A-Level Chemistry revision notes

A-Level (A2/AS) Chemistry revision notes providing information and assistance across all examination boards including AQA, CIE, OCR, Edexcel, Eduqas & WJEC. Chemistry is a complicated A-Level with a lot of content and information to work through. We have put together some of the best revision notes and learning materials to hopefully make sitting your Chemistry A-Levels a little bit easier and stress-free.

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Types of Chemical Bonds

A chemical bond is a type of attraction between atoms, molecules, or ions that is the basis for the formation of all chemical compounds.  There are 4 major types of chemical bonds which are represented below: Types of Chemical Bonds Ionic Bond  Compounds that are composed of ions are referred to as ionic compounds, and ...

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Ionic Equations

Ions are formed when atoms or molecules lose or gain electrons; therefore, ions have an overall positive or negative charge. If an atom or a molecule loses an electron → positively charged ion If an atom or a molecule gains an electron → negatively charged ion As we already know, solution results from a solute ...

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Empirical and Molecular Formula

Empirical Formula To determine the formulas for different compounds, scientists did not use the periodic table, rather formulas were determined through the quantitative analysis which determines the percent composition of a compound. After identification of the relative mass of each atom in a particular compound, one can determine the empirical formula of that compound. Therefore, ...

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The Ideal Gas Equation

The physical properties of gases are dependent upon 4 variables which are the following: Pressure – P Volume – V Temperature – T (Kelvin) Number of moles – n  Several laws describe the changes in the state of gas by defining variable or constant quantities: Boyle’s Law – variable pressure and volume; constant temperature and ...

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Solutions and Titrations

Volumetric Analysis Techniques in Solutions and Titrations Volumetric analysis is an essential technique used to accurately determine the concentration, molar mass, or formula of an unknown compound.  Type of Volumetric Analysis Techniques There are several general types of volumetric analysis techniques, depending on the nature of the reaction occurring during the titration: Acid-Base titrations – ...

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Reaction Masses and Atom Economy

Summary of Reaction Masses and Atom Economy When a reaction occurs, we usually assume that the yield of the reaction is 100%. But this is not true in reality since the actual percent yield (or experimental yield) of a reaction is lower than the theoretical value.  There are several ways to determine the percentage of ...

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The Mole

Definition: The mole (n) The mole (n), abbreviated as mol, is a fundamental chemical quantity that characterizes the amount of substance. It is defined that 1 mole of any substance contains 6.02x1023 particles (atoms, molecules, ions, electrons). 6.02x1023 is a unique number, called Avogadro’s number. Amedeo Avogadro was the first scientist to determine the actual ...

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Thermochemistry

Summary Thermochemistry is a branch of Thermodynamics, a scientific field that comprises the relationships between heat, work, and other forms of energy resulting from different chemical and physical processes. Thermochemistry itself is defined as energy changes when a chemical reaction takes place.  Energy is the capacity to supply heat or do work. Thermochemistry is concerned ...

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Bond Enthalpy

Summary Bond enthalpy, also referred to as bond energy or bond dissociation energy, is the energy required to break a particular covalent bond in one mole of molecule in a gaseous state. The term was previously used as “bond strength.” These terms have the same exact meaning; therefore, they can be used interchangeably.  Bond Enthalpy ...

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Essential Elements for Life

Summary There are about 118 sorted by atomic number in the Periodic Table. 94 out of these 118 elements are considered natural elements, and 20 to 25% of them are known as “essential to life.” These essential elements are quite similar among organisms but vary from species to species (e.g., humans need 25 elements while ...

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