Determine which of the following reactions has the smallest orientation factor which uses the variable P. Now remember when it comes to the orientation factor, we say that the larger the reactant molecules then the smaller your orientation factor will be.
So if we take a look here in A our reactant molecules are just this iodine and then HI. For B it's just two hydrogens. Now for sure this is out because hydrogens are the smallest element. So this one will be expected to have a very high orientation factor.
For C we have BR2 with this molecule which is called ethene and here we're not concerned with the products being formed. Again, we're looking at the size of the reacting molecules, so our reactants and if we take a look here, we know that these also out because the reactants are not all the same size, so they wouldn't have the same orientation factor values.
The answer here is option C because BR2 and ethene are definitely larger in size than just an iodine by itself. And HI. So here for C those two reacting molecules are the largest. This will result in smaller orientation factors which could result in an unsuccessful collision later down the road, so you might be less likely to form the product here as a result.
So keep this in mind when we're talking about the orientation factor. Larger reactants equals smaller orientation factor.