The enthalpy change for the following reaction: H2(g) + I2(g) 2HI(g) is -9 kJmol-1 Use this information and the values in the above table to calculate the bond dissociation energy for the H-I bond
Answers
Answer:
Like we saw with pressure, many different units are used
throughout the world for energy.
4.184 Joules (J) = 1 calorie (cal)
1 kcal = 1000 calories = 1 Nutritional Calorie (Cal)
Joule (J)
calorie (cal)
erg (erg)
electron volts (eV)
British thermal unit (Btu)
Amount of
energy it takes
to raise one
gram of water
1ºC
SI unit for energy
2
2
s
kg 1 m
J 1
⋅
=
Energy in Thermochemistry
Heat (q): energy transferred from an object
with a higher temperature to an object with a
lower temperature
Work (w): energy transferred
against a force
100º C heat 50º C
Heat cannot be transferred in the opposite
direction!
Example: Combustion reactions allow
your car to move...performing work
Vroom...
Thermochemistry
In thermochemistry, the
universe is divided into two
parts:
System
Surroundings
Surroundings
Universe
System +
Surroundings
System
Surroundings
Surroundings
The system: The
physical process or
chemical reaction in
which we are interested.
We can define the
system anyway we like.
The surroundings:
Everything else in the
universe.
Energy flow between system and
surroundings
System
Surroundings
Surrou
Explanation: