AQA A-Level Chemistry 7405
Atomic Structure
Amount of Substance
Bonding
Energetics and Thermodynamics
Kinetics
Chemical Equilibria
Redox and Electrochemistry
Acids and Bases
Periodicity and Group Chemistry
Period 3 Elements and Their Oxides
Transition Metals
Introduction to Organic Chemistry
Hydrocarbons
Halogenoalkanes, Alcohols and Organic Analysis
Carbonyls, Carboxylic Acids and Derivatives
Aromatic Chemistry and Amines
Polymers, Amino Acids, Proteins and DNA
Organic Synthesis, NMR and Chromatography
Energetics and Thermodynamics
Enthalpy Change and Standard Conditions
- 3 things to know
- Papers 1 and 3
Overview
Exothermic and endothermic changes, standard conditions, and the standard enthalpy definitions.
What you need to know
Answer each one before you reveal it.
Besides pressure, what else must be stated for standard conditions?
How is a standard enthalpy change at 298 K symbolised?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is enthalpy change (ΔH)?
Model answer
The heat taken in or given out when pressure is held constant
- 2
Under what conditions is enthalpy change measured?
Model answer
Constant pressure
- 3
What pressure is specified for standard conditions?
Model answer
100 kPa
- 4
Besides pressure, what else must be stated for standard conditions?
Model answer
A temperature (e.g. 298 K)
- 5
How is a standard enthalpy change at 298 K symbolised?
Model answer
ΔH°₂₉₈ (with the theta symbol and temperature subscript)
- 6
What does the term exothermic mean in relation to a reaction?
Model answer
A reaction that releases heat energy to the surroundings (negative ΔH)
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