Reaction Feasibility

Cards (10)

Thermochemistry
The study of energy (enthalpy) changes that take place during chemical reactions
Enthalpy of formation
Standard enthalpy of formation is the enthalpy change when one mole of a substance is formed from its elements in their standard states
What is standard state?
The most stable state of a substance at standard conditions (usually a pressure of 1 atmosphere and a specified temperature - usually 298K or 25 degrees)
What is the enthalpy of formation of an element?
Zero - no enthalpy change involved
Standard Enthalpy
Standard enthalpy = (enthalpy of formation of products) - (enthalpy of formation of reactants)
What is a sponteous reaction?
A reaction where it happens of its own accord (doesn’t need energy input). This means it will tend towards the products rather than reactants This has no relation to rate (can be fast/slow)
What type of reactions are exothermic reactions?
Almost all of them are spontaneous at standard conditions as the products have lower enthalpy than the reactants and are therefore more energetically stable.
How can the spontaneity/feasibility of chemical reactions be determined?
By the enthalpy change alone
What is entropy?
A measure if the degree of disorder in a system - the greater the entropy, the greater the disorder
What do entropy values depend on?
State of chemicals
Solid - least disordered
Liquid
Gas - most disordered