Thermochemistry

1
Thermochemistry

• III Calculating Enthalpy
• Changes

2
Review Heat (q)

• Refers to the transfer of kinetic energy between
  objects with diff temps
• For each chemical rxn at SATP, there is a
  specific enthalpy change

3
What other factor effects the enthalpy change of
a chemical rxn?

• Amounts (moles)
• Ex match vs campfire

4
Formula for calculating heat absorbed or released
by a chem rxn

• q n ?H
• q ? heat (kJ)
• n ? amount (mol)
• ?H ? molar enthaply change (look up on table ?)

5
Ex How much heat is released when 50.0g of
methane is formed from its elements?

• 50.0g x 1 mol CH4 3.11 mol CH4
• 16.05 g
• q n ?Hf
• (3.11mol) (-74.6 KJ)
• - 232 kJ
• Since it is negative. 232 kJ of heat is released
  when methane forms from its elements

6
HW ?

• Pg 645 19 ? 23