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.
