A bomb calorimeter may be calibrated using a substance with a well-known heat of combustion. A commonly used calibrating agent is benzoic acid (C6H5O2) which has a heat of combustion of 3227 kJ for each mole of benzoic acid. 2.50 g of pure solid benzoic acid is placed in a calorimeter and completely reacted with oxygen. The temperature rise of the calorimeter is observed to be 8.90°C. Calculate the calibration factor of the calorimeter in kJ°C⁻¹.

SSCE VCE Chemistry Practical Work: A bomb calorimeter may be calibr

A bomb calorimeter may be calibrated using a substance with a well-known heat of combustion - VCE - SSCE Chemistry - Question 3 - 2004 - Paper 1

Question 3

A bomb calorimeter may be calibrated using a substance with a well-known heat of combustion. A commonly used calibrating agent is benzoic acid (C6H5O2) which has a h... show full transcript

Worked Solution & Example Answer:A bomb calorimeter may be calibrated using a substance with a well-known heat of combustion - VCE - SSCE Chemistry - Question 3 - 2004 - Paper 1

Step 1

2.50 g of pure solid benzoic acid

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Answer

To begin, calculate the number of moles of benzoic acid used. The molar mass (RMM) of benzoic acid (C6H5O2) is approximately 122 g/mol. Therefore, the number of moles is calculated as follows:

ext{Moles of benzoic acid} = rac{ ext{mass}}{ ext{molar mass}} = rac{2.50 ext{ g}}{122 ext{ g/mol}} \\ = 0.0205 ext{ mol}

Step 2

Calculate energy released

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Next, determine the energy released by the combustion of the benzoic acid using its heat of combustion:

ext{Energy released} = ext{moles} imes ext{heat of combustion} = 0.0205 ext{ mol} imes 3227 ext{ kJ/mol} \\ = 66.13 ext{ kJ}

Step 3

Calibration factor calculation

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Finally, calculate the calibration factor of the calorimeter using the temperature change observed:

ext{Calibration factor} = rac{ ext{Energy released}}{ ext{Temperature rise}} = rac{66.13 ext{ kJ}}{8.90 ext{ °C}} \\ = 7.43 ext{ kJ/°C}

Thus, the calibration factor of the calorimeter is 7.43 kJ/°C.

A bomb calorimeter may be calibrated using a substance with a well-known heat of combustion - VCE - SSCE Chemistry - Question 3 - 2004 - Paper 1

Worked Solution & Example Answer:A bomb calorimeter may be calibrated using a substance with a well-known heat of combustion - VCE - SSCE Chemistry - Question 3 - 2004 - Paper 1

2.50 g of pure solid benzoic acid

Calculate energy released

Calibration factor calculation

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