to zero are a. \(\mathrm{Cl}_{2}(g)\) and b. \(\mathrm{H}_{2}(g)\).

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

One mole of \(\mathrm{H}_{2} \mathrm{O}(g)\) at 1.00 atm and \(100 .^{\circ} \mathrm{C}\) occupies a volume of 30.6 L. When 1 mole of \(\mathrm{H}_{2} \mathrm{O}(g)\) is condensed to 1 mole of \(\mathrm{H}_{2} \mathrm{O}(l)\) at 1.00 atm and \(100 .^{\circ} \mathrm{C}, 40.66 \mathrm{kJ}\) of heat is released. If the density of \(\mathrm{H}_{2} \mathrm{O}(l)\) at this temperature and pressure is \(0.996 \mathrm{g} / \mathrm{cm}^{3},\) calculate \(\Delta E\) for the condensation of 1 mole of water at 1.00 atm and \(100 .^{\circ} \mathrm{C}\).

How is average bond strength related to relative potential energies of the reactants and the products?

One way to lose weight is to exercise! Walking briskly at 4.0 miles per hour for an hour consumes about 400 kcal of energy. How many hours would you have to walk at 4.0 miles per hour to lose one pound of body fat? One gram of body fat is equivalent to 7.7 kcal of energy. There are 454 g in 1 lb.

The heat capacity of a bomb calorimeter was determined by burning 6.79 g methane (energy of combustion \(=-802 \mathrm{kJ} / \mathrm{mol}\) \(\mathrm{CH}_{4}\)) in the bomb. The temperature changed by \(10.8^{\circ} \mathrm{C}\). a. What is the heat capacity of the bomb? b. \(A 12.6-g\) sample of acetylene, \(C_{2} H_{2},\) produced a temperature increase of \(16.9^{\circ} \mathrm{C}\) in the same calorimeter. What is the energy of combustion of acetylene (in \(\mathrm{kJ} / \mathrm{mol}\) )?

Consider a mixture of air and gasoline vapor in a cylinder with a piston. The original volume is \(40 . \mathrm{cm}^{3} .\) If the combustion of this mixture releases \(950 .\) \(\mathrm{J}\) of energy, to what volume will the gases expand against a constant pressure of \(650 .\) torr if all the energy of combustion is converted into work to push back the piston?
See all solutions

Recommended explanations on Chemistry Textbooks

Nuclear Chemistry

Read Explanation

Ionic and Molecular Compounds

Read Explanation

Inorganic Chemistry

Read Explanation

Chemical Analysis

Read Explanation

Organic Chemistry

Read Explanation

The Earths Atmosphere

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free