Written 7.docx - Name James Burton College ID Thomas Edison...

Name: James Burton
College ID:
Thomas Edison State University
General Chemistry I with Labs (CHE-121)
Section no.:
Semester and year:
Written Assignment 7: Energy and Thermochemistry
Answer all assigned questions and problems, and show all work.
1. Consider this reaction:
2CH
3
OH( l ) + 3O
2
( g ) → 4H
2
O( l ) + 2CO
2
( g ) ∆ H = –1452.8 kJ/mol
1. Is this reaction endothermic or exothermic? (2 points)
2. What is the value of ∆ H if the equation is multiplied throughout by 2? (2 points)
3. What is the value of ∆ H if the direction of the reaction is reversed so that the
products become the reactants and vice versa? (2 points)
4. What is the value of ∆ H if water vapor instead of liquid water is formed as the
product? (2 points)
2. The first step in the industrial recovery of zinc from the zinc sulfide ore is roasting, that
is, the conversion of ZnS to ZnO by heating:
2ZnS( s ) + 3O
2
( g ) → 3ZnO( s ) + 2SO
2
( g ) ∆ H = –879 kJ/mol
Calculate the heat evolved (in kJ) per gram of ZnS roasted. (5 points)
97.47g
.(Reference: Chang 6.25)

3. A 6.22 kg piece of copper metal is heated from 20.5 °C to 324.3 °C. Calculate the heat