Question

which of the following represents a formation equation for $\ce{c6h12o6(s)}$?
\bigcirc $\ce{6 c(g) + 12 h2(g) + 6 o2(g) -> c6h12o6(s)}$
\bigcirc $\ce{c6h12o6(s) -> 6 c(g) + 6 h2(g) + 3 o2(g)}$
\bigcirc $\ce{6 c(s) + 6 h2(g) + 3/2 o2(g) -> c6h12o6(s)}$
\bigcirc $\ce{6 c(g) + 6 h2(g) + 3 o2(g) -> c6h12o6(s)}$

Explanation:

Step1: Recall Formation Reaction Definition

A formation reaction is one where 1 mole of a compound is formed from its constituent elements in their standard states. The standard state of carbon is solid (C(s)), hydrogen is gas (H₂(g)), and oxygen is gas (O₂(g)).

Step2: Analyze Each Option

• First Option: Reactants are C(g), H₂(g), O₂(g). Carbon's standard state is solid, not gas. Eliminate.
• Second Option: Reactants are C(s), H₂(g), O₂(g) (with O₂ as 3/2 O₂ to balance O). Product is 1 mole of C₆H₁₂O₆(s). This uses elements in standard states to form 1 mole of the compound.
• Third Option: This is a decomposition (reverse of formation), not formation. Eliminate.
• Fourth Option: Reactants form the compound, but carbon is in gaseous state (non - standard) and stoichiometry for O₂ is 3, but the reactant states for C are incorrect. Also, the reaction is forming from non - standard C state. Eliminate.

Answer:

6 C(s) + 6 H₂(g) + 3/2 O₂(g) ⟶ C₆H₁₂O₆(s) (the second option in the list)