Using Molar Ratios

[Nick Smith 2H]

Could someone give an example and//or explain how molar ratios are used in calculating the limiting reactant? Do you multiply the moles of each reactant by their coefficient and then the smaller number is the limiting reactant? Just a little confused, thanks!

[Ayaan_Ekram_2J]

Hello!

When we look at molar ratios for limiting reactants, we will divide the number of moles of a reactant by the coefficient of that molecule or atom to see how many “times” that reaction can be completed. We will then see which number is smaller, so the number that would lead to the fewest number of times the reaction occurs. This corresponds to the limiting reactant. I hope this helps!

[Hayden Jackson]

Hi!

Ok take the equation 2H + O ---> H2O. The coefficients are 2, 1, 1 from left to right. What this means is that in order to make 1 mole of water, you need 2 moles of hydrogen. This is the molar ratio, and they come from the coefficients of the products compared to the reactants. This doesn't mean though that the Oxygen will always been the limiting reactant just because it has a smaller coefficient than hydrogen. Say we have only 1 mole of hydrogen and 3 moles of oxygen, we will only be able to make 1/2 a mole of water because you need at least 2 moles H to make 1 mole water, so hydrogen limits the amount of water we produce, because with 3 moles of oxygen and enough hydrogen we could make 3 moles of water, but we don't have enough hydrogen, so hydrogen would be the limiting reactant. Hope this helps!

[akemiwebster2G]

Divide the number of moles of a reactant by the coefficient of that molecule or atom to see how much the reaction may be completed when looking at molar ratios for limiting reactants. Then see which number is smaller, the number that results in the reaction occurring the fewest number of times. This is the same as the limiting reactant.