A coffee cup calorimeter was used to conduct a neutralization reaction. A 100.0

Question

A coffee cup calorimeter was used to conduct a neutralization reaction. A 100.0 mL sample of a 0.8500 M KOH solution was added to 100.0 mL of a 0.8404 M HBr sample. Prior to mixing, the temperatures of the acid and base were both 17.68 degree C. The maximum temperature of the mixture was 23.25 degree C. The combined solution had a density of 1.02 g/mL and a specific heat of 3.822 J/g degree C. What is the heat of neutralization reaction for HBr in kJ/mol? A. +4.34 kJ/mol B. -103 kJ/mol C. -1.09 kJ/mol D. -51.6 kJ/mol E. There is not enough information given

Explanation / Answer

For

HBr + KOH = H2O + KBr

Qmix = m*C*(Tf-Ti) = 1.02*(100+100)(3.822)(23.25-17.68) = 4,342.86 J = 4.34 kJ

for

mol = MV = 100*0.8404 = 84.04 mmol = (84.04*10^-3) mol

HRXN = Q/mol = -4.34)/(84.04*10^-3) = -51.6420 kJ/mol

Choose D

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