Question

consider the following intermediate chemical equations.
c(s) + \frac{1}{2}o_2(g) \
ightarrow co(g)
co(g) + \frac{1}{2}o_2(g) \
ightarrow co_2(g)
when you form the final chemical equation, what should you do with co?
\bigcirc cancel out co because it appears as a reactant in one intermediate reaction and a product in the other intermediate reaction.
\bigcirc add the two co molecules together, and write them as reactants in the final chemical reaction.
\bigcirc write co only once as a reactant in the final chemical reaction.
\bigcirc write co as a reactant and a product in the final chemical reaction.

Explanation:

To determine what to do with \( \text{CO} \) when combining the intermediate equations, we analyze the two reactions:

1. \( \text{C}(s) + \frac{1}{2}\text{O}_2(g)

ightarrow \text{CO}(g) \) (CO is a product here).

1. \( \text{CO}(g) + \frac{1}{2}\text{O}_2(g)

ightarrow \text{CO}_2(g) \) (CO is a reactant here).

In Hess's Law (used for combining chemical equations), species that appear as a product in one reaction and a reactant in another (with the same stoichiometry) are canceled out (they are intermediates).

Now, evaluate the options:

• "Cancel out CO because it appears as a reactant in one intermediate reaction and a product in the other intermediate reaction." → Matches the analysis (CO is product in first, reactant in second; cancelable).
• "Add the two CO molecules together..." → Incorrect (CO is not added; it is an intermediate to cancel).
• "Write CO only once as a reactant..." → Incorrect (CO is not a net reactant/product).
• "Write CO as a reactant and a product..." → Incorrect (Intermediates are canceled, not retained).

Answer:

A. Cancel out CO because it appears as a reactant in one intermediate reaction and a product in the other intermediate reaction.