## How to distinguish limiting or excess reactant.

George_Zhu
Posts: 29
Joined: Mon Jun 17, 2019 7:23 am

### How to distinguish limiting or excess reactant.

How to distinguish limiting or excess reactant when both reactant has been run out at the same time ?

E.g. c+o2=co2

When it has 1mol carbon atoms and 1mol oxygen molecule, which one is limiting reactant, or it does not have any limiting reactant, and how they should be called?

Chem_Mod
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Joined: Thu Aug 04, 2011 1:53 pm
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### Re: How to distinguish limiting or excess reactant.

If they "both run out at the same time" then there is no limiting or excess reactant. Both reactants were present in the correct ratio.

Haorui Li 1A
Posts: 30
Joined: Mon Jun 17, 2019 7:23 am

### Re: How to distinguish limiting or excess reactant.

Since the chemical equation is balanced, we can see 1 mole of C reacts with 1 mole of O2 to form 1 mole of CO2. The ratio to carbon, oxygen and carbon dioxide are 1:1:1, so if there are 1mol carbon atoms and 1mol oxygen molecules, 1 mol of CO2 will be formed so there will be no limiting reactant. However, if the question gives the mass of reactants, we need to convert them into moles and then compare.

Karina Vasquez 1D
Posts: 35
Joined: Fri Mar 01, 2019 12:15 am

### Re: How to distinguish limiting or excess reactant.

Is there a particular way to find the reactants? Can you write the steps (break them down) to find the limiting reactant please.

Posts: 36
Joined: Tue Feb 12, 2019 12:15 am

### Re: How to distinguish limiting or excess reactant.

The limiting reactant is only when there is little of a certain molecule in the reactant that limits how much there should be in the end product. In this case both sides of the equation are equivalent.

Esha Chawla 3L
Posts: 53
Joined: Thu Jul 25, 2019 12:17 am

### Re: How to distinguish limiting or excess reactant.

This is the way we went over in class to determine how to identify a limiting reactant:
1. Identify the reactants and the products
2. Write a balanced chemical equation
3. Calculate the molar mass of each reactant and product
4. Using the molar mass (from step 3) and the mass of the reactants (should be provided in the question) find the moles of the reactants.
5. Compare the calculated moles to the required moles
-> For example, if the equation is 2H2 (g) + O2 (g) -> 2H20 (l) and you have 3 moles of H2 and 2 moles of O2, H2 is the limiting reactant because it limits the reaction to only occurring one time
6. Based on the moles of limiting reactant, calculate the moles of product that can form.
7. You may have to convert the moles of product to grams based on if the question asks for moles or grams of product.