When 3.05 moles of ch4 are mixed with 5.03 moles of 02 the limiting reactant is?

To determine the limiting reactant of a reaction, it is important first to know the balanced reaction. For this case, it is:

CH4 + 2O2 = CO2 + 2H2O

We determine as follows:

3.05 mol CH4 (2 mol O2 / 1 mol CH4)= 6.1 mol O2 needed 
5.03 mol O2 (1 mol CH4 / 2 mol O2 )= 2.515 mol CH4 needed

Since the needed amount of CH4 is less than what is given, the O2 should be the limiting reactant since it would react completely.

It's not the same dearthe first one is in grams per mole while the other is not

It's a