Question

How much heat is released when 75 g of octane is burned completely if the enthalpy of combustion is -5,500 kJ/mol CsH18? C8H18 + 25/2 O2 O 8CO2 + 9H20 e. 5500 kJ a. 7200 kJ b. 8360 kJ c. 4.1 x 105 kJ d. 3600 kJ

Answer 1

Answer : The correct option is, (D) 3600 kJ

Explanation :

Mass of octane = 75 g

Molar mass of octane = 114.23 g/mole

Enthalpy of combustion = -5500 kJ/mol

First we have to calculate the moles of octane.

$\text{ Moles of octane}=\frac{\text{ Mass of octane}}{\text{ Molar mass of octane}}=\frac{75g}{114.23g/mole}=0.656moles$

Now we have to calculate the heat released in the reaction.

As, 1 mole of octane released heat = -5500 kJ

So, 0.656 mole of octane released heat = 0.656 × (-5500 kJ)

                                                                   = -3608 kJ

                                                                   ≈ -3600 kJ

Therefore, the heat released in the reaction is 3600 kJ