Chemical Thermodynamics Question 419

Question: When 1 mole of oxalic acid is treated with excess of $ NaOH $ in dilute aqueous solution, $ 106kJ $ of heat is liberated. Predict the enthalpy of ionisation of the acid

Options:

A) $ 4.3kJmo{{l}^{-1}} $

B) $ -4.3,kJ,mo{{l}^{-1}} $

C) $ 8.6kJ,mo{{l}^{-1}} $

D) $ -8.6,kJ,mo{{l}^{-1}} $

Show Answer

Answer:

Correct Answer: C

Solution:

  • $ {{H}^{+}}(aq)+O{{H}^{-}}(aq)\leftrightharpoons H_2O(l); $

$ \Delta H=-57.3kJ $ …. (i) $ H_2C_2O_4+2O{{H}^{-}}\leftrightharpoons C_2O_4^{-}+2H_2O;\Delta H=-106kJ $ …. (ii) For the second reaction the value should have been $ 2\times ( -57.3 )=-114.6kJ $ The difference $ ( 114.6-106 )=8.6kJ,mo{{l}^{-1}} $ is used to effect of the ionisation of oxalic acid.



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