STUDY GUIDE FOR THERMO TEST Thursday March 14, 2014
You may use notes; all equations will be given
Thermo chemistry: Chapter 15 in Glencoe text. Check the web site for Notes and answers to worksheets we have done.
Vocabulary to Know: Know that 1 calorie = 4.184 joules; 1 food Calorie = 1000 calories
Heat , Temperature, Specific Heat, Calorie, Heat of fusion, Heat of vaporization, Endothermic, Exothermic,
Enthalpy, Heat of reaction , heat of formation, Hess’s Law, Energy diagrams (and like page 535 and 538)
Thermochemistry calculations/problems:
1.) Heat equation: q=mC∆T
Be able to solve for heat (q) or mass, or specific heat (C), or ∆T
Example: How much heat energy is needed to raise the temperature of a 55 g sample of aluminum from 22.4⁰C to
94.6 ⁰C? The specific heat of aluminum is .89 J/g⁰C?
2.) Heat of fusion/heat of vaporization: Q= mH fus
or Q=mH vap
Be able to solve for heat (q)
Example:
How many kJ of heat are absorbed when 255.6 g of ice melts (at 0 o C)? The heat of fusion for water is 80 cal./g
3.) Calorimetry problems: (Two step calculation) Q=mC∆T for water and C= Q/m∆T for the metal
Example:
A 30.5 g piece of metal at 100⁰C is placed in 80 ml of water at 24⁰C in an insulated calorimeter. The specific heat of water is 1.0 cal/g⁰C. The metal and water came to equilibrium at a final temperature of 30⁰C. What is the specific heat of the metal?
4.) Heating curve: Be able to label the states of matter, where the temperature is changing and where a phase change is occurring. Refer to worksheet. (or data on page 531)
What happens to the temperature during a phase change?

5.) Calculating the heat of the reaction using heats of formation: Remember elements in their natural states, like the gases O
2
, F
2
, H
2
do not take any energy to form so therefore are 0 kJ/mol.
Example:
What is the heat of the reaction ∆H rxn for the following reaction if the heat of formation of O
2
is 0 kJ/mol, the heat of formation of CO is -110.5 kJ/mol, and the heat of formation of CO
2
is -393.5 kJ/mol.
2CO + O
2
→ 2CO
2
6.) Be able to solve for amount of heat produced using Stoichiometry and thermo chemical equations:
Example:
When carbon disulfide is formed from its elements, heat is absorbed. Calculate the amount of heat (in kJ) is absorbed when 5.66 grams of carbon disulfide is formed.
C(s) + 2S(s) → CS
2
(l) ∆H rxn
= 89.3 kJ
7.) Hess’s Law:
Be able to calculate the heat of the reaction from heat of the reaction from intermediate steps.
Example:
Calculate the enthalpy change (∆H rxn
) in kJ for the following reaction.
2Al(s) + Fe
2
O
3
(s) → 2Fe(s) + Al
2
O
3
(s)
The intermediate steps are:
2Al(s) + 3/2 O
2
(g) → Al
2
O
3
(s) ∆H rxn
= -1669.8 kJ
2Fe (s) + 3/2 O
2
(g) → Fe
2
O
3
(s) ∆H rxn
= -824.2 kJ

STUDY GUIDE FOR THERMO TEST Thursday March 14, 2014
You may use notes; all equations will be given
Thermo chemistry: Chapter 15 in Glencoe text. Check the web site for Notes and answers to worksheets we have done.
Vocabulary to Know: Know that 1 calorie = 4.184 joules; 1 food Calorie = 1000 calories
Heat , Temperature, Specific Heat, Calorie, Heat of fusion, Heat of vaporization, Endothermic, Exothermic,
Enthalpy, Heat of reaction , heat of formation, Hess’s Law, Energy diagrams (and like page 535 and 538) various answers
Thermochemistry calculations/problems:
1.) Heat equation: q=mC∆T
Be able to solve for heat (q) or mass, or specific heat (C), or ∆T
Example: How much heat energy is needed to raise the temperature of a 55 g sample of aluminum from 22.4⁰C to
94.6 ⁰C? The specific heat of aluminum is .89 J/g⁰C? Answer: 3534.19 J
2.) Heat of fusion/heat of vaporization: Q= m∆H fus
or Q=m∆H vap
Be able to solve for heat (q)
Example:
How many kJ of heat are absorbed when 255.6 g of ice melts (at 0 o C)? The heat of fusion for water is 80 cal./g
Answer: 2048 calories or 8560.64 joules or 8.56 kJ
3.) Calorimetry problems: (Two step calculation) Q=mC∆T for water and C= Q/m∆T for the metal
Example:
A 30.5 g piece of metal at 100⁰C is placed in 80 ml of water at 24⁰C in an insulated calorimeter. The specific heat of water is 1.0 cal/g⁰C. The metal and water came to equilibrium at a final temperature of 30⁰C. What is the specific heat of the metal? Answer: First find the heat gained by the water q=mC∆T, then find the specific heat of the metal C=q/m∆T, .26cal/g⁰C.
4.) Heating curve: Be able to label the states of matter, where the temperature is changing and where a phase change is occurring. Refer to worksheet. (or data on page 531)
What happens to the temperature during a phase change? Answer: temperature remains constant
4a) PHASE diagrams (Ch 12 page 429 and 430) Solid are low temp. and higher pressure, gases are high temp and lower pressure, liquids are in between

5.) Calculating the heat of the reaction using heats of formation: Remember elements in their natural states, like the gases O
2
, F
2
, H
2
do not take any energy to form so therefore are 0 kJ/mol.
Example:
What is the heat of the reaction ∆H rxn for the following reaction if the heat of formation of O
2
is 0 kJ/mol, the heat of formation of CO is -110.5 kJ/mol, and the heat of formation of CO
2
is -393.5 kJ/mol.
2CO + O
2
→ 2CO
2
Answer: Remember ∆H rxn=
∆H f
(Products)- ∆H f
(Reactants) = -566 kJ

H = { 2(-393.5)} – { 2(-110.5) + 2(0)} = -566 kJ; exothermic reaction
6.) Be able to solve for amount of heat produced using Stoichiometry and thermo chemical equations:
Example:
When carbon disulfide is formed from its elements, heat is absorbed. Calculate the amount of heat (in kJ) is absorbed when 5.66 grams of carbon disulfide is formed.
C(s) + 2S(s) → CS
2
(l) ∆H rxn
= 89.3 kJ
Answer: 6.63 kJ
5.66 g = .07428 mols of CS
2
; .07428mol (89.3 kJ/mol) = 6.63
kJ
7.) Hess’s Law:
Be able to calculate the heat of the reaction from heat of the reaction from intermediate steps.
Example:
Calculate the enthalpy change (∆H rxn
) in kJ for the following reaction.
2Al(s) + Fe
2
O
3
(s) → 2Fe(s) + Al
2
O
3
(s)
The intermediate steps are:
2Al(s) + 3/2 O
2
(g) → Al
2
O
3
(s) ∆H rxn
= -1669.8 kJ
2Fe (s) + 3/2 O
2
(g) → Fe
2
O
3
(s) ∆H rxn
= -824.2 kJ
Answer: -845.6 kJ ; keep 1 st the same reverse the 2 nd