Calorimetry - Jan14 Class

Calorimetry
- To measure heat absorbed/released by water we need to know 3 things:
1) Temperature change °C
2) Amount of water (g, kg, ml, L)
3) Specific heat capacity (kJ/kg °C)

∆H = mC∆T
m = mass of water
C = specific heat capacity 4.19kJ/kg °C
∆T = change in temperature

Examples: Calculate the heat required to warm 400g of water from 20°C to 50°C
∆H = mC∆T
∆H = (0.400kg)(4.19 kJ/kg °C)(50° - 30°)
∆H = 50 kJ

75.0 kJ are added to 850 ml of water initially at 25.0°C. What will the final temperature be?

∆H = mC∆T

∆H = mC (Tf - Ti)

Molar Enthalpy: Heat absorbed/released by one mole

When a candle (C25H52) is burnt, heat is released according to the reaction:
C25H52 + 38 O2 -> 25 CO2 + 26 H2O + 11 000 kJ
If 1.0g of wax is burnt, how much energy is released?
1.0g x 1.0mol/352g = 0.00284mol

11 000kJ / 1mol C25H52 x 0.00284 mol C25H52 = 31.3 kJ

CALORIMETRY OF A BOMB!