Energetics Flashcards
Enthalpy change
Energy change for a reaction at constant pressure
Standard Conditions
100 kPa at 298K
Enthalpy of formation
the energy change for the formation of one mole of a substance from it’s elements in their standard states
Enthalpy of combustion
the energy change when one mole of a substance is completely combusted in oxygen from standard states
Enthalpy of solution
the energy change when 1 mole of substance is dissolved in a solution
process is known as dissolution
How to calculate enthalpy changes in solutions
Use an insulator
Calculate the temperature change in K
of a known mass of water (often the total volume of the solutions involved)
How to calculate enthalpy changes for fuels
Use a calorimeter
Calculate the temperature in K
of a known mass of water
Calculating molar enthalpy changes
Calculate the energy change
divide by moles used
Saturation
When no more solute
can be dissolved in a solvent
excess can be filtered off
State the names and units for the following
Q= MC T
Q= Energy Change
M= Mass of water
C= specific heat capacity of water
T= temperature change in K
Calculating energy change per gram
Calculate energy change
divide by gramms used
Calculating energy change per gram
Calculate energy change
divide by grams used
Exothermic
Reactions that release energy to the surroundings
-ve
Endothermic
Reactions that take in energy from the surroundings
+ve
Activation Energy
Minimum energy needed
for a reaction to occur (break bonds)
