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Rate of Reaction and Rate Law
For most equations you can write a rate law in the form of $r = k[X]^m[Y]^n$, where r is the rate of appearance of a product compound, $X$ and $Y$ being the reactant compounds, $k$ being the rate constant, and $m$ and $n$ being the order of the reactants.
This rate law equation allows you to make guesses on the reaction rate based off a $k$ value (given or calculated) alongside quantities of $X$ and $Y$.
Finding Orders
Take the example diagram here for the reaction $2NO_{(g)} + 2H_{2 (g)} -> N_{2 (g)} + 2H_2O_{(g)}$. To determine $m$ and $n$ for the rate law, you have to find pairs of trials that only modify 1 of the reactant compound's quantity, divide it, and compare the quotient to the reaction rate's quotient1). Refer to the table below for the corresponding order.
