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?

20.62 Kilo-joules

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

100cm, because 11.0 cm is 3 figures as they've chosen to include the decimal point. if you have a 3 digit number then anything after the second digit will become 0 if it's to 2 significant figures

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