Undergraduate
  1. General chemistry  1.1. Introduction to Chemistry  1.2. Atomic Structure  1.2.1. Subatomic particles  1.2.2. Atomic Model  1.2.3. Quantum numbers  1.2.4. Electron Configuration  1.2.5. Periodic trends  1.2.6. Isotopes and their applications  1.3. Chemical bond  1.3.1. Ionic bond  1.3.2. Covalent bonds  1.3.3. Metal Bond  1.3.4. Hybridization  1.3.5. Molecular geometry and VSEPR theory  1.3.6. Bond polarity and dipole moment  1.4. Stoichiometry  1.4.1. Mole concept  1.4.2. Empirical and molecular formula  1.4.3. Limiting reactant and excess reactant  1.4.4. Percent Yield and Purity  1.4.5. Dilution calculation  1.5. States of matter  1.5.1. Gas Laws  1.5.2. Matter and Intermolecular Forces  1.5.3. Solid and Crystal Structures  1.5.4. Phase diagram  1.5.5. Plasma and supercritical fluid  1.6. Chemical reactions  1.6.1. Types of Chemical Reactions  1.6.2. Balancing Chemical Equations  1.6.3. Thermochemical reactions  1.6.4. Reaction energy profiles  1.7. Solutions and Mixtures  1.7.1. Concentration units  1.7.2. Syndrome properties  1.7.3. Solubility and Solubility Rules  1.7.4. Henry's Law and Raoult's Law  1.7.5. Partition coefficient  1.8. Chemical equilibrium  1.8.1. Law of mass action  1.8.2. Le Chatelier's principle  1.8.3. Reaction quotient  1.8.4. To use this online calculator for Equilibrium Constant, enter Equilibrium Constant (Eq.) and hit the calculate button. Here is how the Equilibrium Constant calculation can be explained with given input values -> 0.05 = 0.05/0.  1.8.5. Acid-base balance  1.9. Acids and bases  1.9.1. Arrhenius, Brønsted–Lowry, and Lewis definitions  1.9.2. pH and pOH  1.9.3. Acid-base titration  1.9.4. Buffer Solution  1.9.5. Acid-base indicator  1.9.6. Polyprotic Acids and Bases  1.10. Electrochemistry  1.10.1. redox reactions  1.10.2. Galvanic and Electrolytic Cells  1.10.3. Nernst equation  1.10.4. Electrolysis  1.10.5. Faraday's laws of electrolysis  1.11. Thermodynamics  1.11.1. Laws of Thermodynamics  1.11.2. Enthalpy, entropy and Gibbs free energy  1.11.3. Spontaneity of reactions  1.11.4. Thermodynamic cycles (Hess's law, Carnot cycle)  1.12. Kinetics  1.12.1. Rate law and reaction order  1.12.2. Activation Energy and Catalyst  1.12.3. Collision theory  1.12.4. Reaction mechanism  1.12.5. Transition state theory
  2. Organic chemistry  2.1. Structure and relationships  2.1.1. Hybridisation in Carbon Compounds  2.1.2. Resonance and aromatization  2.1.3. Molecular orbitals  2.1.4. Inductive and mesomeric effects  2.2. Hydrocarbons  2.2.1. Hydrocarbons  2.2.2. Alkene  2.2.3. Alkynes  2.2.4. Aromatic compounds  2.2.5. Cycloalkanes and Conformation  2.3. Functional Group  2.3.1. Alcohols and phenols  2.3.2. Ethers and epoxides  2.3.3. Aldehyde and ketone  2.3.4. Carboxylic acids and derivatives  2.3.5. Amin  2.3.6. Esters and amides  2.3.7. Thiols and sulfides  2.4. Stereoscopic  2.4.1. Isomerism in Stereochemistry  2.4.2. Chirality and optical activity  2.4.3. Structural analysis  2.4.4. Diastereomers and Enantiomers  2.5.1. Substitution reactions  2.5.2. Elimination reactions  2.5.3. Addition reactions  2.5.4. Radical reactions  2.5.5. Rearrangement reactions  2.5.6. Pericyclic Reactions  2.6. Spectroscopy and structural analysis  2.6.1. Infrared Spectroscopy  2.6.2. Nuclear magnetic resonance spectroscopy  2.6.3. Mass Spectrometry  2.6.4. UV-visible spectroscopy  2.6.5. X-ray crystallography  2.7. Polymer chemistry  2.7.1. Addition and Condensation Polymers  2.7.2. Polymerization mechanism  2.7.3. Biodegradable Polymer  2.7.4. Conducting and smart polymers
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Ligands and coordination compounds  3.1.2. Crystal field theory  3.1.3. Molecular Orbital Theory in Coordination Compounds  3.1.4. Jahn–Taylor distortion  3.2. Main Group Chemistry  3.2.1. Alkali and alkaline earth metals  3.2.2. Halogens and Noble Gases  3.2.3. Transition metals and their complexes  3.2.4. Lanthanides and Actinides  3.3. Solid state chemistry  3.3.1. Crystal lattices and unit cells  3.3.2. Defects in solids  3.3.3. Electrical and magnetic properties  3.3.4. Superconductivity  3.4. Bio-inorganic chemistry  3.4.1. Metal ions in biology  3.4.2. Enzymatic reactions with metals  3.4.3. Metal poisoning and detoxification  3.4.4. Metalloproteins and Metalloenzymes
  4. Physical chemistry  4.1. Quantum Chemistry  4.1.1. Wave–particle duality  4.1.2. Schrödinger Equation  4.1.3. Quantum Numbers and Orbitals  4.1.4. Atomic and molecular spectroscopy  4.2. Statistical mechanics  4.2.1. Maxwell–Boltzmann distribution  4.2.2. Partitioning functions  4.2.3. Bose–Einstein and Fermi–Dirac statistics  4.3. Chemical thermodynamics  4.3.1. Gibbs Free Energy  4.3.2. Phase transition  4.3.3. Thermodynamic efficiency  4.4. Surface chemistry  4.4.1. Absorption and Catalysis  4.4.2. Colloids and Emulsions
  5. Analytical Chemistry  5.1. Classical methods  5.1.1. Gravimetric Analysis  5.1.2. titrimeter  5.2. Instrumental methods  5.2.1. Chromatography  5.2.2. Spectroscopy  5.2.3. Electroanalytical methods  5.2.4. X-ray diffraction
  6. Industrial Chemistry  6.1. Petrochemistry  6.2. Chemical engineering principles  6.3. Green Chemistry  6.4. Pharmaceuticals and Drug Synthesis
  7. Biochemistry  7.1. Carbohydrates  7.2. Proteins and enzymes  7.3. Lipids and membranes  7.4. Nucleic acids  7.5. Metabolism and Bioenergetics  7.6. Enzyme kinetics and mechanism

Undergraduate → General chemistry → Stoichiometry ↓


Percent Yield and Purity


In the study of chemistry, especially at the undergraduate level, stoichiometry is an essential aspect that involves determining the amount of reactants and products in chemical reactions. Two important concepts within stoichiometry are percent yield and purity. These concepts help determine the efficiency of a reaction and the quality of the final product.

Theoretical yield

The theoretical yield is the maximum amount of product that can be produced from a given amount of reactants, assuming the reaction proceeds to complete conversion under ideal conditions.

For example, consider the reaction between hydrogen gas and oxygen gas to form water:

2H2 + O2 → 2H2O

If you start with 10 moles of H2 and 5 moles of O2, the stoichiometry of the reaction implies that you can theoretically generate 10 moles of H2O.

Actual yield

Actual yield is the measured amount of product obtained from a reaction. Due to various factors such as incomplete reactions, side reactions, and losses during product recovery, actual yield is often less than the theoretical yield.

Using the previous example, suppose you only separate 8 moles of water. Here, the actual yield is 8 moles, which is less than the theoretical 10 moles.

Percent yield

Percent yield is a measure of the efficiency of a reaction, expressed as a percentage. It is calculated using the formula:

Percent Yield = (Actual Yield / Theoretical Yield) * 100%

Using the example of water formation, the percentage yield would be:

Percent Yield = (8 moles / 10 moles) * 100% = 80%

Visual example

Theoretical Yield (10 mol) Actual yield (8 mol)

Purity

Purity refers to the amount of the desired product relative to the amount of the impure sample. This is particularly relevant in the case of products that are in crude form after a reaction and require further purification.

The purity of a substance is expressed as a percentage and is calculated as follows:

Purity (%) = (Mass of Pure Substance / Total Mass of Sample) * 100%

Continuing our examples, suppose you have a 12-gram sample that contains 9 grams of pure product. The purity would be:

Purity (%) = (9g / 12g) * 100% = 75%

Visual example

Total sample (12 g) Pure substance (9 g)

Real-world applications

Understanding percent yield and purity is important in various fields such as pharmaceuticals, materials science, and food processing.

Examples in pharmaceuticals

In drug manufacturing, a high percentage yield ensures maximum efficiency and cost-effectiveness. Also, high purity of the drug is important for patient safety and regulatory approval.

Examples in materials science

In the production of materials such as polymers, achieving near-theoretical yields can reduce waste and increase economic viability. The purity of a material affects its properties such as strength and flexibility.

Common challenges

Some common challenges in achieving high percentage yield and purity are as follows:

  • Incomplete reactions where not all reactants are converted into products.
  • Competing side reactions that create unwanted byproducts.
  • Loss of product during separation and purification process.

Improving percent yield and purity

Several strategies can be used to increase the yield percentage and product purity:

  • Optimizing reaction conditions such as temperature, pressure, and concentration.
  • Using catalysts to make reactions happen more efficiently.
  • Implement effective purification techniques such as recrystallization, distillation or chromatography.

Example: Improvement in yield by catalysis

Consider a reaction catalyzed by an enzyme or metal catalyst, which lowers the activation energy and increases the reaction rate, leading to a more complete conversion.

Conclusion

Percent yield and purity are fundamental concepts in stoichiometry that provide information about the efficiency and quality of chemical reactions. A good understanding of these topics is essential for anyone working in chemistry-related fields, as they affect both the economic and practical feasibility of industrial and laboratory processes.


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Percent Yield and Purity

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