1. Tardigrade
  2. Question
  3. Chemistry
  4. On the basis of the following thermochemical data: (Δ f GoH+(aq)=0) H2O(ℓ) arrow H+(aq)+OH-(aq); Δ H=57.32kj H2(g)+(1/2)O2(g) arrow H2O(ℓ); Δ H=-286.20kj The value of enthalpy of formation of OH− ion at 25o C is :

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Q. On the basis of the following thermochemical data $: \left(\Delta f G^{o}H^{+}_{\left(aq\right)}=0\right)$
$H_{2}O\left(\ell\right) \rightarrow H^{+}\left(aq\right)+OH^{-}\left(aq\right); \Delta H=57.32kj$
$H_{2}\left(g\right)+\frac{1}{2}O_{2}\left(g\right) \rightarrow H_{2}O\left(\ell\right); \Delta H=-286.20kj$
The value of enthalpy of formation of $OH^−$ ion at $25^o\,C$ is :

AIEEEAIEEE 2009Thermodynamics

Solution:

By adding the two given equations, we have
$H_{2\left(g\right)}+\frac{1}{2}O_{2\left(g\right)} \rightarrow H^{+}_{\left(aq\right)}+OH^{-}_{\left(aq\right)}; \Delta H=-228.88\,Kj$
Here $\Delta H^{o}_{f} of H^{+}_{\left(aq\right)}=0$
$\therefore \Delta H^{o}_{f} of OH^{-}=-228.88\,kj$