To understand what Jason should do with the oxygen molecules, let’s first look at the two intermediate steps of the chemical reactions:
1. [tex]\( N_2(g) + O_2(g) \longrightarrow 2 NO(g) \)[/tex]
2. [tex]\( 2 NO(g) + O_2(g) \longrightarrow 2 NO_2(g) \)[/tex]
When combining two chemical equations, it’s important to look at the common substances on both sides and determine how they interact. Here's what happens step-by-step:
1. In the first reaction:
- Reactants: [tex]\( N_2(g) \)[/tex] and [tex]\( O_2(g) \)[/tex]
- Products: [tex]\( 2 NO(g) \)[/tex]
2. In the second reaction:
- Reactants: [tex]\( 2 NO(g) \)[/tex] and [tex]\( O_2(g) \)[/tex]
- Products: [tex]\( 2 NO_2(g) \)[/tex]
Notice that:
- The product [tex]\( 2 NO(g) \)[/tex] from the first reaction is the reactant in the second reaction.
Now, let's analyze the oxygen molecules:
- The first reaction uses 1 molecule of [tex]\( O_2 \)[/tex].
- The second reaction uses another molecule of [tex]\( O_2 \)[/tex].
These [tex]\( O_2 \)[/tex] molecules appear as reactants in both reactions, but there isn’t any [tex]\( O_2 \)[/tex] appearing in the final product side of either reaction.
To combine the whole process into a single overall reaction without the intermediate substances (if possible), you should:
1. Add the first reaction and the second reaction together:
[tex]\[
\begin{array}{c}
N_2(g) + O_2(g) \longrightarrow 2 NO(g) \\
+ \\
2 NO(g) + O_2(g) \longrightarrow 2 NO_2(g)
\end{array}
\][/tex]
Combining them:
[tex]\[
N_2(g) + O_2(g) + 2 NO(g) + O_2(g) \longrightarrow 2 NO(g) + 2 NO_2(g)
\][/tex]
2. Notice that [tex]\( 2 NO(g) \)[/tex] on the reactant side and [tex]\( 2 NO(g) \)[/tex] on the product side can be canceled out. This simplifies the equation to:
[tex]\[
N_2(g) + O_2(g) + O_2(g) \longrightarrow 2 NO_2(g)
\][/tex]
3. Combine the oxygen molecules:
[tex]\[
N_2(g) + 2 O_2(g) \longrightarrow 2 NO_2(g)
\][/tex]
In this case, you realize that the oxygen molecules balance out naturally, and there isn't any oxygen residue left on their own in the final reaction. However, the original equations said there was one oxygen molecule in each intermediate step, and thus, they cancel each other out to reach the final equation.
Therefore, the best description is:
Cancel them out because there is one in each equation.
