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Heat of Formation

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Question

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

A

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

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B

+ 266 k J m o l^{- 1}

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C

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

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D

+ 256 k J m o l^{- 1}

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Solution

The correct option is C $- 266 k J m o l^{- 1}$
We are given:
$C H_{3} O H (g) \to C H_{3} O H (l); Δ H = 38 k J m o l^{- 1}$

$C (g) + 4 H (g) + O (g) \to C H_{3} O H (g);$ $Δ H = - (3 \times 415 + 356 + 463) = - 2064 k J m o l^{- 1}$

$C (g r a p h i t e) \to C (g);$ $Δ H = 715 k J m o l^{- 1}$

$2 H_{2} (g) \to 4 H (g);$
$Δ H = 2 \times 2 \times 218 = 872 k J m o l^{- 1}$

$\frac{1}{2} O_{2} (g) \to O (g);$ $Δ H = 249 k J m o l^{- 1}$

Adding all the above equations we get our desired equation.: $C (g r a p h i t e) + 2 H_{2} (g) + \frac{1}{2} O_{2} (g) \to C H_{3} O H (l)$ $Δ H = S u m o f a l l = Δ H^{'} s - 266 k J m o l^{- 1}$

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Similar questions

Q. Compute the heat of formation of liquid methyl alcohol (in kJ mol

^{- 1}

) using the following data. The heat of vaporisation of liquid methyl alcohol is 38 kJ mol

^{- 1}

The heat of formation of gaseous atoms from the elements in their standard states:

H =

^{- 1}

C = 715

^{- 1}

O = 249

^{- 1}

Average bond energies:

C - H = 415

^{- 1}

C - O = 356

^{- 1}

O - H = 463

^{- 1}

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}

Q. Compute the heat of formation of liquid methyl alcohol in kilojoules per mole using the following data.
The heat of vaporisation of liquid methyl alcohol =

38 k J / m o l

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

H, 218 k J / m o l

C, 715 k J / m o l

O, 249 k J / m o l

.
Average bond energies:

C - H = 415 k J / m o l

C - O = 365 k J / m o l

O - H = 463 k J / m o l

.

Q. Compute the enthalpy of formation of liquid methyl alcohol in kJ mol

^{- 1}

, using the following data.

Enthalpy of vaporisation of liquid

C H_{3} O H = 38

Enthalpy of formation of gaseous atoms from the elements in their standard states are

H \to 218

C \to 715

O \to 249

Average Bond energies

C - H \to 415

C - O \to 356

O - H \to 463

Q. Compute the heat of formation of liquid methyl alcohol in kilojoules per mole using the following data.
The heat of vaporisation of liquid methyl alcohol =

38 k J / m o l

.
The heats of formation of gaseous atoms from the elements is their standard states:

H, 218 k J / m o l

C, 713 k J / m o l

O, 249 k J / m o l

.
Average bond energies:

C - H = 415 k J / m o l

C - O = 365 k J / m o l

O - H = 463 k J / m o l

.

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Heat of Formation

Standard XIII Chemistry

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