The heat of combustion of acetylene is 312 kcal- If heat of formation of CO2 and H2O are 94-38 and 68-38 kcal respectively- C - C bond energy is x kcal- Given that heat of atomisation of C and H are 150-0 and 51-5 kcal respectively and C- -H bond energy is 93-64 kcal- Value of x

The correct option is A 161Given, #160; #160; C_2H_2 + (5/2)O_2⟶ 2CO_2 + H_2O; #160; Δ H = 312 kcal #160; #160; #160; ... (i) #160; # ...

You visited us 1 times! Enjoying our articles? Unlock Full Access!

Byju's Answer

Standard XII

Physics

Calorimetry

The heat of c...

Question

The heat of combustion of acetylene is 312 kcal. If heat of formation of $C O_{2}$ and $H_{2} O$ are 94.38 and 68.38 kcal respectively, $C \equiv \equiv C$ bond energy is $x k c a l$ . Given that heat of atomisation of C and H are 150.0 and 51.5 kcal respectively and $C - - H$ bond energy is 93.64 kcal. Value of $x$

161

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

150

No worries! We‘ve got your back. Try BYJU‘S free classes today!

170

No worries! We‘ve got your back. Try BYJU‘S free classes today!

None of these

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Open in App

Solution

The correct option is A 161
Given,
$C_{2} H_{2} + (5 / 2) O_{2} ⟶ 2 C O_{2} + H_{2} O; Δ H = - 312 k c a l$ ... (i)
( $∵$ Heat of combustion are exothermic)

$C + O_{2} ⟶ C O_{2}; Δ H = - 94.38 k c a l$ ... (ii)

$H_{2} + \frac{1}{2} O_{2} ⟶ H_{2} O; Δ H = - 68.38 k c a l$ ... (iii)

Multiply eq. (ii) by 2 and add in eq. (iii)

$2 C + H_{2} + (5 / 2) O_{2} ⟶ 2 C O_{2} + H_{2} O; Δ H = - 257.14 k c a l$ ...( iv)

Subtracting eq. (i) from eq. (iv)

$C_{2} H_{2} + (5 / 2) O_{2} ⟶ 2 C O_{2} + H_{2} O; Δ H = - 312 k c a l$ ...( i)
- - - - +
........................................................................................................................
$2 C + H_{2} ⟶ C_{2} H_{2}; Δ H = + 54.86 k c a l$ ... (v)

Also $Δ H$ for $C + H_{2} ⟶ C_{2} H_{2}$

$Δ H = B o n d e n e r g y d a t a o f f o r m a t i o n o f b o n d + B o n d e n e r g y d a t a o f d i s s o c i a t i o n o f b o n d$

$Δ H = - [e_{(C \equiv \equiv C)} + 2 \times e_{(C - - H)}] + [2 C_{s \to g} + e_{(H - - H)}]$

Also given, $C_{s \to g} = 150 k c a l$

$\frac{1}{2} H_{2} (g) ⟶ H (g) - 51.5 k c a l$

$∴ e_{H - - H} = 51.5 \times 2 k c a l = 103.0 k c a l$

$e_{C - - H} = 93.64 k c a l$

$∴ 54.86 = - [e_{(C \equiv \equiv C)} + 2 \times 93.64] + [2 \times 150 + 1 \times 103.0]$

$∴ e_{C \equiv \equiv C} = 160.86 k c a l$

Suggest Corrections

Similar questions

Q. The heat of combustion of acetylene is 312 kcal. If heat of formation of

C O_{2}

and

H_{2} O

are 94.38 and 68.38 kcal respectively,

C \equiv \equiv C

bond energy is

x k c a l

. Given that heat of atomisation of C and H are 150.0 and 51.5 kcal respectively and

C - - H

bond energy is 93.64 kcal.

Value of

x

(nearest integer value) is _______.

Q. The heat of formation of ethane is

- 19.46 K c a l

. Bond energies of

H - - H

C - - H

, and

C - - C

bonds are

104.18

99.0

and

80.0 K c a l

, respectively. If the heat of atomisation of graphite is x then find out the value of x.

Q. The standard heat of combustion of ethene gas is

- 330 K c a l m o l^{- 1}

. Calculate

C = C

bond energy (in kcal/mol) assuming that bond energy of

C - H

bond is

93.6 K c a l m o l^{- 1}

Given :

Δ H_{f}^{0}

for

C O_{2} (g)

and

H_{2} O (l)

are

- 94.2

and

- 61 K c a l m o l^{- 1}

respectively. Heat of atomisation of carbon and hydrogen are

150

and

51.5 K c a l m o l^{- 1}

respectively.

Δ H_{f}

C_{2} H_{4} = 12.5 k c a l

Heat of atomisation of

C = 171 k c a l

. Bond energy of

H_{2} = 104.3 k c a l

. Bond energy

C - H = 99.3 k c a l

. What is

C = C

bond energy?

Q. Heat of atomisation of

N H_{3}

and

N_{2} H_{4}

are

x k c a l m o l^{- 1}

and

y k c a l m o l^{- 1}

respectively. Average bond energy of

N - - N

bond is:

Join BYJU'S Learning Program

The heat of combustion of acetylene is 312 kcal. If heat of formation of CO2 and H2O are 94.38 and 68.38 kcal respectively, C≡≡C bond energy is xkcal. Given that heat of atomisation of C and H are 150.0 and 51.5 kcal respectively and C−−H bond energy is 93.64 kcal. Value of x