Question

When 1.020 g of ethanol (C2H6O, 46.07 g/mol) was burned in a bomb calorimeter containing 2400. g of water, the temperature of the water rose from 22.46 to 25.52ºC.   The specific heat of water is 4.18 J/g-°C. What is the enthalpy of combustion of 1 mol of ethanol? What is the heat capacity of the calorimeter?

Answer 1

Given

Mass of ethanol = 1.020 g

Molar mass = 46 g/mol

No. of moles = Mass of ethanol / Molar mass = 1.020 g / 46 g/mol = 0.0222 moles

Mass of water = 2400 g

Molar mass of water = 18 g/mol

No. of moles of water = 2400 g / 18 g/mol = 133.33 moles

Specific heat of water Cp = 4.18 J/g.C

Intial Temperature = 22.46 C

FInal temperature T2 = 25.52 C

heat released from ethanol = heat absorbed by water = (m*Cp*(T2-T1)) of water

heat released from ethanol = 2400 g * 4.18 J/g.C ( 25.52 - 22.46) C = 30697.92 J

0.0222 moles of ethanol released  30697.92 J

so Enthalpy of combustion of 1 mole of ethanol =  30697.92 J / 0.0222 moles = 1382.79 KJ//mol Answer