1. Thermochemistry
New unit

2. Thermochemistry
EXOTHERMIC Reaction: a reaction that releases heat to the surroundings temp of surroundings goes up ENDOTHERMIC Reaction: a reaction that absorbs heat from the surroundings temp of surroundings goes down

3. Graphically Energy Profiles Energy vs
Graphically Energy Profiles Energy vs. Reaction Pathway (as the reaction proceeds)
EXOTHERMIC Reaction
Go to smartboard
‘EXO’
A + B C + D + Δ HR
A + B - Δ HR C + D
A + B C + D Δ HR < 0 (negative)
ENDOTHERMIC Reaction
Go to smartboard
‘ENDO’
P + W G + T - Δ HR
P + W + Δ HR G + T
P + W G + T Δ HR > 0
(positive)

4. Identify the following reactions as EXO or ENDO
CH4 + O2 – 600J  CO2 + H2O
Exo
C3H8 + O2  CO2 + H2O HR = -500J
Endo
CO2 + H2O  O2 + C6H12O J
endo
N2 + Cl2  NCl3 Hr= 900 J
H2 + Cl2  HCl + 80J
exo
C4H10 + O J CO2 + H2O
Fe + CuSO4 + 10J  Cu + FeSO4
CaCl2  Ca+2 + 2Cl J
P + Cl2 + 60J  PCl3
H2O(s)  H20 (l)

5. Thermochemical Equations and Stoichiometry
smartboard

6. Homework: Finish Q’s if not done Read text pg
Homework: Finish Q’s if not done Read text pg. 298 – 300 Define: Thermochemistry Thermal Energy Chemical System Surroundings Open system Closed system

7. Heat: Q – measured in Joules
Specific Heat Capacity: c
A physical property
The amount of heat (Joules) required to raise the temp of 1g of a given substance 1ᵒC
ex.. cH2O = 4.2J/gᵒC
this means… if you want to raise the temp of 1g of H2O 1ᵒC you require 4.2J.

8. Suppose you want to raise the temp of 100g of H2O 1ᵒC NOT FINISHED!!!!

9. Thermochemistry cont’d
ΔHR = The Heat of Reaction:
The amount of heat (J) absorbed/released in a given reaction
Follow stochiometry
Eg. smartboard

10. Types of Reactions
Combustion Reactions: a substance is burned (reacted in O2)
Formation Reaction: a substance is formed (produced) from its elements in their elemental state.
Metals – atoms (copper is Cu)

11. Element
Elemental State
Hydrogen H2
Oxygen O2
Nitrogen N2
Chlorine
Cl2
Carbon
C (graphite)
Fluorine F2
Metals M
Eg. Formation reaction for NaHCO3
Na + H2 + C + O2  NaHCO3

12. ΔHcombustion of ‘x’ : Heat of Combustion of X:
the amount of heat absorbed or released when 1 MOLE of a given subsance (x) burns (reacts in oxygen). J/mole
ΔHformation of X: Heat of Formation of X:
The amount of heat absorbed or released when 1 mole of a given substance (X) is formed from its elements in their elemental states. J/mole
ΔH solution: Heat of solution:
The amount of heat absorbed/released when 1 mole of a substance dissolves

13. ΔHneutralization:Heat of Neutralization The amount of heat absorbed/released when 1 mole of a substance is neutralized J/mole ΔHdissociation: Heat of Dissociation: The amount of heat absorbed/released when 1 mole dissociates (breaks down into its atoms) J/mole Go to smartboard

14. WRIGHTS Method: Calorimetry
Measuring heats of reaction (ΔHR)
The reaction is carried out in a reaction vessel. The amount of heat absorbed / released is measured by analysing what happens to the surroudings and the vessel.
thermometer
Reaction Vessel
water

15. Apply 1st Law of Thermodynamics
Energy (heat) is neither created nor destroyed
Qabsorbed/released = Q released / absorbed by the
by the reaction surroundings
Det. ΔHR using calorimietry is applying the 1st Law of Thermodynamics
Surroundings  calculate Q using Q = mc Δt

16. Smartbaord examples.