Question

a 5.00 g sample of octane is burnt in a bomb calorimeter containing 200.00g of water. how much energy in(a) cal (b) in joules is released if the temperature of the water increases 6.00 °C?
b) What is Delta H for the above reaction in kj/mol?
c) if Delta H for the following reaction is -90kj/mol, what is how much heat is re release of 35.0 g of carbon is burnt is an excess of oxygen?

C + O2== CO2

Answer 1

Q = m c ∆T
Q = quantity of heat in joules (J)
m = mass of the substance acting as the environment in
grams (g) = 200 gm
c = specific heat capacity (4.19 for H2O) in J/(g ^oC)
∆T = change in temperature = Tfinal - Tinitial in ^oC = 6 ^oC

Q = 200 x 4.18 x 6 = 5016 Joules

5.016 Kilo joules of heat was released.

Delta H for the above reaction

Molar mass of octane = 114.23 g /mol

Delta H of the reaction = 5016 x 114.23 / 5 = - 114595 Joules or -114.595 Kilo Joules

Question C

Delta H for the reaction = -90kj/mol

Molar mass of Carbon = 12 g / mol

Heat realesed for 35 gm Carbon = - 90 x 35 /12 = -262.5 Kilo Joules