2.1 Enthalpy Flashcards
Work=?
Force × distance
Define 1 Joule
The amount of energy required to raise a 1kg substance, 10cm against the force of gravity
Define 1 calorie
The amount of heat necessary to raise the temperature of exactly 1g of water by 1°C
One food calorie =
1000cal OR 1kcal
5 types of Energy (KC PEN)
Kinetic
Chemical
Potential
Electromagnetic
Nuclear
Potential Energy (E) =
mgh
Kinetic Energy (E) =
½mv²
What is the first law of thermodynamics?
The energy of the universe is constant
Equation for change in Internal Energy (E)
ΔE = q + w
q = heat
w = work
What does Enthalpy Change (ΔH°) show?
It shows whether heat is released or absorbed during a chemical process
Enthalpy Change (ΔH°) formula
Products Enthalpy- Reactants Enthalpy
Heat/work put into a system, in a calculation, is a ……….. value
Positive
Heat/work put into system is endothermic
Is “work on the surroundings” positive change or negative?
Negative
What are the standard conditions of an element in its standard state?
Pressure = 1atm
Temperature = 25°C or 298K
Concentration for solutions = 1M
In exothermic reactions, the products are……..?
More stable
In endothermic reactions, the products are…..?
Less stable
Respiration
Endo or Exo?
Exothermic
Electron exited up a n group
Endo or Exo
Endothermic (energy put in)
Standard enthalpy of formation is….
The change in enthalpy when one mole of a compound is formed from its elements in their standard states
Pure element enthalpy of formation?
Defined as zero in its standard state
What is used to measure energy changes?
Colorimeter (works well with exothermic reactions)
Enthalpy Change equation?
ΔH = MCΔT
What is Hess’ law?
Overall enthalpy change in a reaction is independent to the route taken from reactants to products
Breaking bonds is?
Endothermic (energy put it)
Enthalpy Change formula
Bonds broken - bonds formed
Making bonds is?
Exothermic (negative value)
What equation is used to find enthalpy of a reaction when given all enthalpies of formation?
ΔH(reaction) = ΣHf (products) - ΣHf (reactants)
Remember ion formation Equations/definitions for born harber cycles
First ionisation energy
Enthalpy of atomisation
Lattice enthalpy
Etc
Semester 1 knowledge required on Tom Robshaw workshop
Delivered 25/04
Heat/work taken out of a system, in a calculation, has a ……….. value
Negative
Heat/work taken out of a system is exothermic
