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Given that the molar combustion enthalpy of benzene, cyclohexane, and hydrogen are x, y and z, respectively, the molar enthalpy of hydrogenation of benzene to cyclohexane is:
A. x-y+z
B. x-y+3z
C. y-x+z
D. y-x+3z

Last updated date: 19th Jun 2024
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Hint: To answer this you should understand what enthalpy of arrangement and warmth of hydrogenation is: The enthalpy of arrangement is the standard response enthalpy for the development of the compound from its components (ions or atoms) in their most steady reference states at the picked temperature (298.15K) and at 1bar weight. Warmth of hydrogenation of an alkene is the standard enthalpy of synergist hydrogenation of an alkene. Reactant hydrogenation of an alkene is consistently exothermic. Warmth of hydrogenation of alkenes is a proportion of the strength of carbon-carbon two fold bonds.

Complete step by step answer:
Firstly, let us discuss combustion: Ignition is a compound cycle wherein a substance responds quickly with oxygen and emits heat. The first substance is known as the fuel, and the wellspring of oxygen is known as the oxidizer. The fuel can be a strong fluid, or gas, despite the fact that for plane impetus the fuel is normally a fluid.
The ignition of benzene is given as:
\[{C_6}{H_6} + \dfrac{{15}}{2}{O_2} \to 6C{O_2} + 3{H_2}O;\;\;\Delta {H_c}(benzene) = x\; - - - - \left( 1 \right)\]
The ignition of cyclohexane is given as:
\[{C_6}{H_{12}} + 9{O_2} \to 6C{O_2} + 6{H_2}O;\;{\text{ }}\;{H_c}(cyclohexane) = y\; - - - - - \left( 2 \right)\]
The ignition of hydrogen is given as:
\[{H_2} + \dfrac{1}{2}{O_2} \to {H_2}O;\;\;{H_c}(hydrogen) = z\; - - - - - \left( 3 \right)\]
Hydrogenation response of benzene is given as:
\[{C_6}{H_6} + 3{H_2} \to {C_6}{H_{12}}\; - - - - - - \left( 4 \right)\]
From dissecting each of the four conditions we can say that:
\[{H_{hydrogenation}}(benzene) = {H_c}(benzene) + 3 \times {H_c}(hydrogen) - {H_c}(cyclohexane) = x - y + 3z\].

So, the correct answer is Option B.

Note: The warmth of hydrogenation is the measure of warmth delivered during the hydrogenation of an alkene. It relies upon the soundness of the carbon. The less steady for example less subbed carbon will have a higher warmth gracious hydrogenation though the steadier for example more subbed carbon will have less warmth of hydrogenation.