Question

we use enthalpy of combustion of benzoic acid as the standard for determination heat capacity of water for volume bomb calorimeters. how did we determined enthalpy of combustion of benzoic acid?

Answer 1

This can be done via:

-Qcombustion = Qwater + Qcalorimeter

substitute datA:

-moles of acid * Hcomb acid = mass of water * Cp water * (Tfinal - Tinitial) + Specific Heat of Calorimter*(Tfinal - Tinitial)

Note that

right side is all known, i.e. amount of water, Cp water, Temperatues, and speicifc heat

moles of acid can be related via molar mass + mass

then

HCombustion of acid is the oonly unkown

-moles of acid * Hcomb acid = mass of water * Cp water * (Tfinal - Tinitial) + Specific Heat of Calorimter*(Tfinal - Tinitial)

Hcomb acid = [mass of water * Cp water * (Tfinal - Tinitial) + Specific Heat of Calorimter*(Tfinal - Tinitial)] / -moles of acid