Home > Subjects > Chemistry > Level 2 > 2.6 Thermochemistry and equilibrium > Subject content
- Subject: Chemistry
- AS: AS90310
- Level: 2
- Credits: 5
- External
Chemistry 2.6 Describe thermochemical and equilibrium principles
Subject content
Make sure you have up-to-date course notes.
Thermochemical principles that you may be tested on include:
- classification of reactions as exothermic and endothermic
- determination of enthalpy changes
- factors affecting rates of reaction. Restricted to changes in:
- concentration
- temperature
- surface area
- the presence of a catalyst.
Check out Dr Brown’s chemistry clinic on Energy transfers in chemical reactions, which revises your year 11 and some of your year 12 work on this topic.
Enthalpy change relates to the change of energy in a chemical reaction.
Thermodynamics is another name given to the chemistry concerned with changes in heat, which is one form of energy. Check out some basic nomenclature and definitions.
- Classification of reactions as exothermic or endothermic given:
- energy diagrams
- the sign of DrH, or
- heat changes.
- Calculation of enthalpy changes from:
- given amounts or mass of substances
- a balanced equation, and
- DrH.
For an example of a calculation of enthalpy change, check out thermochemical stoichiometry. Note that delta H is the same as saying D H and refers to the change in enthalpy or energy of a reaction.
Equilibrium principles that you may be tested on include:
- Describing the dynamic nature of equilibrium.
- Explanation of the direction in which reaction occurs on changing a system at equilibrium. Restricted to changes in:
- temperature ( DrH given)
- concentration
- pressure, or
- addition of a catalyst.
- Writing equilibrium constant expressions for homogeneous systems from given equations and the significance of the magnitude of K.
- Description of acids and bases in terms of proton transfer.
- Calculations involving Kw and pH.
- Properties of aqueous solutions of strong and weak acids and bases including ionic species such as NH4+. The properties are restricted to:
- conductivity
- rate of reaction
- pH.
- Recognition of acid-base properties of ionic compounds that contain only one ion that changes the pH of water.
Revise your work on the GCSE Creative Chemistry PowerPoint presentations
