Energy + Entropy + Reactions Flashcards
Define stoichiometry
The relationship between amounts of reactants and products
What are the 2 principles of collision theory
- Reactant molecules must collide with sufficient energy for a reaction to occur.
- Reactants must also be in the correct orientation
What is exo and endothermic
- Exothermic is energy released when bonds are formed
- Endothermic is energy consumed when bonds are broken
What is the name and unit for the emasure of energy change
- ΔH
- enthalpy change
- kilojoules per mole (kJ/mol)
simple equation for enthalpy change
reactants - products = ΔH
What do the different outcomes of ΔH mean
- if ΔH is - then reaction is exothermic
- if ΔH is + then reaction is endothermic
What do exo and endo energy level graphs look like
- exothermic - reactants higher than products
- endothermic - reactants lower than products
What does Maxwell-Boltzmann distribution curve show
Shows how the energies of particles in a gas are distributed at a specific temperature in regard to activation energy
How to determine the rate of reaction
Determined by the number of molecules with sufficient energy for a reaction
Name the 4 ways to increase the rate of reaction
- Raise the temperature
- Increase concentration of reactants
- Increase surface area of reactants
- Use a catalyst
How does heat increase rate of reaction?
- Increasing the temperature (heat) gives more kinetic energy to the reactant molecules
- Increasing the chance of a collision between two reactant molecules with sufficient energy for reaction
How can concentration increase the rate of reaction?
Increases the number of molecules, therefore increasing the chance of a collision between two molecules with sufficient energy for a reaction
How does surface area increase the rate of reaction?
By exposing more of the molecules of the substance to a surrounding reactant more molecules are available to react with the surrounding reactant
What does a catalyst do and how does it do it?
- Increases the rate of a reaction, without being consumed by the reaction
- By lowering the activation energy
What is a feasible reaction?
A reaction is described as feasible (or spontaneous) if it is energetically favourable at a certain temperatur
What is entropy?
Entropy is a measure of disorder
Name 2 things that increases the entropy of a reaction
- Gases have more entropy than solids
- Lots of small particles have more entropy than one large molecule
What is Gibbs free energy and the equation
- Gibbs free energy (G) is the energy available in a substance to do work
- G = ΔH - (T x ΔS)
Define exergonic
- A reaction that has a negative ΔG (difference in G between products and reactants)
- This means it is thermodynamically feasible
How do unfeasible reactions happen in the body?
- Energy coupling
- Endergonic and exergonic reactions are coupled together
- Example: ATP synthesis and cellular respiration
Define energonic
- A reaction that has a positive ΔG
- Endergonic reactions are not thermodynamically feasible
What is the overall equation for a nuetralisation reaction
Acid + Base –> salt + H2O
What is a combustion reaction
Rapid reaction with oxygen
What is biological decomposition reactions + examples
- Hydrolysis of energy storage molecules
- Glycogen –> Glucose
- Triglycerides –> Glycerol + fatty acids
