If the standard state of sufur is S8 (s), which of the following equations represents the standard enthalpy of formation of H2SO4 (ℓ) ?
A. 2H (g) + S (g) + 4 O (g) H2SO4 (ℓ)
B. H2 (g) + S8 (g) + 2 O2 (g) H2SO4(ℓ)
C. H2SO4 (ℓ) H2 (g) + 1/8 S8 (s) + 2 O2 (g)
D. H2SO4 (ℓ) 2 H (g) + S (s) + 4 O (g)
E. H2 (g) + 1/8 S8 (s ) + 2 O2 (g) H2SO4(ℓ)
To determine the correct equation representing the standard enthalpy of formation of H2SO4 (ℓ), we need to understand what the standard enthalpy of formation is and the conditions under which the reaction occurs.
The standard enthalpy of formation (ΔH°f) is the change in enthalpy that occurs when one mole of a compound is formed from its elements in their standard states (usually taken at 25°C and 1 atm pressure). The standard state of sulfur is S8 (s), which means it exists as a solid composed of eight sulfur atoms bonded together.
Now let's analyze each option:
A. 2H (g) + S (g) + 4 O (g) → H2SO4 (ℓ)
In this equation, sulfur is in gaseous state (S (g)), which is not the standard state. Therefore, option A is incorrect.
B. H2 (g) + S8 (g) + 2 O2 (g) → H2SO4 (ℓ)
In this equation, sulfur is in gaseous state (S8 (g)), which is not the standard state. Therefore, option B is incorrect.
C. H2SO4 (ℓ) → H2 (g) + 1/8 S8 (s) + 2 O2 (g)
This equation does not represent the formation of H2SO4 from its elements. It shows the decomposition of H2SO4 into its elements. Therefore, option C is incorrect.
D. H2SO4 (ℓ) → 2 H (g) + S (s) + 4 O (g)
This equation correctly represents the formation of H2SO4 from its elements. H2SO4 is a liquid (ℓ) and sulfur is in its standard state (S (s)). Therefore, option D is a possible correct answer.
E. H2 (g) + 1/8 S8 (s) + 2 O2 (g) → H2SO4 (ℓ)
In this equation, sulfur is in solid state (S8 (s)), which is the standard state of sulfur. Therefore, option E is a possible correct answer.
Based on the analysis, the correct equation representing the standard enthalpy of formation of H2SO4 (ℓ) can be either option D or option E.