The enthalpy change for the reaction, (aq) + (aq) → (aq) + (l) is -57 kJ. Predict the value of the enthalpy change in the following reaction: Ba(OH)2(aq) + (aq) → (s) + 2(l)

Question

The enthalpy change for the reaction, $NaOH$(aq) + $HCl$(aq) → $NaCl$(aq) + $H_2O$(l) is -57 kJ. Predict the value of the enthalpy change in the following reaction: Ba(OH)2(aq) + $H_2SO_4$(aq) → $BaSO_4$(s) + 2$H_2O$(l)

Prashant Kotian · Accepted Answer

Correct answer: D. The reaction Ba(OH)2(aq) + (aq) → (s) + 2(l) involves two processes:
1) Neutralization: 2H^+(aq) + 2OH^-(aq) → 2(l), which is the neutralization of 2 equivalents, releasing 2 × (-57 kJ) = -114 kJ.
2) Precipitation: Ba^2+(aq) + SO4^2-(aq) → (s). The precipitation of a solid salt is an exothermic process, which releases additional heat. Therefore, the net enthalpy change will be significantly more negative than -114 kJ, which corresponds to option (d) (-200 kJ).

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