C(dianemd) +O2( g) →CO2( g) ; ΔH=395 kJ C(Braphite) +O2( g) →CO2( g) ; Δ/ I=-393.5 kJ The Δ/ /

step 1 Carbon, that is diamond plus oxygen gas, forms carbon dioxide, heat of enthalpy is 395 kilojoult

C(dianemd) +O2( g) →CO2( g) ; ΔH=395 kJ C(Braphite) +O2( g)...

$C_{\text {(dianemd) }}+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g}) ; \Delta H=395 \mathrm{~kJ}$ $C_{\text {(Braphite) }}+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g}) ; \Delta / I=-393.5 \mathrm{~kJ}$ The $\Delta / /$ when diamond is formed from graphite (1) $-1.5 \mathrm{~kJ}$ $(2)+1.5 \mathrm{~kJ}$ (3) $+3.0 \mathrm{k} \mathrm{J}$ (4) $-3.0 \mathrm{~kJ}$

$C_{\text {(dianemd) }}+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g}) ; \Delta H=395 \mathrm{~kJ}$
$C_{\text {(Braphite) }}+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g}) ; \Delta / I=-393.5 \mathrm{~kJ}$
The $\Delta / /$ when diamond is formed from graphite
(1) $-1.5 \mathrm{~kJ}$
$(2)+1.5 \mathrm{~kJ}$
(3) $+3.0 \mathrm{k} \mathrm{J}$
(4) $-3.0 \mathrm{~kJ}$

Key Concepts

Standard Enthalpy of Formation

The standard enthalpy of formation is the enthalpy change that occurs when one mole of a compound is formed from its elements in their standard states. For elements like carbon, different allotropes (e.g., graphite and diamond) have distinct standard enthalpies of formation, reflecting their relative stabilities.

Hess's Law

Hess's Law states that the total enthalpy change for a reaction is the same regardless of the pathway taken, which allows us to relate different reactions by algebraically combining their enthalpy changes. In the context of the problem, this principle is used to determine the energy difference between two forms of carbon by comparing their combustion reactions.

Allotropes

Allotropes refer to different structural forms of the same element, such as graphite and diamond for carbon. These allotropes have different physical properties and energies, which is critical when analyzing reactions involving these forms due to the energy differences associated with their formation.

Energy Differences between Allotropes

The variation in combustion energies between graphite and diamond reflects the inherent energy difference between these two allotropes. The difference in enthalpy between their combustion reactions can be used to determine the enthalpy change for converting one allotrope to another, which in this problem indicates the energy required to form diamond from graphite.

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