passwella.
Menu

Unilorin Post-UTME Chemistry 2024 (Model questions) Question 4

Question 4

Energy Changes

If the enthalpy of combustion of ethanol is −1370KJmol−1, what is the enthalpy change for the combustion of 100g of ethanol? (C = 12, H = 1, O = 16)

  1. A.−1370kJ
  2. B.−6014kJ
  3. C.−1500kJ
  4. D.−2978kJ
Show the answer and explanation

Answer: D (−2978kJ)

Explanation

Molar mass of C2H5OH = 46 g/mol, so 100 g is 100/46 = 2.174 mol. ΔH = 2.174 × (−1370) ≈ −2978 kJ.