Thermochemical .pdf - Thermochemical equation An equation...

Thermochemical equation
An equation that includes the quantity of energy released or absorbed as heat during the
reaction as written.
A reaction in which energy is released (produced) is called exothermic reaction.
A + B C + D + Energy
A reaction in which energy is absorbed (added) is called endothermic reaction.
A + B + Energy C + D
Example
2H
2 (g)
+ O
2 (g)
2H
2
O
(g)
+ 483.6kJ (exothermic reaction)
CO
2 (g)
+ 283.0 kJ CO
(g)
+ ½ O
2 (g)
(endothermic reaction)
Identify whether the reaction is Exothermic or Endothermic
Exothermic reaction Endothermic reaction
E
reactants
is greater than E
products
E
reactants
is less than E
products
Δ H
reaction
is negative Δ H
reaction
is positive
A B + Energy A + Energy B
A B Δ H = ( - ) value A B Δ H = ( + ) value
Energy is released Energy is added

Application 1
I-Classify the following reactions as endothermic or exothermic reactions
a. C + O
2
→ CO
2
+ 393.5 kJ _____ exothermic _________________
b. 2H
2
O
(l)
+ 571.8 kJ → 2H
2 (g)
+ O
2 (g)
__________ endothermic ___________
c. C
(graphite, s)
+ ½ O
2(g)
→ CO
(g)
Δ H= -110.5kJ ________ exothermic _____________
d. H
2
O( l ) → H
2
O( g ) Δ H
m
= 44 kJ mol
–1
________ endothermic ______________
Application 2
Upon adding solid potassium hydroxide pellets to water the following reaction
takes place: KOH( s ) → KOH( aq ) + 43 kJ
Answer the following questions regarding the addition of 14.0 g of KOH to water:
a.
Does the beaker get warmer or colder?