Question

Enthalpy of combustion of ethyl alcohol, C2 H5 OH, is – 950 kJ mol–1. How much heat is evolved when one gram of ethyl alcohol burns?​

Answer 1

20.62 Kilo-joules

Step-by-step explanation:

• The Enthalpy of combustion of ethyl alcohol is -950 kJ/mol.
• This means that 1 mole of ethyl alcohol evolves a quantity of heat of 950 Joules when burned.

Molar mass of ethyl ethanol = 46.08 g/mol

Therefore;

46.08 g of C₂H₅OH evolves heat equivalent to 950 kilojoules

We can calculate the amount of heat evolved by 1 g of C₂H₅OH

Heat evolved by 1 g of C₂H₅OH = Molar enthalpy of combustion ÷ Molar mass

= 950 kJ/mol ÷ 46.08 g/mol

= 20.62 Kj/g

Therefore, a gram of C₂H₅OH will evolve 20.62 kilo-joules of heat