Question

Review Constants Periodic Table Benzoic acid of mass 1.45 g is reacted with oxygon in a constant volume calorimeter to form H20(l) and CO2 (g) at 298 K The mass of the water in the inner bath is 1.70 x 10g The temperature of the calorimeter and its contents rises 2.82 K as a result of this reaction. Part A K Cp.m(H2O,1) - 75.3 J. mol Calculate the calorimeter constant. The standard enthalpy of combustion of benzoic acid at 298 K is-3227 kJ mol Express your answer with the appropriate units. kJ Cal=5.21 K Previous Answers Request Answer Submit * Incorrect; Try Again; One attempt remaining

Answer 1

Molar mass of benzoic acid = 122.12 g/mol

Moles of benzoic acid that were burnt = mass / molar mass = 1.45 / 212.12 = 6.84 * 10^-3 moles

Energy releases = moles * Enthalpy of combustion = 6.84 * 10^-3 * 3227 KJ = 6.84 * 10^-3 * 3227 * 10³ J = 22072.68 J

Heat released by combustion = heat absorbed by water + heat absorbed by calorimeter

22072.68 = moles of water * Specific heat of water * temeprature change + calorimeter constant * temperature change

Moles of water = mass / molar mass = 1700 / 18 = 94.44 moles

22072.68 = 94.44 * 75.3 * 2.82 + C * 2.82

Solving, C = 715.86 J / K = 0.716 KJ/K