1.)The enthalpy of combustion of benzoic acid (C_66H_55CO_22H) is –3243 kJ/mol.

Question

1.)The enthalpy of combustion of benzoic acid (C_66H_55CO_22H) is –3243 kJ/mol. The burning of 1.707 g of benzoic acid in a calorimeter causes the temperature to increase by 2.843 °C. What is the heat capacity (in kJ/°C) of the calorimeter?

2.)If 1.785 g of ethanol (CH_33CH_22OH) is burned in a constant volume calorimeter causing a temperature increase of 4.32^{circ}C, then what is the molar heat of combustion in units of kJ/mol of ethanol? (Heat capacity of the calorimeter is 9.49 kJ/^{circ}C.)

3.) Which of the following explains why the bomb calorimeter exemplifies the First Law of Thermodynamics.

A It requires the slow flow of heat energy and information is not lost

B The loss of heat energy from the sample becomes the gain in heat energy of the water bath

C It operates under standard isobaric conditions

PLEASE EXPLAIN ANSWERS IM LOST IN THIS CHAPTER

Explanation / Answer

1. Calculate the moles of benzoic acid, (molar mass = 122.12 g/ mol)

moles = mass / molar mass = 1.707 / 122.12 = 0.014 moles of benzoic acid

the heat of combustion is 3243 kJ/mol

multiply heat of combustion by the moles of benzoic acid

3243 * 0.014 = 45.402 KJ

Heat = heat capacity calorimeter * (temperature difference)

45.402 = Heat capacity calorimeter * 2.843

Heat capacity calorimeter = 45.402 / 2.843 = 15.97 kJ / C

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