The energy released when 6 moles of octane is burnt in air will be [Given, ΔH_f for CO₂ (g). H₂O(g) and C₈H₁₈ (l), respectively are -490, -240 and +160J/mol]

-37.4 kJ

-20 kJ

-6.2 kJ

-35.5 kJ

Solution

-35.5 kJ

$C + O_{2} \overset{}{\to} {CO}_{2}; ∆ G = - 490 J . . . (i) H_{2} + \frac{1}{2} O_{2} \overset{}{\to} H_{2} O; ∆ H = - 240 J . . . (ii) 8 C + 9 H_{2} \overset{}{\to} C_{8} H_{18}; ∆ H = + 160 J . . . . (iii)$

On applying, 8 x Eq. (i) + 9x Eq. (ii) -Eq. (iii), we get

$C_{8} H_{18} + \frac{25}{2} O_{2} \overset{}{\to} 8 {CO}_{2} + 9 H_{2} O ∆ H_{R}^{0} = [8 x (- 490)] + [9 x (- 240)] + 160 = - 5920 J {mol}^{- 1}$

Hence, energy exchange when 6 moles of octane is burnt in air = - 5920 x 6 = -35520 J = -35.5 kJ

Some More Questions From Thermodynamics Chapter

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Thermodynamics

The energy released when 6 moles of octane is burnt in air will be [Given, ΔH_f for CO₂ (g). H₂O(g) and C₈H₁₈ (l), respectively are -490, -240 and +160J/mol]

-37.4 kJ

-20 kJ

-6.2 kJ

-35.5 kJ

Some More Questions From Thermodynamics Chapter

Define an isolated system.

Define intensive properties.

Define extensive properties.

Why all living systems need to be 'open systems'?

Define state variables of a system.

From thermodynamic point of view, to which system the animals and plants belong?

What is a state function?

A thermodynamic state function is a quantity

What is reversible process in thermodynamics?

Define irreversible change.

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NCERT Sample Papers

Entrance Exams Preparation

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Thermodynamics

The energy released when 6 moles of octane is burnt in air will be [Given, ΔHf for CO2 (g). H2O(g) and C8H18 (l), respectively are -490, -240 and +160J/mol] -37.4 kJ -20 kJ -6.2 kJ -35.5 kJ

Some More Questions From Thermodynamics Chapter

Define an isolated system.

Define intensive properties.

Define extensive properties.

Why all living systems need to be 'open systems'?

Define state variables of a system.

From thermodynamic point of view, to which system the animals and plants belong?

What is a state function?

A thermodynamic state function is a quantity

What is reversible process in thermodynamics?

Define irreversible change.

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

The energy released when 6 moles of octane is burnt in air will be [Given, ΔH_f for CO₂ (g). H₂O(g) and C₈H₁₈ (l), respectively are -490, -240 and +160J/mol]

-37.4 kJ

-20 kJ

-6.2 kJ

-35.5 kJ