Power of Love

Here is a long (and a little mathsy explanation) of what an order of a reaction is.

The maths here is pretty basic, as long as you understand POWERs (e.g. squaring)  then it is LOVEly. Pretty awful justification of the blog post title. Lets move on.

You know from GCSE (or earlier) that as you increase concentration, rate increases. Greater chance of collision, more succesful collision, blah, blah, blah... You might even have learnt that concentration and rate are directly proportional. 

At A level you learn that both of these facts are only true some of the time. In reality, you will now learn there are three different options (in reality there are more than that but lets not get into that now)

Option A - Some reactants as you increase their concentration, the rate is not changed, these are called zero order reactants. In other words put in as much of it as you want, it ain't going any faster.

Option B - Some reactants as you increase their concentration, the rate increase proportionally (i.e. double conc  = double rate), these are called first order reactants. In other words, pretty much what a GCSE student would've predicted

Option C - Some reactants as you increase their concentration, the rate changes by that number squared (i.e. double conc = quadruple rate, triple conc = 9 times increase in rate etc.) , these are called second order reactants.  In other words more of this stuff really gets reactions going.

You need to understand where these numbers (zero, first, second) come from. These numbers (or orders) are needed as powers in the equations so that they works mathematically

So, (in case you've forgotten) the rate equation is

Rate = k x [Conc].

If it is zero order, that gives us, Rate = k x [Conc]⁰, 

and as anything to the power zero = 1 

that gives us

^{Rate = k x 1 or Rate = k} 

^{in other words, Concentration of the reactant is not in the equation so it doesn't affect rate. (Just like I said in Option A above)}

If it is first order, that gives us, Rate = k x [Conc]¹, 

and as the power 1 doesn't change anything

that gives us

^{Rate = k x [Conc]}  

^{in other words, Concentration of the reactant is directly proportional to rate. (Just like I said in Option B above)}

If it is second order, that gives us, Rate = k x [Conc]², 

^{in other words, If you double Concentration of the reactant the rate goes up by that number squared. So a doubling of a [Conc] would lead to a quadrupling of the rate as 22 = 4. (Just like I said in Option C above)}

So what is the order? 

It is the power, to which you raise the concentration in the rate equation. 

If you read through the whole post, and understand it that last statement is almost pointlessly obvious