The standard enthalpy of formation of octane $(C_{8} H_{18})$ is $- 250 kJ/mol$ . Calculate the enthalpy of combustion of $C_{8} H_{18}$ . Given that enthalpy of formation of $C O_{2} (g)$ and $H_{2} O (l)$ are $- 394 kJ/mol$ and $- 286 kJ/mol$ respectively.

- 5200 kJ/mol

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

- 5726 kJ/mol

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

- 5476 kJ/mol

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

- 5310 kJ/mol

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

Open in App

Solution

The correct option is C $- 5476 kJ/mol$
According to the question,
$8 C (graphite) + 9 H_{2} (g) \to C_{8} H_{18} (g); Δ H_{f}^{\circ} = - 250 kJ/mol . . . . . . (i) C (graphite) + O_{2} (g) \to C O_{2} (g); Δ H_{f}^{\circ} = - 394 kJ/mol . . . . . . (i i) H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (l); Δ H_{f}^{\circ} = - 286 kJ/mol . . . . . . (i i i)$
The reaction of combustion of octane is $C_{8} H_{18} (g) + \frac{25}{2} O_{2} \to 8 C O_{2} (g) + 9 H_{2} O (l) . . . . . (i v)$
The $equation (i v)$ can be obtained by $8 \times equation (i i) + 9 \times equation (i i i) - equation (i)$
$∴ Δ H_{combustion}^{\circ} = 8 \times (- 394) + 9 \times (- 286) - (- 250) = - 5476 kJ/mol$

Suggest Corrections

Similar questions

The standard enthalpy of formation of octane (C₈H₁₈) is −250 kJ/mol. Calculate the enthalpy of combustion of C₈H_18.
Given : enthalpy of formation of CO₂(g) and H₂O(l) are −394 kJ/mol and −286 kJ/mol respectively:

Q. The standard enthalpies of formation of

{C O}_{2} (g), H_{2} O (l)

and glucose(s) at

25^{o} C

are

- 400 k J / m o l, - 300 k J / m o l

and

- 1300 k J / m o l

respectively. The standard enthalpy of combustion per gram of glucose at

25^{o} C

is:

Q. From the following data, calculate the enthalpy change for the combustion of cyclopropane at 298 K. The enthalpy of formation of

C O_{2} (g), H_{2} O (l)

and propane (g) are -393.5, -285.8 & 20.42 kJ/mol respectively. The enthalpy of isomerisation of cyclopropane to propene is -33.0 kJ/mol.

Q. The standard enthalpies of formation of

C O_{2} (g)

H_{2} O (l)

and glucose(s) at

25^{o}

C are

- 400

kJ/mol,

- 300

kJ/mol and

- 1300

kJ/mol, respectively. The standard enthalpy of combustion per gram of glucose at

25^{o}

C is:

The standard enthalpies of formation of $C O_{2} (g)$ , $H_{2} O (l)$ and glucose(s) at $25^{\circ} C$ are $- 400 k J / m o l$ , $- 300 k J / m o l$ and $- 1300 k J / m o l$ , respectively. The standard enthalpy of combustion per gram of glucose at $25^{\circ} C$ is

Join BYJU'S Learning Program

The standard enthalpy of formation of octane (C8H18) is −250 kJ/mol. Calculate the enthalpy of combustion of C8H18. Given that enthalpy of formation of CO2(g) and H2O(l) are −394 kJ/mol and −286 kJ/mol respectively.

The standard enthalpy of formation of octane $(C_{8} H_{18})$ is $- 250 kJ/mol$ . Calculate the enthalpy of combustion of $C_{8} H_{18}$ . Given that enthalpy of formation of $C O_{2} (g)$ and $H_{2} O (l)$ are $- 394 kJ/mol$ and $- 286 kJ/mol$ respectively.