Download presentation

Presentation is loading. Please wait.

1
**Calculating heat changes**

Section 11.4

2
**After reading Section 11.4, you should know:**

What Hess’s Law is How to apply Hess’s Law to a chemical equation How to calculate the heat of formation for a given chemical equation

3
Hess’s Law The heat of 2 reactions added together will equal the heat of a 3rd reaction Adding 2 equations together…you can cancel compounds out IF they are exactly the same on the reactants and products side 2Al + 11/2 O2 --> Al2O H = kJ Fe2O3 --> 2Fe /2 O H = kJ 2Al + Fe2O3 --> 2Fe + Al2O H = kJ

4
**Hf = standard heat of formation**

Hf = standard heat of formation Change in enthalpy when 1 mol of new compounds form under standard conditions Table of values on page 316 Ex: Calculate the H0 for NO(g) + O2 --> 2NO2 Hf NO = kJ / mol Hf O2 = 0.0 kJ / mol Hf NO2 = kJ / mol

5
**You should have gotten: -113.04 kJ / mol**

1. Find sum of Hf reactants Remember, you have 2 moles of NO 2. Find sum of Hf products 3. Find the difference between Hf products and Hf reactants You should have gotten: kJ / mol

6
**After reading Section 11.4, you should know:**

What Hess’s Law is How to apply Hess’s Law to a chemical equation How to calculate the heat of formation for a given chemical equation

Similar presentations

Presentation is loading. Please wait....

OK

THERMOCHEMISTRY CP Unit 9 Chapter 17.

THERMOCHEMISTRY CP Unit 9 Chapter 17.

© 2019 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google