Stoichiometry: limiting reagent, mass of product and percentage yield
Choose a balanced equation and the amounts of the two reactants and see which one is used up first, how much product forms, how much reactant is left over and the percentage yield. Free for every student.
Also searched as: stoichiometry class 11 · stoichiometry class 11 · limiting reagent · balanced equation mole ratio · percentage yield · theoretical yield
About this experiment
| Subject | Chemistry |
|---|---|
| Class | 11 |
| Unit | 1. Some Basic Concepts of Chemistry |
| NCERT section | 1.9–1.10 |
| Level | NCERT level |
| Time | about 20 minutes |
| Access | Free, no card needed |
Aim
To use the mole ratio of a balanced equation to find the limiting reagent, the amount of product formed, the excess reactant left and the percentage yield.
Theory
A balanced chemical equation tells us the mole ratio in which substances react: in N₂ + 3H₂ → 2NH₃, 1 mol of N₂ reacts with 3 mol of H₂ and gives 2 mol of NH₃. The total mass of reactants equals the total mass of products (law of conservation of mass).
Reactants are rarely mixed in exactly the right ratio. The reactant that is used up first is the limiting reagent and it decides how much product can form. The other reactant is in excess and some of it is left over. To find the limiting reagent, divide the moles of each reactant by its coefficient: the smaller number belongs to the limiting reagent.
The theoretical yield is the amount of product calculated from the limiting reagent. The actual yield is what is really obtained, and the percentage yield is (actual yield / theoretical yield) × 100.
Formulas used
- extent of reaction ξ = n(reactant) / coefficient, the smallest value is the limit
- n(product) = coefficient × ξ
- mass = moles × molar mass
- percentage yield = (actual yield / theoretical yield) × 100
- excess left = initial − coefficient × ξ
Procedure: what to do in the virtual lab
- Choose N₂ + 3H₂ → 2NH₃ with 2 mol N₂ and 3 mol H₂. Find the limiting reagent.
- Increase H₂ to 6 mol. What is the limiting reagent now and how much NH₃ forms?
- Set the percentage yield to 70 % and compare the actual with the theoretical yield.
- Check that the total mass before the reaction equals the total mass after it (at 100 % yield).
Observations to make
- The reactant with the smaller ratio n / coefficient is used up first, whatever its number of moles.
- More of the excess reactant does not give more product.
- The mass before and after the reaction is always the same.
What you can change in this experiment
- Reaction: 2 H₂ + O₂ → 2 H₂O / N₂ + 3 H₂ → 2 NH₃ (Haber process) / CH₄ + 2 O₂ → CO₂ + 2 H₂O / 2 Mg + O₂ → 2 MgO
- Amount of the first reactant A (mol)
- Amount of the second reactant B (mol)
- Percentage yield of the reaction (%)
Viva questions on Stoichiometry
Questions an examiner may ask in the Class 11 chemistry practical. Run the experiment in the lab to find the answers yourself, then check them in the Learn tab.
- What is a limiting reagent?
- How do you find it from a balanced equation?
- What is percentage yield?
- What does a balanced equation say about the mass of reactants and products?
Frequently asked questions
What is the aim of the Stoichiometry experiment?
To use the mole ratio of a balanced equation to find the limiting reagent, the amount of product formed, the excess reactant left and the percentage yield.
Which formulas are used in the Stoichiometry experiment?
extent of reaction ξ = n(reactant) / coefficient, the smallest value is the limit; n(product) = coefficient × ξ; mass = moles × molar mass; percentage yield = (actual yield / theoretical yield) × 100; excess left = initial − coefficient × ξ
What viva questions are asked on Stoichiometry?
What is a limiting reagent? How do you find it from a balanced equation? What is percentage yield? What does a balanced equation say about the mass of reactants and products?
How do I do the stoichiometry class 11 experiment for Class 11 online?
Open the Stoichiometry virtual lab on PractiSci, follow the procedure above, change the values and read the live graph. It matches the Class 11 chemistry practical, with the aim, theory, observations and viva questions on this page.
Can I do the Stoichiometry experiment online?
Yes. Open it as a 3D virtual lab in your browser or on your phone, change the values and read the results from live graphs. This lab is free.
Syllabus: Class XI Chemistry, Chapter 1 — Some Basic Concepts of Chemistry, §1.9 (stoichiometry and stoichiometric calculations), limiting reagent
What you do in the lab
Change the controls and watch the chemistry behave in real time in 3D. Live readouts and graphs show the numbers behind it, and the Learn tab has the theory, procedure, observations and viva questions. Works on a phone or a laptop, in English and Hindi.
Topics: stoichiometry · limiting reagent · balanced equation · percentage yield · mole ratio · theoretical yield · some basic concepts of chemistry
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