# I don't know how to approach this question? I need help

Aug 10, 2018

$\textsf{\text{d} .}$ "Rate" = k["SO"_2]["H"_2]

#### Explanation:

The question is asking for the order of the reaction about each reactant given data from the table supplies the following correlations:

• Doubling $\left[{\text{SO}}_{2}\right]$ while holding $\left[{\text{H}}_{2}\right]$ constant doubles $\text{Rate}$;
• Holding $\left[{\text{H}}_{2}\right]$ constant while doubling $\left[{\text{SO}}_{2}\right]$ doubles $\text{Rate}$.

Where $\left[{\text{SO}}_{2}\right]$ and $\left[{\text{H}}_{2}\right]$ represent the concentration of the two respective species, as your chemistry teacher has likely mentioned during classes.

Now back to the question: the key is to find an exponential relationship that properly satisfies all (or both, as in this question) arithmetic correlations the question has implied. For this particular case:

• ${1}^{\textcolor{n a v y}{1}} \times {1}^{\textcolor{n a v y}{1}} = 1$
• ${2}^{\textcolor{n a v y}{1}} \times {1}^{\textcolor{n a v y}{1}} = 2$
• ${2}^{\textcolor{n a v y}{1}} \times {2}^{\textcolor{n a v y}{1}} = 4$

The exponent $\textcolor{n a v y}{1}$ is typically omitted in many expressions. Thus the rate law for this reaction given these data would be

"Rate" = k["SO"_2]^color(navy)(1) ["H"_2]^color(navy)(1)

... where $k$ the rate constant unique to this reaction and dependent on temperature.

As a side note, the cardinal number that corresponds to the exponent of a particular reactant identifies the order of that species in the reaction, for instance

• A reaction is of "zero" order about a reactant with exponent $0$ omitted (or in other words included as part of the constant $k$) in the rate law expression
• A reaction is of "first" order about a reactant with exponent $1$, as in this case for both reactants
• A reaction is of "second" order about a reactant with exponent $2$

Reactions of orders higher than two are rare given the unlikelihood for three microscopic particles to collide simultaneously.