A 0.1413 g sample of solidmagnesium is burned in a bomb calorimeter that has a h

Question

A 0.1413 g sample of solidmagnesium is burned in a bomb calorimeter that has a heat capacityof 1769 J/°C. The calorimeter contains exactly 341 g of water, and the temperature increases by1.126°C.
Calculate the heat given off by the burning Mg, in kJ/g and inkJ/mol.
A 0.1413 g sample of solidmagnesium is burned in a bomb calorimeter that has a heat capacityof 1769 J/°C. The calorimeter contains exactly 341 g of water, and the temperature increases by1.126°C.
Calculate the heat given off by the burning Mg, in kJ/g and inkJ/mol.

Explanation / Answer

Heat given out by burning of magnesium is absorbed bycalorimeter and water. Heat absorbed by calorimeter = Heat capacity * temperaturedifference                                              = 1769 J/ C * 1.126 C                                              = 1991.89 J Heat absorbed by water = mass * specifc heat * temperaturedifference                                      = 341 g * 4.18 J/g. C * 1.126 C                                      = 1604.97 J So total heat given = 1991.89 J + 1604.97 J = 3596.86 J =3.596 J This is the heat given for 0.1413 g Heat given for 1 g = 3.596 / 0.1413 = 25.45 kJ/g Moles of magnesium = mass / atomic mass                                = 0.1413 g / 24.3 g/mol                                = 0.0058 mol Heat given for 1 mol = 3.596 kJ / 0.0058 mol = 620kJ/mol

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