Chapter 2: Q12.6 45P (page 36)

The standard enthalpy change of combustion [to $C O_{2} (g) a n d H_{2} O (l)$ at 25⁰ Cof the organic liquid cyclohexane, C₆H₁₂(l), is -3731.7kJmol^-1. Determine the $Δ H_{f}^{0}$ of C₆H₁₂(l).

Short Answer

Expert verified

The standard enthalpy value of the reactant $(Δ H_{f}^{°}) o f C_{6} H_{12} i s - 58.86 k J / m o l$

Step by step solution

Given data

$Δ H^{\circ}$ (Standard enthalpy change) value of Cyclohexane) C₆H₁₂(l) is -3731.7kJmol^-1.

$C_{6} H_{1} 0 (l) + 17 / 2 O_{2} (g) \to 6 C O_{2} (g) + 5 H_{2} O (l) .$

Concept of Enthalpy

Enthalpy change is amount of heat absorbed or evolved in a reaction when carried out at a constant pressure. It is generally calculated as the difference in energy required for bond breaking in a chemical reaction and energy gained in forming new bonds in a chemical reaction.

It is represented by $Δ H$ .

Calculate the value of ΔHf° of C6H12

The enthalpy change is calculated as:

$Δ H^{°} = n Δ H_{f}^{o} (P r o d u c t s) - n Δ H_{f}^{o} (R e a c t a n t s)$ ...... (1)

Where, $Δ H_{f}^{o}$ represent the standard enthalpy value.

localid="1663737494734" $Δ H_{f}^{o} o f O_{2} i s 0 .$

$Δ H_{f}^{o} o f H_{2} O i s - 285.83 k J m o l^{- 1} .$

$Δ H_{f}^{o} o f C O_{2} i s - 393.51 k J m o l^{- 1}$

$Δ H^{°} = - 3731.7 k J m o l^{- 1}$

The given expression is localid="1663738633260" $C_{6} H_{1} 0 (l) + 17 / 2 O_{2} (g) \to 6 C O_{2} (g) + 5 H_{2} O (l) .$

Substitute these values in equation (1).

$Δ H^{\circ} = 6 Δ H_{f}^{0} [C O_{2} (g)] + 5 Δ H_{f}^{0} [H_{2} O (l)] - {Δ H_{f}^{a} [C_{6} H_{10} (l)] + \frac{17}{2} \times Δ H_{f}^{0} [O_{2} (g)]}$

$- 3731.7 k J m o l^{- 1} = 6 \times (- 393.51 k J m o l^{- 1}) + 5 \times (- 285.83 k J m o l^{- 1}) - {Δ H_{f}^{a} [C_{6} H_{10} (l)] + 17 / 2 \times 0]} Δ H_{f}^{a} [C_{6} H_{10} (l)] = - 2361.06 k J m o l^{- 1} - 1429.5 k J m o l^{- 1} + 3731.7 k J m o {l^{- 1}}^{}$

Therefore, $= - 58.86 \frac{k]}{m o l}$ .

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The standard enthalpy change of combustion [to $C O_{2} (g) a n d H_{2} O (l)$ at 25⁰ Cof the organic liquid cyclohexane, C₆H₁₂(l), is -3731.7kJmol^-1. Determine the $Δ H_{f}^{0}$ of C₆H₁₂(l).

Short Answer

Step by step solution

Given data

Concept of Enthalpy

Calculate the value of ΔHf° of C6H12

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The standard enthalpy change of combustion [to CO2(g)andH2O(l)at 250 Cof the organic liquid cyclohexane, C6H12(l), is -3731.7kJmol-1. Determine the ΔHf0of C6H12(l).

Short Answer

Step by step solution

Given data

Concept of Enthalpy

Calculate the value of ΔHf° of C6H12

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Chemistry Textbooks

Physical Chemistry

Ionic and Molecular Compounds

Chemical Reactions

The Earths Atmosphere

Organic Chemistry

Kinetics

Study anywhere. Anytime. Across all devices.

The standard enthalpy change of combustion [to $C O_{2} (g) a n d H_{2} O (l)$ at 25⁰ Cof the organic liquid cyclohexane, C₆H₁₂(l), is -3731.7kJmol^-1. Determine the $Δ H_{f}^{0}$ of C₆H₁₂(l).