Question

One mole of ethanol when burnt in oxygen, gives out a: kJ $ mo{{l}^{-1}} $ heat. If one mole of $ {{O}_{2}} $ is used, what will be the amount of heat evolved?

• A. $ x\,kJ $
• B. $ \frac{x}{3}\,kJ $
• C. $ 3x\,kJ $
• D. $ \frac{3x}{2}\,kJ $

Answer 1

Answer: (B)

$ {{C}_{2}}{{H}_{5}}OH+3{{O}_{2}}\xrightarrow{{}}2C{{O}_{2}}+3{{H}_{2}}O;\Delta H=-xkJ $ By burning with 3 moles of $ {{O}_{2}} $ heat evolved $ =-xkJ $ $ \therefore $ by burning with 1 mole of $ {{O}_{2}} $ heat evolved $ =-\frac{x}{3}kJ $