Calorimetry
To measure heat absorbed/released by water we need to know THREE important things
1) Temperature change ( 'C)
2) Amount of water (g,kg, mL, L)
3) Specific heat capacity (KJ/ Kg 'C)
deltaH= mCdeltaT
m= mass of water
C= specific heat capacity
deltaT= change of temperature *liquid water is 4.19 KJ/Kg '
MOLAR ENTHALPY
Heat obsorbed/ realeased by one mole
When a candle (C H ) is burnt, heat is released according to reaction"
25 52
C H + 380 ---> 25CO + 26H O+ 11000 KJ
25 52 2 2 2
ex. 9.0 grams of charcoal were completely consumed in a bomb calorimeter. If 2.0 L of water absorbed all of the heat released by the charcoal, and if the temperature of the water increased from 20.25 to 56.04oC, what is the molar enthalpy of carbon?
Answer: deltaH= mCdeltaT
= 2000g(4.19 J/(g C))(56.04-20.25)
= 299 920 J
dH = - C = - 299 920 J = -299.92 kJ
n = 9.0g / 12.01 g/mole = 0.7493 mole
DH/n = -299.92 kJ/ 0.7493 mole = -400.27kJ/mole of C = - 4.0 X 102 kJ/mole
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