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Byju's Answer

Standard XII

Chemistry

Hess' Law

The bond ener...

Question

The bond energies of $C - C$ , $C = C$ , $H - H$ and $C - H$ linkages are $350$ , $600$ , $400$ and $410$ kJ/mol respectively. The heat of hydrogenation of ethylene is:

- 170

kJ/mol

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- 400

kJ/mol

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- 260

kJ/mol

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- 450

kJ/mol

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Solution

The correct option is A $- 170$ kJ/mol
$C_{2} H_{2}      1 C = C + 4 C - H + H_{2}    1 H - H ⟶ C_{2} H_{6}      1 C - C + 6 C - H$
$Δ H_{r e a c t i o n} = Δ H_{C - C}^{B E} + 6 Δ H_{C - H}^{B E} - Δ H_{H - H}^{B E} - Δ H_{C = C}^{B E} - 4 Δ H_{C - H}^{B E}$
$⟹ Δ H_{r e a c t i o n} = 350 + 2 \times 410 - 400 - 600$
$⟹ Δ H_{r e a c t i o n} = 170$ $k J / m o l$
$Δ H_{h y d r o g e n a t i o n}^{- 2 H_{6}} = - Δ H_{r e a c t i o n} = - 170$ $k J / m o l$

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Similar questions

Q. The bond energies of

C - C, C = C, H - H

and

C - H

are

350, 600, 400

and

410 kJ/mol

respectively. The heat of hydrogenation of ethylene is:

Q. The enthalpies of atomization of

C H_{4} (g)

and

C_{2} H_{6} (g)

are respectively

400 k J m o l^{- 1}

and

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

The value of

△ H_{C - C}

would be

Q. Using the data provided, calculate the multiple bond energy

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

of a

C \equiv C

bond in

C_{2} H_{2} .

Given that the heat of formation of

C_{2} H_{2} = 225 k J m o l^{- 1} .

(take the bond energy of

C - H

bond as

350 k J m o l^{- 1}

2 C (s) \to 2 C (g) △ H = 1410 k J m o l^{- 1}

H_{2} (g) \to 2 H (g) △ H = 330 k J m o l^{- 1}

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:

Q. What is the heat of formation of liquid methyl alcohol in

k J m o l^{- 1},

use the following data.
Heat of vaporization of liquid methyl alcohol =

38 k J m o l^{- 1}

.
Heat of formation of gaseous atoms from the elements in their standard states:

H = 218 k J m o l^{- 1}, C = 715 k J m o l^{- 1}, O = 249 k J m o l^{- 1}

Average bond energies :

C - H = 415 k J m o l^{- 1} C - O = 356 k J m o l^{- 1} O - H = 463 k J m o l^{- 1}

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The bond energies of C−C, C=C, H−H and C−H linkages are 350, 600, 400 and 410 kJ/mol respectively. The heat of hydrogenation of ethylene is:

The bond energies of $C - C$ , $C = C$ , $H - H$ and $C - H$ linkages are $350$ , $600$ , $400$ and $410$ kJ/mol respectively. The heat of hydrogenation of ethylene is: