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Heat Capacity

Given that bo...

Question

Given that bond energies of
$H - H$ and $C l - C l$ are $430 k J m o l^{- 1}$ and $240 k J m o l^{- 1}$ respectively and $Δ_{f} H$ for $H C l$ is -90 kJ $m o l^{- 1} .$ The bond enthalpy of $H C l$ is:

A

$245 K J m o l^{- 1}$

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B

$2909 K J m o l^{- 1}$

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C

$380 K J m o l^{- 1}$

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D

$425 K J m o l^{- 1}$

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Solution

The correct option is D
$425 K J m o l^{- 1}$

$H_{2} + C l_{2} \to 2 H C l$

One each of $H - H$ and $C l - C l$ bonds are broken whereas 2 $H - C l$ bonds are formed. Bond breaking requires energy and bond formation is always exothermic.

$[B E_{H - H} + B E_{C l - C l}] - [2 B E_{H - C l}] = Δ H_{R}$

$[430 + 240] - [2 B E_{H - C l}] = 180$

$o r 670 - 2 (B E)_{H - C l} = 850$

$⟹ B E_{H - C l} = 425 k J m o l^{- 1}$

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Similar questions

Q. Given that bond energies of

H - H

C l - C l

430 k J m o l^{- 1}

240 k J m o l^{- 1}

respectively and

Δ_{f} H

H C l

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

. Bond enthalpy of

H C l

Q. Given that bond energy of

H - H

C l - C l

430 k J

m o 1^{- 1}

240 k J

m o 1^{- 1}

respectively and heat of formation for

H C l

- 90 k J

m o 1^{- 1}

. Bond enthalpy of

H C l

Q. Given that, bond energies of

H - H

C l - C l

430 k J / m o l

240 k J / m o l

Δ H_{f}

H C l

- 90 k J / m o l

. Bond enthalpy of

H C l

Q. Bond energies of H - H and CI - CI are

430 k J m o l^{- 1}

242 k J m o l^{- 1}

Δ H_{f}

91 k J m o l^{- 1}

. What will be the bond energy of H - Cl bond (per mole value)?

Q. Calculate free energy change for the reaction at

27^{o} C

H_{2 (g)} + C l_{2 (g)} \to 2 H - C l_{(g)}

by using the bond energy and energy data.
Bond energies of

H - H, C l - C l

H - C l

435 k J m o l^{- 1}, 240 k J m o l^{- 1}

430 k J m o l^{- 1}

respectively. Standard entropies of

H_{2}, C l_{2}

H C l

131, 223

187 J K^{- 1} m o l^{- 1}

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