1.8.2

Percentage Yield

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Percentage Yield

The percentage yield for any reaction is usually less than 100%. The following 5 factors cause deviations from 100%.

Incomplete reactions

Incomplete reactions

  • An incomplete reaction can happen because:
    • The reaction is very slow and hasn't been given enough time to happen.
  • The reaction is reversible and some of the products have turned back into reactants.
  • This reduces the percentage yield.
Waste

Waste

  • Some of the chemicals will remain stuck to the glassware and will be wasted.
  • This reduces the percentage yield.
Extraction

Extraction

  • It might be difficult to fully separate the product from the reaction mixture.
  • This reduces the percentage yield.
Side reactions

Side reactions

  • Unexpected reactions (side reactions) can happen. This may mean that the intended product is not created.
  • This reduces the percentage yield.
Hydration

Hydration

  • If a reaction is carried out in water, any extracted product may be 'wet'
  • This means that there is water in the extracted product.
    • Water is generally extremely difficult to fully remove from a product.
  • If a percentage yield is calculated to be over 100%, it is likely that your product is full of water.

Calculating Percentage Yield

The percentage yield of a reaction is calculated as the real yield divided by the theoretical yield multiplied by 100.

Real yield

Real yield

  • The real yield is the mass of the desired product obtained from a reaction.
Theoretical yield

Theoretical yield

  • The theoretical yield is the maximum mass of a product that could possibly be created from a reaction.
  • This can be calculated from a balanced equation if we know the mass of the reactants.
Percentage yield

Percentage yield

  • A comparison of the real and theoretical yields of a reaction.
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1

Structure - Models of the Particulate of Matter

1.1

Introduction to the Particulate Model of Matter

1.1.1States of Matter1.1.2Kinetic Molecular Theory1.1.3Simple Sphere1.1.4Changing State1.1.5Forces Between Particles1.1.6Changes of State1.1.7Predicting States1.1.8Changing State HyperLearning1.1.9Ionization Energy
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Electron Configuration

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Ideal Gases

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1.6

Elements, Compounds & Mixtures

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1.7

States of Matter & Changes of State

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Reacting Masses &. Volumes

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Solutions

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Structure - Models of Bonding & Structure

2.1

The Ionic Model

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2.2

The Covalent Model

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Covalent Structures

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The Metallic Model

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From Models to Materials

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Valence Electrons & Ionic Compounds

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Molecular Shape

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Intermolecular Forces

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3

Structure - Classification of Matter

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Halogens

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Functional Groups: Classification of Organic

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Functional Group Chemistry

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Alkanes

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Alcohols

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Halogenoalkanes

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Reactivity - What Drives Chemical Reaction?

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Endothermic & Exothermic Reactions

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4.2

Enthalpy of Reaction, Formation, & Hess' Law

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4.3

Entropy

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Reactivity - How Much, How Fast & How Far?

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Kinetics

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Rates of Reaction

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Stoichometry

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Le Châtelier’s Principle

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Introduction to Equilibrium

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Equilibrium Constant

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Reaction Quotient & Equilibrium Constant

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Reactivity - The Mechanisms of Chemical Change

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Proton Transfer Reactions

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The pH Scale

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6.3

Strong & Weak Acids and Bases

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Acid Deposition

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Types of Organic Reactions

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Oxidation & Reduction

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Electrochemical Cells

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Titration

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Acid-Base Titrations

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Measurement, Data Processing & Analysis

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Uncertainties & Errors in Measurements & Results

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Graphical Techniques

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Spectroscopic Identification of Organic Compounds

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Infrared Spectroscpy

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Practice questions on Percentage Yield

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  1. 1
    To understand percentage yield, it can be useful to imagine you are baking a cake...Flashcard
  2. 2
    Factors that reduce percentage yield:Fill in the list
  3. 3
    The percentage yield for any reaction is almost always less than:Multiple choice
  4. 4
    Which of the following is not a reason for percentage yield to be less than 100%?Multiple choice
  5. 5
    What features of a reaction make it more likely to be incomplete?Fill in the list
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Balancing Equations & Ionic Equations

Molarity