Module 5 Flashcards
Conc. time graphs?
Zero - \
1st - curve down
2nd - large surge down
Rate conc. graph?
Zero = — 1st = / 2nd = curve up
Rate determining step
The slowest step within the sequence
Arrenhius equation?
K = A e-Ea/RT
Log
LnK = -Ea/RT + LnA
Y = mx + c
Gradient = -Ea/R
Y axis intercept = lnA
Mole fraction?
No of moles of A / no of moles in gas mixture
Partial pressure?
Mole fraction of A X total pressure
Weak acid calc?
Ka
HA <=> H+ + A-
Strong bad/ strong acid?
Kw
Kw = [H+][OH-]
1 x 10-14
Weak base = POH = -log(OH-)
pH = 14 - POH
Buffer
System that minimises pH changes when small amounts of an acid or base are added
Weak acid and conjugate base
Titration curves?
Neutralisation
Equivalence point - volume of one solution that exactly reacts with the volume of the other
End point - indicator contains equal concentrations of HA and A-, colour between the two
Lattice enthalpy?
The enthalpy change that accompanied the formation of one moles of an ionic compound from its gaseous ions
K+ + cl- —> kcl (s)
Exothermic always negative
Enthalpy change of formation
EC that takes place when one mole of a compound is formed from its elements
Na (g) + 1/2Cl2 (g) —> Nacl (s)
Enthalpy change of atomisation?
EC that takes place for the formation of one mole of a gaseous atom from the element
First ionisation energy
The enthalpy change required to remove one electron from each atom of one mole of gaseous atoms to form one mole of gaseous +1 ions
First electron affinity
Energy change that takes place when one electron is added to an atom in one mole of gaseous atoms to form one mole of gaseous -1 ions
Enthalpy change of solution
Enthalpy change that take solace when one mole of a solute dissolves in a solvent
Enthalpy change of hydration
Enthalpy change that accompanies the dissolving of gaseous ions in water to form aqueous ions
Factors affecting lattice enthalpy
Ionice size - increase, attraction between ions decreases, lattice enthalpy less negative, MP decrease
Ionic charge - increases, attraction increase, lattice enthalpy more negative
Factors affecting hydration enthalpy
Ionic size - increase, attraction between water molecules and ions decreases, hydration energy less negative
Ionic charge - increase, attraction with water molecules increase, more negative
Entropy?
🔼s
The greater the entropy the greater the dispersal of energy hence the greater the disorder
At 0K no energy entropy 0
Always Positive entropy
Standard entropy?
Entropy of one mole of a substance, standard conditions
Gibbs free energy
🔼G = 🔼H - t🔼S
🔼G < 0 to be feasible
Primary fuel cell
Non rechargeable
Electrical energy produced by oxidation and reduction of electrodes
Reactions cannot be reversed, chemicals used up and voltage will fall.
Generally alkaline based
Secondary fuel cell?
Rechargeable
Reversed during recharging, chemicals regenerated
Fuel cells?
Use energy from the reaction of a fuel with oxygen to create a voltage
Transition elements
Dblock elements that form at least one ion egg a partially filled d-orbital
Form compounds with different oxidation states
Form coloured compounds
Can act as catalysts
Complex ions
Formed when one or more negatively charged ions bond to central metal ions (Ligands)
Ligand - molecule or ion that donates pair of e- to central metal ion to form coordinate bond
Ligand substitution
Copper and ammonia
Cooper ions and ammonia
[Cu(H2O)6]2+ pale blue
add ammonia
First see pale blue ppt Cu(OH)2
Then ppt dissolves in excess ammonia create dark blue solution [Cu(NH2)4(H2O)2]2+
Ligand substitution
Copper and chloride
[Cu(H2O)6]2+ pale blue
Add 4Cl-
[CuCl4]2- yellow solution
Ligand substitution
Chromium ions
Chromium sulphate dissolved in water
[Cr(H2O)5SO4]+ green solution
Precipitation reaction?
Two aqueous solutions containing ions react together to form an insoluble ionic solid precipitate.
Qualitative analysis
Cu2+ blue —> blue ppt Fe2+ pale green —> green ppt Fe3+ pale yellow —> orange/brown ppt Mn2+ pale pink —> pink/brown ppt Cr3+ violet —> grey/green ppt
Addition of OH-
