Question

C(dia ) + O₂ → CO₂ ; ∆H = –395.4 kJ/mole
C(gr ) + O₂ → CO₂ ; ∆H = –393.5 kJ/mole
C(gr ) → C(dia ) ; ∆H = ?
(a) –3.8 (b) –1.9
(c) +3.8 (d) +1.9

Answer 1

answer : option (d) + 1.9

given, C(diamond ) + O₂ → CO₂ ; ∆H = –395.4 kJ/mole

reverse the reaction,

CO₂ ⇒C(diamond) + O₂ ; ∆H = -(-395.4) kJ/mol = 395.4 kJ/mol.......(1)

C(graphite) + O₂ → CO₂ ; ∆H' = –393.5 kJ/mole......(2)

now adding equations (1) and (2) we get,

C(graphite) ⇒C(diamond) ; ∆H" = ∆H' + ∆H

= -393.5 kJ/mol + 395.4 kJ/mol

= +1.9 kJ/mol

hence option (d) is correct choice.

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Answer 2

$\bold{\Delta\,H}$ value of the given reaction is +1.9 kJ/mol

Step by step explanation:

The letter "H" represents the enthalpy of a system.

Enthalpy refers to the sum of a system's internal energy plus the product from the pressure and volume of the system.

The given reactions is as follows.

$C_{(dia)}+O_{2}\rightarrow CO_{2};\Delta\,H=\,-395.4kJ/mol$

$C_{(gr)}+O_{2}\rightarrow CO_{2};\Delta\,H=\,-393.5kJ/mol$

           $\bold{\Delta\,H=C_{(dia)}+O_{2}\rightarrow CO_{2}-C_{(gr)}+O_{2}\rightarrow CO_{2}}$

            $\Delta\,H=-393.5-(-395.4)$

                    $\Rightarrow +1.9\,kJ.mol^{-1}$

Therefore, $\bold{\Delta\,H}$ value of the given reaction is +1.9 kJ/mol

Hence, correct option is "d".

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