Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 5: Problem 70

Write balanced equations that describe the formation of the following compounds from elements in their standard states, and use Appendix \(\mathrm{C}\) to obtain the values of their standard enthalpies of formation: (a) \(\mathrm{H}_{2} \mathrm{O}_{2}(g)\) (b) \(\mathrm{CaCO}_{3}(s)\) (c) \(\mathrm{POCl}_{3}(l),(\mathbf{d}) \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(l)\)

Short Answer

Expert verified
(a) Formation of H2O2 (g): \[\frac{1}{2}\mathrm{H}_{2}(g) + \frac{1}{2}\mathrm{O}_{2}(g) \rightarrow \mathrm{H}_{2}\mathrm{O}_{2}(g)\], ΔHf° = -187.8 kJ/mol. (b) Formation of CaCO3 (s): \[\mathrm{Ca}(s) + \mathrm{C}(s, graphite) + \frac{3}{2}\mathrm{O}_{2}(g) \rightarrow \mathrm{CaCO}_{3}(s)\], ΔHf° = -1206.9 kJ/mol. (c) Formation of POCl3 (l): \[\frac{1}{4}\mathrm{P}_{4}(s, white) + \frac{3}{2}\mathrm{Cl}_{2}(g) + \frac{1}{2}\mathrm{O}_{2}(g) \rightarrow \mathrm{POCl}_{3}(l)\], ΔHf° = -542.6 kJ/mol. (d) Formation of C2H5OH (l): \[2\mathrm{C}(s, graphite) + 3\mathrm{H}_{2}(g) + \frac{1}{2}\mathrm{O}_{2}(g) \rightarrow \mathrm{C}_{2}\mathrm{H}_{5}\mathrm{OH}(l)\], ΔHf° = -277.6 kJ/mol.

Step by step solution

01

a) Formation of H2O2 (g) from elements in standard states

(1) Write down the elements in standard states: H2 (g) and O2 (g). (2) Combine the elements to form H2O2 (g): H2 (g) + O2 (g) -> H2O2 (g). (3) Balance the equation: 1/2 H2 (g) + 1/2 O2 (g) -> H2O2 (g). (4) Look up the standard enthalpies of formation of H2O2 (g) in Appendix C: ΔHf° = -187.8 kJ/mol.
02

b) Formation of CaCO3 (s) from elements in standard states

(1) Write down the elements in standard states: Ca (s), C (s, graphite), and O2 (g). (2) Combine the elements to form CaCO3 (s): Ca (s) + C (s, graphite) + O2 (g) -> CaCO3 (s). (3) Balance the equation: Ca (s) + C (s, graphite) + 3/2 O2 (g) -> CaCO3 (s). (4) Look up the standard enthalpies of formation of CaCO3 (s) in Appendix C: ΔHf° = -1206.9 kJ/mol.
03

c) Formation of POCl3 (l) from elements in standard states

(1) Write down the elements in standard states: P4 (s, white), Cl2 (g), and O2 (g). (2) Combine the elements to form POCl3 (l): P4 (s, white) + Cl2 (g) + O2 (g) -> POCl3 (l). (3) Balance the equation: 1/4 P4 (s, white) + 3/2 Cl2 (g) + 1/2 O2 (g) -> POCl3 (l). (4) Look up the standard enthalpies of formation of POCl3 (l) in Appendix C: ΔHf° = -542.6 kJ/mol.
04

d) Formation of C2H5OH (l) from elements in standard states

(1) Write down the elements in standard states: C (s, graphite), H2 (g), and O2 (g). (2) Combine the elements to form C2H5OH (l): C (s, graphite) + H2 (g) + O2 (g) -> C2H5OH (l). (3) Balance the equation: 2 C (s,graphite) +3 H2 (g) + 1/2 O2 (g) -> C2H5OH (l). (4) Look up the standard enthalpies of formation of C2H5OH (l) in Appendix C: ΔHf° = -277.6 kJ/mol.

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

An aluminum can of a soft drink is placed in a freezer. Later, you find that the can is split open and its contents frozen.Work was done on the can in splitting it open. Where did the energy for this work come from?

You may have noticed that when you compress the air in a bicycle pump, the body of the pump gets warmer. (a) Assuming the pump and the air in it comprise the system, what is the sign of \(w\) when you compress the air? (b) What is the sign of \(q\) for this process? (c) Based on your answers to parts (a) and (b), can you determine the sign of \(\Delta E\) for compressing the air in the pump? If not, what would you expect for the sign of \(\Delta E\) ? What is your reasoning? [Section 5.2\(]\)

Given the data $$ \begin{aligned} \mathrm{N}_{2}(g)+\mathrm{O}_{2}(g) & \longrightarrow 2 \mathrm{NO}(g) & & \Delta H=+180.7 \mathrm{~kJ} \\ 2 \mathrm{NO}(g)+\mathrm{O}_{2}(g) & \longrightarrow 2 \mathrm{NO}_{2}(g) & & \Delta H=-113.1 \mathrm{~kJ} \\ 2 \mathrm{~N}_{2} \mathrm{O}(g) & \longrightarrow 2 \mathrm{~N}_{2}(g)+\mathrm{O}_{2}(g) & \Delta H &=-163.2 \mathrm{~kJ} \end{aligned} $$ use Hess's law to calculate \(\Delta H\) for the reaction $$ \mathrm{N}_{2} \mathrm{O}(g)+\mathrm{NO}_{2}(g) \longrightarrow 3 \mathrm{NO}(g) $$

The standard enthalpies of formation of gaseous propyne \(\left(\mathrm{C}_{3} \mathrm{H}_{4}\right),\) propylene \(\left(\mathrm{C}_{3} \mathrm{H}_{6}\right),\) and propane \(\left(\mathrm{C}_{3} \mathrm{H}_{8}\right)\) are +185.4 \(+20.4,\) and \(-103.8 \mathrm{~kJ} / \mathrm{mol}\), respectively. (a) Calculate the heat evolved per mole on combustion of each substance to yield \(\mathrm{CO}_{2}(g)\) and \(\mathrm{H}_{2} \mathrm{O}(g)\) (b) Calculate the heat evolved on combustion of \(1 \mathrm{~kg}\) of each substance. (c) Which is the most efficient fuel in terms of heat evolved per unit mass?

A watt is a measure of power (the rate of energy change) equal to \(1 \mathrm{~J} / \mathrm{s}\). (a) Calculate the number of joules in a kilowatt- hour. (b) An adult person radiates heat to the surroundings at about the same rate as a 100 -watt electric incandescent lightbulb. What is the total amount of energy in kcal radiated to the surroundings by an adult in 24 hours?
See all solutions

Recommended explanations on Chemistry Textbooks

Inorganic Chemistry

Read Explanation

Chemical Analysis

Read Explanation

Kinetics

Read Explanation

Ionic and Molecular Compounds

Read Explanation

Chemical Reactions

Read Explanation

Making Measurements

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