## Limiting Reactants

Ariana Morales
Posts: 29
Joined: Fri Sep 28, 2018 12:15 am

### Limiting Reactants

How do we know which one is the limiting reactant? The one with the greatest or least mass?

Posts: 33
Joined: Fri Sep 28, 2018 12:18 am

### Re: Limiting Reactants

Limiting reactant is the reactant with the least amount of mol produced.

Sara Lakamsani 4D
Posts: 61
Joined: Fri Sep 28, 2018 12:29 am

### Re: Limiting Reactants

To find the limiting reactant, you need to compare the moles of each reactant, not the masses. To start, make sure you have balanced equation to represent the reaction. This will tell you the molar ratio in which the compounds react with each other. For example, if you have $4NH_{3}+5O_{2}\rightarrow 4NO+6H_{2}O$, then you know that you need $NH_{3}$ and $O_{2}$ in a proportion of 4:5. If you are given the masses of each reactant, then you can convert these amounts to moles by dividing by their molar masses. Then you compare the moles you have to the moles needed. For this reaction, if you had 3 mol $NH_{3}$ and 5 mol $O_{2}$, $NH_{3}$ would be the limiting reactant, because the reaction require 4 mol $NH_{3}$ to use up all 5 mol $O_{2}$. In other words, there will be $O_{2}$ left over once all the $NH_{3}$ has been used in the reaction

Alex Alonso - 4F
Posts: 28
Joined: Fri Sep 28, 2018 12:27 am

### Re: Limiting Reactants

It's the one with the least mass after converting to calculated moles and the required moles. The limiting reactant is completely consumed in the reaction and "limits" how much product is formed.

Brian Chhoy 4I
Posts: 66
Joined: Fri Sep 28, 2018 12:16 am

### Re: Limiting Reactants

The post above is correct, but there are multiple ways to approach these types of problems. The method I usually use is to take to given masses of the reactants and convert them to moles of reactants. Followed by using the mole ratio and converting that to the total moles of the product that can be produced. Do this to all the reactants. The reactant that leads to the least amount of the product being produced is the limiting reactant.

Kailey Nichols 4B
Posts: 30
Joined: Fri Sep 28, 2018 12:28 am

### Re: Limiting Reactants

When looking for the limiting reactant, you should actually look at the moles and the ratio of the moles rather than the mass. Looking at the mass can be misleading because elements vary in mass.

For example, if you given 13g of CH4 and 30g of O2 for the chemical reaction:
CH4 + 2O2 --> CO2 + 2H2O
O2 would actually be the limiting reactant (even though you're given a greater mass of it) because the molar ratio for these reactants is 1 CH4 : 2 O2 and by when you calculate the moles of each reactant by using the mass that is given, you would get about 1 mole of CH4 and 1.9 moles of O2 which when compared to the 1 CH4 : 2 O2 ratio of the reactants in the chemical reaction make O2 the limiting reactant.

Jack Mitchell 3J
Posts: 24
Joined: Fri Sep 28, 2018 12:24 am

### Re: Limiting Reactants

If you were to do the whole problem as many time as the amount of reactants, each assuming a different reactant to be the limiting reactant, the answer that produces the least product is the limiting reactant.