Chemistry 231
Weekly Quiz (?) #1
G. Marangoni
September 17, 2009.
Answer the following questions in the time allotted. There are no tricks on this quiz, so
don’t look for any. Marks are indicated in the [
]
Name:
ID# :
1. Calculate the standard enthalpy change for the following reaction. [3 marks]
SO2 (g) + ½ O2 (g)  SO3 (g)
Substance
SO2 (g)
SO3 (g)
fH (kJ/mole)
-296.9
-395.2
rH = fH [SO3 (g)] - fH [SO2 (g)]
= 1 mole x -395.2 kJ/mole – 1 mole x -296.9 kJ/mole
= -98.3 kJ/mole
2. A 0.900 g sample of phenol (C6H5OH) was burned in a bomb calorimeter with a total
heat capacity of 11.73 kJ/ C. Calculate the molar enthalpy of combustion of phenol
given that the temperature inside the calorimeter increased by 2.50C. [7 marks]
Note – n(phenol) = 0.900 g / (94.11 g/mole)
= 0.00956 mole of phenol
- q rxn = (qH2O + qcal)
= (Ccal + CH2O) x t
= (11.73 kJ/C) x 2.50 C
= - 29325 J = -29.32 kJ
 qrxn = -29.32 kJ
combH  -29.32 kJ / 0.00967 mole
= -3.07 x 103 kJ combH