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Hess' Law

The following...

Question

The following two reactions are known
$F e_{2} O_{3 (s)} + 3 C O_{(g)} \to 2 F e (s) + 3 C O_{2 (g)}$ ; $Δ H = - 26.8 k J$
$F e O_{(s)} + C O_{(g)} \to F e_{(s)} + C O_{2 (g)} Δ H = - 16.5 k J$

The value of $Δ H$ for the following reaction is:
$F e_{2} O_{3 (s)} + C O_{(g)} \to 2 F e O_{(s)} + C O_{2 (g)}$

A

+ 10.3 kJ

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B

- 43.3 kJ

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C

- 10.3 kJ

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D

+ 6.2 kJ

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Solution

The correct option is D + 6.2 kJ
Given :
(I) Fe $_{2}$ O $_{3 (s)}$ + 3CO $_{(g)}$ $\to$ 2Fe(s) + 3CO $_{2 (g)}$ ; $Δ$ $H = - 26.8 k J$
(II) FeO $_{(s)}$ + CO $_{(g)}$ $\to$ Fe $_{(s)}$ + CO $_{2 (g)}$ ; $Δ$ $= - 16.5 k J$
On multiplying equation (II) with 2, we get
(III) 2FeO $_{(s)}$ + 2CO $_{(g)}$ $\to$ 2Fe $_{(s)}$ + 2CO $_{2 (g)}$ ; $Δ$ $H = - 33 k J$
On substracting equation (IIII) from, I we get
(IV) Fe $_{2}$ O $_{3 (s)}$ + CO $_{(g)}$ $\to$ 2FeO $_{(s)}$ + CO $_{2 (g)}$ ; $Δ$ $H = - 26.8 - (- 33) k J = + 6.2 k J$
The value of $Δ$ H for the reaction (IV) is + $6.2 k J .$

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Similar questions

Q. The following two reactions are known

F e_{2} O_{3 (s)} + 3 C O_{(g)} \to 2 F e_{(s)} + 3 C O_{2 (g)}; Δ H = - 26.8 k J

F e O_{(s)} + C O_{(g)} \to F e_{(s)} + C O_{2 (g)}; Δ H = - 16.5 k J

Δ H

for the following reaction

F e_{2} O_{3 (s)} + C O_{(g)} \to 2 F e O_{(s)} + C O_{2 (g)}

Q. From the following data at

25^{\circ} C

, The standard enthalpy of formation of FeO(s) is X, then 0.3-X is:

Reaction	$Δ_{r} H^{\circ}$ ( kJ / mole )
$F e_{2} O_{3} (s) + 3 C (g r a p h i t e) \to 2 F e (s) + 3 C O (g)$	492.6
$F e O (s) + C (g r a p h i t e) \to F e (s) + C O (g)$	155.8
$C (g r a p h i t e) + O_{2} (g) \to C O_{2} (g)$	$-$ 393.51
$C O (g) + 1 / 2 O_{2} (g) \to C O_{2} (g)$	$-$ 282.98

Q. Given the following thermos chemical reactions:

X O_{2} (s) + C O (g) \to X O (s) + C O_{2} (g)

Δ H = - 20.0

X_{3} O_{4} (s) + C O (g) \to 3 X O (s) + C O_{2} (g)

Δ H = + 6.0

3 X_{2} O_{3} (s) + C O (g) \to 2 X_{3} O_{4} (s) + C O_{2} (g)

Δ H = - 12.0

Δ H

in kJ for the reaction.

2 X O_{2} (s) + C O (g) \to X_{2} O_{3} (s) + C O_{2} (g)

.

Q. Determine the heat of the following reaction:

F e O (s) + F e_{2} O_{3} (s) \to F e_{3} O_{4} (s)

Given informations:

2 F e (s) + O_{2} (g) \to 2 F e O (s); Δ H^{\circ} = - 544 k J 4 F e (s) + 3 O_{2} (g) \to 2 F e_{2} O_{3} (s); Δ H^{\circ} = - 1648.4 k J F e_{3} O_{4} (s) \to 3 F e (s) + 2 O_{2} (g); Δ H^{\circ} = + 1118.4 k J

In the reaction,

C O_{2} (g) + H_{2} (g) \to C O (g) + H_{2} O (g);

Δ H = 2.8 K J

Δ H

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