Jason combines the two intermediate steps shown.
$\begin{array}{l}
N_2(g)+O_2(g) \longrightarrow 2 NO(g) \\
2 NO(g)+O_2(g) \longrightarrow 2 NO_2(g)
\end{array}$
Which best describes what Jason should do with the oxygen molecules?
A. Place two of them as products.
B. Place two of them as reactants.
C. Cancel them out because there is one in each equation.
D. Double them because there is one in each equation.
Answer (1)
Combine the two given chemical equations.
Cancel out any common terms on both sides of the equation.
Combine the oxygen molecules on the reactant side.
Conclude that two oxygen molecules should be placed as reactants: Pl a ce tw oo f t h e ma sre a c t an t s .
Explanation
Analyze the Chemical Equations We are given two chemical equations that Jason combines:
N 2 ( g ) + O 2 ( g ) ⟶ 2 NO ( g )
2 NO ( g ) + O 2 ( g ) ⟶ 2 N O 2 ( g )
We need to determine what happens to the oxygen molecules when these two equations are combined.
Combine the Equations To combine the equations, we add the reactants and products together:
N 2 ( g ) + O 2 ( g ) + 2 NO ( g ) + O 2 ( g ) ⟶ 2 NO ( g ) + 2 N O 2 ( g )
Cancel Common Terms Now, we simplify the equation by canceling out any common terms on both sides. In this case, 2 NO ( g ) appears on both sides, so we can cancel it out:
N 2 ( g ) + O 2 ( g ) + O 2 ( g ) ⟶ 2 N O 2 ( g )
Combine Oxygen Molecules Combine the oxygen molecules on the reactant side:
N 2 ( g ) + 2 O 2 ( g ) ⟶ 2 N O 2 ( g )
Conclusion From the combined equation, we see that there are two oxygen molecules ( 2 O 2 ( g ) ) on the reactant side and none on the product side. Therefore, Jason should place two oxygen molecules as reactants.
Examples
In chemical reactions, understanding how to combine and simplify equations is crucial for predicting the outcome of a reaction. For example, if you're trying to synthesize a particular compound, you need to know the exact amount of each reactant required. By correctly combining intermediate steps, you can determine the overall reaction and the necessary quantities of reactants, ensuring efficient and successful synthesis.
