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Molar and Specific Heat Capacity

Determine the...

Question

Determine the enthalpy of the reaction $C_{3} H_{8} (g) + H_{2} (g) ⟶ C_{2} H_{6} (g) + C H_{4} (g)$ at $25^{\circ} C$ using the given heat of combustion values under standard conditions. The standard heat of formation of $C_{3} H_{8} (g)$ is $- 103.8 k J m o l^{- 1}$
Compound: $H_{2} (g)$ $C H_{4} (g)$ $C_{2} H_{6} (g)$ $C (g r a p h i t e)$

$Δ H^{⊖} (k J m o l^{- 1}) :$ $- 285.8$ $- 890.0$ $- 1560.0$ $- 393.5$

H = - 55.7 k J

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H = + 55.7 k J

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H = - 5100 k J

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None of these

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Solution

The correct option is D $H = - 55.7 k J$
$(\begin{matrix} H_{2} + \frac{1}{2} O_{2} ⟶ H_{2} O \end{matrix}) \times 5 - (C H_{4} + 2 O_{2} ⟶ C O_{2} + 2 H_{2} O) - (\begin{matrix} C_{2} H_{6} + \frac{7}{2} O_{2} ⟶ 2 C O_{2} + 3 H_{2} O \end{matrix})$

$(C + O_{2} ⟶ C O_{2}) \times 3 - (3 C + 4 H_{2} ⟶ C_{3} H_{8})$
$C_{3} H_{8} + H_{2} ⟶ C_{2} H_{6} + C H_{4}$ (desired equation)

Giving similar treatment to values of $Δ H$ , we have
$(- 285.8 \times 5) - (- 890) - (- 1560) + (- 393.5 \times 3) - (- 103.8)$

$= - 1429 + 890 + 1560 - 1180.57 + 103.8 = 2553.8 - 2609.5 = - 55.7 k J$

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Similar questions

C_{3} H_{8} (g) + H_{2} (g) \to C_{2} H_{6} (g) + C H_{4} (g)

25^{\circ} C

H_{2}

C H_{4}

- 285.8

- 890.0 k J / m o l

Δ H_{c o m b (C_{2} H_{6}) (g)} = - 1560 k J / m o l

Δ H_{s u b (C) (s)} = 393.5 k J / m o l

Δ H_{f (C_{3} H_{8}) (g)} = - 103.8 k J / m o l

C_{3} H_{8} (g) + H_{2} (g) \to C_{2} H_{6} (g) + C H_{4} (g)

25^{o}

C_{2} H_{6} (g)

- 2220 k J m o l^{- 1}

H_{2}

C H_{4}

298 K

- 890.3

k J {m o l}^{- 1}, - 393.5

k J {m o l}^{- 1}, - 285.8

k J {m o l}^{- 1}

{C H}_{4 (g)}

C_{3} H_{2} (g) + H_{2} (g) \to C_{2} H_{6} (g) + C H_{4} (g) △ H^{0} = ?

$C_{2} H_{6}$ (g)	$H_{2} (g)$	$C H_{4} (g)$	C graphite	$C_{3} H_{2}$ (g)
-1560.1	-225.0	-090.0	-393.5	-2220

△ H^{0} c o m b u s t i o n (K J m o l^{- 1}

C O_{2} (g)

H_{2} O (I)

C_{3} H_{8} (g)

C_{3} H_{8} (g) + 5 O_{2} (g) \to 3 C O_{2} (g) + 4 H_{2} O (l)

Δ H_{r x n}^{\circ} = - 2221.6 k J

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Compound:	$H_{2} (g)$	$C H_{4} (g)$	$C_{2} H_{6} (g)$	$C (g r a p h i t e)$
$Δ H^{⊖} (k J m o l^{- 1}) :$	$- 285.8$	$- 890.0$	$- 1560.0$	$- 393.5$