Using the following thermochemical data-Cs-O2g- CO2g - H- -94-0 kcalH2g-1-2O2g- H2Ol - H- -68-0 kcalCH3COOHl-2O2g- 2CO2g-2H2Ol - H- -210-0 kcalthe heat of formation of acetic acid is -

Given reactions are C(s)+O_2(g)→ CO_2(g) Δ H= 94.0 kcal....(1) H_2(g)+1/2O_2(g)→ H_2O(l) Δ H= 68.0 kcal...(2) CH_3COOH(l)+2O_2(g)→ 2CO_2(g)+2H_2O(l) ...

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Standard XIII

Chemistry

Heat of Formation

Using the fol...

Question

Using the following thermochemical data,
$C (s) + O_{2} (g) \to C O_{2} (g) Δ H = - 94.0 k c a l$
$H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (l) Δ H = - 68.0 k c a l$
$C H_{3} C O O H (l) + 2 O_{2} (g) \to 2 C O_{2} (g) + 2 H_{2} O (l) Δ H = - 210.0 k c a l$
the heat of formation of acetic acid is :

116 kcal

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-116 kcal

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-114 kcal

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114 kcal

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Solution

The correct option is C -114 kcal
Given reactions are $C (s) + O_{2} (g) \to C O_{2} (g) Δ H = - 94.0 k c a l . . . . (1)$

$H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (l) Δ H = - 68.0 k c a l . . . (2)$

$C H_{3} C O O H (l) + 2 O_{2} (g) \to 2 C O_{2} (g) + 2 H_{2} O (l) Δ H = - 210.0 k c a l . . . . (3)$

reversing the reaction 3, we get
$2 C O_{2} (g) + 2 H_{2} O (l) \to C H_{3} C O O H (l) + 2 O_{2} (g) Δ H = + 210.0 k c a l . . . . (4)$

multiplying equation (1) and (2) by 2 we get,
$2 C (s) + 2 O_{2} (g) \to 2 C O_{2} (g) Δ H = 2 \times - 94.0 k c a l . . . . . . . .5$
$2 H_{2} (g) + O_{2} (g) \to 2 H_{2} O (l) Δ H = 2 \times - 68.0 k c a l . . . . . . .6$

Add eqn. 4, 5 and 6 to obtain
$2 C (s) + 2 H_{2} (g) + O_{2} (g) \to C H_{3} C O O H (l)$

so the heat of formation of acetic acid $= 210.0 + 2 (- 94.0) + 2 (- 68.0)$
$= - 114 k c a l$

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Similar questions

Q. Using the following thermochemical data

C (S) + O_{2} (g) \to C O_{2} (g)

Δ H = - 94.0 K c a l

H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (l)

Δ H = - 68.0 K c a l

C H_{3} C O O H (l) + 2 O_{2} (g) \to 2 C O_{2} (g) + 2 H_{2} O (l)

Δ H = - 210.0 K c a l

The heat of formation of acetic acid is

Q. Calculate the heat of formation of acetic acid from the following data:
a.

C (s) + O_{2} (g) ⟶ C O_{2} (g)

Δ H = - 393.7 k J

H_{2} (g) + 1 / 2 O_{2} (g) ⟶ H_{2} O (l)

Δ H = - 285.8 k J

C H_{3} C O O H (l) + 2 O_{2} (g) ⟶ 2 C O_{2} (g) + 2 H_{2} O (l)

Δ H = - 873.2 k J

Q. From the following data of heats of combustion, find the heat of formation of

{C H}_{3} O H (l)

{C H}_{3} O H (l) + \frac{3}{2} O_{2} (g) ⟶ C O_{2} (g) + 2 H_{2} O (l); Δ H = - 726 k J

C (s) + O_{2} (g) ⟶ C O_{2} (g); Δ H = - 394 k J

H_{2} (g) + \frac{1}{2} O_{2} (g) ⟶ H_{2} O (l); Δ H = - 286 k J

From the following data of heats of combustion, find the heat of formation of

C H_{3} O H (l)

C H_{3} O H (l) + \frac{3}{2} O_{2} (g) \to C O_{2} (g) + 2 H_{2} O (l); △_{r} H^{⊖} = - 726 k J

C (s) + O_{2} (g) \to C O_{2} (g), Δ H = - 394 k J

H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (l), Δ H = - 286 k J

Q. Find the heat of formation of ethyl alcohol from following data

C (s) + O_{2} (g) ⟶ C O_{2} (g)

......

Δ H = - 94 K c a l

H_{2} (g) + I / 2 O_{2} (g) ⟶ H_{2} O (l)

;....

Δ H = - 68 K c a l

C_{2} H_{5} O H (l) + 3 O_{2} (g) ⟶ 2 C O_{2} (g) + 3 H_{2} O (l)

.....

Δ H = - 327 K c a l

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Heat of Formation

Standard XIII Chemistry

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Using the following thermochemical data, C(s)+O2(g)→CO2(g) ΔH=−94.0 kcal H2(g)+12O2(g)→H2O(l) ΔH=−68.0 kcal CH3COOH(l)+2O2(g)→2CO2(g)+2H2O(l) ΔH=−210.0 kcal the heat of formation of acetic acid is :