The heat of neutralisation of HCl by NaOH is -55.9 kJ/mol, the energy of dissociation of HCN is:

Question

The heat of neutralisation of HCl by NaOH is -55.9 kJ/mol, the energy of dissociation of HCN is: (A) 43.8 kJ (B) -43.8 kJ (C) -68 kJ (D) 68 kJ

Tardigrade Admin · Accepted Answer

Given H ++ OH - arrow H 2 O Δ H=-55.9 kJ ...(i) HCN + OH - arrow H 2 O + CN - Δ H=-121 kJ ...(ii) on reversing (i) we get H 2 O longrightarrow H ++ OH - Δ H=+55.9 kJ ...(iii) on adding (iii) to (ii) we get HCN longrightarrow H ++ CN - Δ H=+43.8 kJ

Q. The heat of neutralisation of $H Cl$ by $N a O H$ is $- 55.9 k J / m o l,$ the energy of dissociation of $H CN$ is:

43.8 kJ

-43.8 kJ

-68 kJ

68 kJ

Given $H^{+} + O H^{-} \to H_{2} O$
$Δ H = - 55.9 k J$ ...(i)
$H CN + O H^{-} \to H_{2} O + C N^{-}$
$Δ H = - 121 k J$ ...(ii)
on reversing (i) we get
$H_{2} O ⟶ H^{+} + O H^{-}$
$Δ H = + 55.9 k J$ ...(iii)
on adding (iii) to (ii) we get
$H CN ⟶ H^{+} + C N^{-}$
$Δ H = + 43.8 k J$

Q. The heat of neutralisation of HCl by NaOH is −55.9kJ/mol, the energy of dissociation of HCN is: