Calorimetry (Jan 14,2010)

To measure heat that is absorbed or released by water we need to know 3 important things:

1. Temperature change : measured in degree Celsius
2. Amount of water : measured in grams, kilograms, milliliters, & liters
3. Specific heat capacity : measured in kilojoules, per kilogram degree Celsius

The equation for this matter is :

Example: Calculate the heat required to warm 400 g of water from 20 degree Celsius to 50 degree Celsius.
H = mCT
H = (0.400 kg)(4.19 kJ/kg •C)(30 •C)
H = 50 kJ

75.0 kJ are added to 850 mL of water initially at 250 •C. What will the final temperature be?
H=mCT
H=mC(Tf-Ti)
H+Ti=Tf
mC

75.0 kJ + 250 •C
(0.850 kg)(4.19 kJ/kg •C)
Tf= 46.1 •C

Molar Enthalpy is heat absorbed or released by one mole

When a Candle (C25H52) is burnt, heat is released according to the reaction :
C25H52 + 38O2 ---> 25CO2 + 26H2O + 11000 kJ

If 1.0 g of wax is burnt, how much energy is released?

1 mol X 1.0 g = 0.00284 mol
352 g

11000 kJ X 0/00284 mol C25H52 = 31.3 kJ
1 mol C25H52