Question

A)A reaction in aqueous solution is run in a calorimeter and it is found that the the solution gains 57 kJ of heat and the calorimeter gains 9 kJ of heat. What is the heat gained or lost by the reaction (q_rxn) in kJ? (If it is negative, include the negative sign. If it is positive, include nothing)

B)In a reaction of a potential new fuel, it is found that when 2.84 moles of the fuel combusts, 1,625 kJ of energy is released. What is the delta H_rxn for the combustion of the fuel in units of kJ/mol?

Answer 1

Answer – A) solution gain = 57 kJ , calorimeter gain = 9 kJ

We know the when reaction in aqueous solution is run in a calorimeter the total released is equal heat gain by solution and calorimeter

So, total heat gain = heat gain by solution + heat gain by calorimeter

                              = 57 kJ + 9 kJ

                              = 66 kJ

We know heat gain = heat loss

So, total heat loss = - 66 kJ

B) Released energy = -1625 kJ

Moles = 2.84

The negative sign for the showing the energy is released.

We are asking for energy in kJ/mol and it is as follow –

the combustion of the fuel in units of kJ/mol = -1625 kJ / 2.84 moles

                                                                         = - 572.18 kJ/mol