This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Calculating an unknown H involves three steps: Identify the target equation, the step whose H is unknown, and note the number of moles of reactants and products. Manipulate the equations for which H is known so that the target numbers of moles of reactants and products are on the correct sides. Remember to:Change the sign of H when you reverse an equation.Multiply number of moles and H by the same factor. Add the manipulated equations to obtain the target equation. All substances except those in the target equation must cancel. Add their H values to obtain the unknown H. Problem: Nitrogen oxides undergo many interesting reactions. Calculate H for the overall equation 2NO 2 ( g ) + 0.5O 2 ( g ) N 2 O 5 ( s ) from the following information. N 2 O 5 ( s ) 2NO( g ) + 1.5O 2 ( g ) H = 223.7 kJ NO( g ) + 0.5O 2 ( g ) NO 2 ( g ) H = 57.1 kJ 2...
View
Full
Document
This note was uploaded on 04/13/2008 for the course CHM 2045 taught by Professor Mitchell during the Fall '07 term at University of Florida.
 Fall '07
 Mitchell
 Chemistry, Stoichiometry

Click to edit the document details