What's the limiting reactant in the reaction between Ba2NO3 and H2SO4 and how do i determine it?

First you write the reaction, then you see which reactant is present in the least amount (moles). So you have Ba(NO3)2 + H2SO4 --> BaSO4 + 2HNO3. The problem will tell you how many grams of each reactant there is. Then you calculate moles of each, and since the ratio is 1:1 you can see which is present in the least, or liminitng amount.