## Chemistry and Chemical Reactivity (9th Edition)

$-136.3\ kJ/mol$
From the definition of heat capacity: $(650\ g\times 4.184\ J/g.K+550\ J/K)\times(22.3-18.5)\ K=12.4\ kJ$ With a negative sign since the temperature raises. Number of moles of ethanol: $4.20\ g\div 46.07\ g/mol=0.091\ mol$ Hence: $-12.4\ kJ\div 0.096\ mol=-136.3\ kJ/mol$