Question

A 12.8 g sample of ethanol (C₂H₅OH) is burned in a bomb calorimeter with a heat capacity of 5.65 kJ/°C. The temperature of the calorimeter and the contents increases from 25°C to 35°C. What is the heat of combustion per mole of ethanol? The molar mass of ethanol is 46.07 g/mol.

C2H5OH (l) + 3 O2 (g) -----> 2 CO₂ (g) + 3 H₂O (g) ΔE = ?

Answer 1

C2H5OH (l) + 3 O2 (g) -----> 2 CO₂ (g) + 3 H₂O (g)  ΔE = ?

Given that;

Mass of ethanol , m= 12.8 g

  heat capacity of ethanol, c = 5.65 kJ/°C

temperature change, dT = 35 °C-° 25 C= 10°C

The molar mass of ethanol is 46.07 g/mol

First calculate the total amount of heat as follows:

Q = c*dT

= 5.65 kJ/°C *10°C

= 56.5 KJ

= 56500 J

Now number of mole of ethanol = amount in g/ molar mass

= 12.8 g/ 46.07 g/ mole

= 0.28 moles

heat of combustion per mole of ethanol= total heat / number of moles

= 56500 J /0.28 moles

= 201785.7143 J / mole

= 201.8 J / mole