Physical Chemistry Flashcards
Exothermic reactions
They release heat energy meaning that the temperature increases.
In exothermic reactions, the temperature of the surroundings increases and the heat content of the system falls.
Endothermic reactions
It takes in heat energy meaning that the temperature decreases.
In endothermic reactions, the temperature of the surroundings decreases and the heat content of the system increases
Neutralisation reactions
These always give energy out
Displacement reactions
These can either take energy in or give it out
Combustion reactions
These always give energy out
Calorimetry experiments
- Enthalpy changes of reactions in solution
- Enthalpy changes of combustion
Heat change equation
Q = M x C x ΔT
Q being the heat energy change
M being the mass of the substance being heated
C being the specific heat capacity
ΔT being the change in temperature
Calculating molar enthalpy change
Energy released per gram of fuel:
Energy released per gram = energy released / mass of fuel burned
Energy released per mole of fuel:
Energy released per mole = energy released / number of moles
ΔH = Q/N
units are KJ/mol
Energy level diagrams
X
Bond energies
Bond breaking is an endothermic process as energy is taken in (positive number is endothermic)
Bond making is an exothermic process as energy is released when new bonds are formed (negative number is exothermic)
Bond energy calculations
Enthalpy change (ΔH) = Energy taken in - Energy given out
Practical: Investigating Temperature Changes
Reaction between HCl and NaOH
Rates of reaction
- Temperature
- Concentration
- Surface area
Catalyst on rate of reaction
Speeds up the rate of reaction providing an alternative pathway without being used up
Activation energy
X
