Question

A 35.6 g sample of ethanol (c2h5oh) is burned in a bomb calorimeter, according to the following reaction. if the temperature rose from 35.0 to 76.0°c and the heat capacity of the calorimeter is 23.3 kj/°c, what is the value of δh°rxn? the molar mass of ethanol is 46.07 g/mol.

Answer 1

Answer is: molar heat of reaction of combustion of ethanol is 1237.435 kJ/mol.
m(C₂H₅OH) = 35.6 g.
n(C₂H₅OH) = m(C₂H₅OH) ÷ M(C₂H₅OH).
n(C₂H₅OH) = 35.6 g ÷ 46.07 g/mol.
n(C₂H₅OH) = 0.772 mol.
ΔT = 76.0°C - 35.0°C = 41°C.
Q = ΔT · C.
Q = 41°C · 23.3 kJ/°C.
Q = 955.3 kJ.
ΔH = Q / n(C₂H₅OH).
ΔH = 955.3 kJ / 0.772 mol.
ΔH = 1237.435 kJ/mol.