The enthalpy of combustions at 25^∘ C of II2, cyclohexene (C6 II10) and cyclohexane (C6 II12) ar

Name: Problem 44, Chapter 6: Objective Chemistry for Engineering and Medical Entrance Examinations
Uploaded: 2022-01-25T13:36:50-08:00
Duration: 59 s
Channel: Mishal Gul
Description: The enthalpy of combustions at 25^∘ C of II2, cyclohexene (C6 II10) and cyclohexane (C6 II12) arc 241 , 3800 and 3920 kJ / mol, respectively. The heat of hydrogenation of cyclohexane is(1) -121 kJ / mole (2)+121 kJ / mole (3) -242 kJ / mole (4) +242 kJ / mol

step 1 The enthalpy of combustion at 25 degrees Celsius of hydrogen, cyclohexene and cyclohexane are 24

Question

The enthalpy of combustions at $25^{\circ} \mathrm{C}$ of $\mathrm{II}_{2}$, cyclohexene $\left(\mathrm{C}_{6} \mathrm{II}_{10}\right)$ and cyclohexane $\left(\mathrm{C}_{6} \mathrm{II}_{12}\right)$ arc 241 , 3800 and $3920 \mathrm{~kJ} / \mathrm{mol}$, respectively. The heat of hydrogenation of cyclohexane is(1) $-121 \mathrm{~kJ} / \mathrm{mole}$ $(2)+121 \mathrm{~kJ} / \mathrm{mole}$ (3) $-242 \mathrm{~kJ} / \mathrm{mole}$ (4) $+242 \mathrm{~kJ} / \mathrm{mol}$

   The enthalpy of combustions at $25^{\circ} \mathrm{C}$ of $\mathrm{II}_{2}$, cyclohexene $\left(\mathrm{C}_{6} \mathrm{II}_{10}\right)$ and cyclohexane $\left(\mathrm{C}_{6} \mathrm{II}_{12}\right)$ arc 241 , 3800 and $3920 \mathrm{~kJ} / \mathrm{mol}$, respectively. The heat of hydrogenation of cyclohexane is(1) $-121 \mathrm{~kJ} / \mathrm{mole}$
$(2)+121 \mathrm{~kJ} / \mathrm{mole}$
(3) $-242 \mathrm{~kJ} / \mathrm{mole}$
(4) $+242 \mathrm{~kJ} / \mathrm{mol}$

Objective Chemistry for Engineering and Medical Entrance Examinations

K Rama Rao 1st Edition

Chapter 6, Problem 44

Instant Answer

Solved by Expert Mishal Gul

01/25/2022

Step 1

Step 1: The heat of hydrogenation of cyclohexene to cyclohexane can be calculated using Hess's law, which states that the total enthalpy change for a reaction is the same whether it occurs in one step or in a series of steps. Show more…

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The enthalpy of combustions at $25^{\circ} \mathrm{C}$ of $\mathrm{II}_{2}$, cyclohexene $\left(\mathrm{C}_{6} \mathrm{II}_{10}\right)$ and cyclohexane $\left(\mathrm{C}_{6} \mathrm{II}_{12}\right)$ arc 241 , 3800 and $3920 \mathrm{~kJ} / \mathrm{mol}$, respectively. The heat of hydrogenation of cyclohexane is(1) $-121 \mathrm{~kJ} / \mathrm{mole}$ $(2)+121 \mathrm{~kJ} / \mathrm{mole}$ (3) $-242 \mathrm{~kJ} / \mathrm{mole}$ (4) $+242 \mathrm{~kJ} / \mathrm{mol}$

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Key Concepts

Heat of Hydrogenation

This refers to the energy change when a molecule with unsaturation, such as a double bond, is reacted with hydrogen to form a saturated compound. It is typically an exothermic process and provides insight into the degree of stabilization afforded by the unsaturated bond as well as the stability of the compound.

Hess’s Law

Hess’s Law states that the total enthalpy change in a chemical reaction is independent of the pathway taken. This principle allows for the calculation of an unknown enthalpy change (such as hydrogenation energy) by combining known enthalpies from related reactions into a thermochemical cycle.

Enthalpy of Combustion

This is the amount of heat released when one mole of a substance is completely burned in oxygen under standard conditions. It reflects the total energy content of the compound and is used to compare the relative stabilities of different substances and the energies of chemical bonds present within them.

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