Respuesta :
Answer: 1) 24.76 kJ/g
2) 597.4 kJ/mol
Explanation:
Let the heat released during reaction be q.
[tex]q=m\times c\times \Delta T[/tex]
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
[tex]q=300\times 4.184\times 1.126=1413.3J[/tex]
Heat gained by bomb calorimeter = [tex]q_{cal}[/tex]
Heat capacity of bomb calorimeter , C = 1769J/g°C
Change in temperature = ΔT'= 1.126 °C
[tex]q_{cal}=m_{cal}\times c_{cal}\times \Delta T=C_{bomb}\times \Delta T=1769\times 1.126=1991.9J[/tex]
Total heat released during reaction is equal to total heat gained by water and bomb calorimeter.
[tex]q_{combustion}=-(q_{water}+q_{cal}[/tex]
[tex]q_{combustion}=-(1413.3+1991.9)J[/tex]
[tex]q=3405J=-3.405kJ[/tex]
Thus 0.1375 g of magnesium releases 3.405 kJ of heat
1 g of magnesium releases =[tex]\frac{3.405}{0.1375}\times 1=24.76kJ[/tex] of heat
Thus heat given off by the burning magnesium, in kJ/g is 24.76.
Moles of magnesium =[tex]\frac{0.1375g}{24g/mol}=5.7\times 10^{-3}mol[/tex]
[tex]5.7\times 10^{-3}[/tex] moles of magnesium releases 3.405 kJ of heat
1 mole of magnesium releases =[tex]\frac{3.405}{5.7\times 10^{-3}}\times 1=597.4 kJ[/tex] of heat
Thus heat given off by the burning magnesium, in kJ/mol is 597.4.
