A0.1375-g sample of magnesium is burned in a constant-volume bomb calorimeter that has a heat capacity of 1769 j 0 c-1. the calorimeter contains exactly 300 g of water, and the temperature increases by l.1 26°c. calculate the heat given off by the burning magnesium, in kj g-1 and in kj moj-1

1) 24.76 kJ/g

2)  597.4 kJ/mol

Explanation:

Let the heat released during reaction be q.

q = Heat gained by water

m = Mass of water= 300 g

c = Heat capacity of water = 4.184 J/g°C

Change in temperature = ΔT = 1.126 °C

Heat gained by bomb calorimeter =

Heat capacity of bomb calorimeter , C = 1769J/g°C

Change in temperature = ΔT'= 1.126 °C

Total heat released during reaction is equal to total heat gained by water and bomb calorimeter.

Thus 0.1375 g of magnesium releases 3.405 kJ of heat

1 g of magnesium releases = of heat

Thus heat given off by the burning magnesium, in kJ/g is 24.76.

Moles of magnesium =

 moles of magnesium releases 3.405 kJ of heat

1 mole of magnesium releases = of heat

Thus heat given off by the burning magnesium, in kJ/mol is 597.4.

thermal energy is the answer