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Heat of Formation

On the basis ...

Question

On the basis of the following thermochemical data: $(Δ_{f} G^{0} (H)_{(a q)}^{+} = 0)$
$H_{2} O (l) ⟶ H^{+} (a q) + O H^{-} (a q); Δ H = 57.32 k J$
$H_{2} (g) + \frac{1}{2} O_{2} (g) ⟶ H_{2} O (l); Δ H = - 286.20 k J$
The value of enthalpy of formation of $O H^{-}$ ion at $25^{o} C$ is:

A

- 228.51 k J

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B

- 198.51 k J

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C

+ 238.5 k J

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D

- 238.5 k J

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Solution

The correct option is B $- 228.51 k J$
Solution:- (A) $- 228.88 k J$
Given:-

${H_{2} O}_{(l)} ⟶ {H^{+}}_{(a q .)} + {O H}^{-}_{(a q .)} Δ H = 57.32 k J . . . . . (1)$

${H_{2}}_{(g)} + \frac{1}{2} {O_{2}}_{(g)} ⟶ {H_{2} O}_{(l)} Δ H = - 286.20 k J . . . . . (2)$

Adding ${e q}^{n} (1) & (2)$ , we have

${H_{2} O}_{(l)} + {H_{2}}_{(g)} + \frac{1}{2} {O_{2}}_{(g)} ⟶ {H^{+}}_{(a q .)} + {O H}^{-}_{(a q .)} + {H_{2} O}_{(l)}; Δ H = (57.32) + (- 286.20) k J$

${H_{2}}_{(g)} + \frac{1}{2} {O_{2}}_{(g)} ⟶ {H^{+}}_{(a q .)} + {O H}^{-}_{(a q .)}; Δ H = - 228.88 k J$

Hence the value of enthalpy of formation of ${O H}^{-}$ ion at $25 ℃$ is $- 228.88 k J$ .

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Similar questions

H_{2} O (l) \to H^{+} (a q) + O H^{-} (a q); Δ H = 57.32 k J

H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (l); Δ H = - 286.02 k J

Then, calculate the enthalpy of formation of

O H^{-}

25^{o} C

Q. On the basis of the following thermochemical data

H_{2} O_{(g)} ⟶ H_{(a q)}^{+} + {O H}_{(a q)}^{-}; Δ H = 57.32 k J

H_{2 (g)} + \frac{1}{2} O_{2 (g)} ⟶ H_{2} O_{(l)}; Δ H = - 286.2 k J

The value of enthalpy of formation of

{O H}^{-}

25^{o} C

;

H_{2} O (l) \to H^{+} (a q) + O H^{-} (a q); Δ H = 57.32

H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (l); Δ H = - 286.02

Then calculate the enthalpy of formation of

O H^{-}

25^{o}

Q. Consider the following reactions :

H^{+} (a q) + O H^{-} (a q) = H_{2} O (l); Δ H = - X_{1} k J . m o l^{- 1}

H_{2} (g) + \frac{1}{2} O_{2} (g) = H_{2} O (l); Δ H = - X_{2} k J . m o l^{- 1}

C O_{2} (g) + H_{2} (g) = C O (g) + H_{2} O (l); Δ H = + X_{3} k J . m o l^{- 1}

C_{2} H_{2} (g) + \frac{5}{2} O_{2} (g) = 2 C O (g) + H_{2} O (l); Δ H = + X_{4} k J . m o l^{- 1}

Enthalpy of formation of

H_{2} O (l)

Q. Consider the following reactions:

(i) H^{+} (a q) + O H^{-} (a q) \to H_{2} O (l), Δ H = - X_{1} {kJ mol}^{- 1}

(i i) H_{2} (g) + \frac{1}{2} O_{2} (a q) \to H_{2} O (l), Δ H = - X_{2} {kJ mol}^{- 1}

(i i i) C O_{2} (g) + H_{2} (g) \to C O (g) + H_{2} O (l), Δ H = - X_{3} {kJ mol}^{- 1}

(i v) C_{2} H_{2} (g) + \frac{5}{2} O_{2} (g) \to 2 C O_{2} (g) + H_{2} O (l), Δ H = X_{4} {kJ mol}^{- 1}

Enthalpy of formation of

H_{2} O (l)

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