Further physical Flashcards
Enthalpy
A value that represents heat content of system
Enthalpy change of atomization
enthalpy change when 1 mol of gaseous atom is formed from an element in standard state
Enthalpy change of hydration
enthalpy change when 1 mol of gaseous ions are dissolved in water
Enthalpy change of solution
enthalpy change when 1 mol of solute is dissolved in water
1st electron affinity
energy released when 1 mol of electron is added to 1 mol of gaseous atom, forming 1 mol of gasous 1- ions
Lattice enthalpy
Formation of 1 mol of ionic lattice from 1 mol of gasous ions
What is lattice enthalpy a measure of?
strength of ionic bonds in lattice
Describle born-haber cycle diagram
atomization + Ionisation + electron affinity + ΔH(LE)
= enthalpy change of formation
How to increase lattice enthalpy ?
1.↑ ionic charge ( ↑ p : e ratio )
2.↓ ionic radius ( ↓ dist. = ↑ attraction )
0th order conc-time graph
1st order conc-time graph
2nd order conc-time graph
0th order rate-conc graph
1st order rate-conc graph
2nd order rate-conc graph
properties of 1st order conc-time graph
exponential decay
[constant half-life]
how to find rate constant for 1st order reaction
k = ln(2) / t1/2
2 methods of investigating rate
- initial rate
- continuous monitoring of conc.
Describle measuring intial rate with
E.g. iodine clock
record time for color change
(e.g. colorless to blue-black)
initial rate = 1/time for color change
Assumption made to record initial rate
no significant change in rate in the period recorded
Describle how calorimetry is used to determine rate
- certain wavelength of light is emitted to solution
- absorbance is recorded
- conc is monitored as proportional to absorbance
Desrible lattice enthalpy cycle
Describle enthalpy change of hydration cycle
ΔH(LE) + ΔH(solution) = ΔH(hydration)
Factors that affects ΔH(hydration)
- ↑ionic charge
- ↓ionic radius
↑ionic density = ↑ attraction on H2O= ↓ΔH
Affect of Δtemp on rate constant
As Temp↑, k↑ , rate↑
Homogenous eqm
eqm species all in same state
Hetrogenous eqm
eqm species have different
states/ phase
How to determine Kc/Kp experiementally?
- Mix known moles of reactant and acid
- wait
- then titrate one of the products to find the conc at eqm
- then find all conc at eqm by stoichiometry
Factors that affect(/not) Kc/Kp
**Temp. **
Does not:
1. pressure
2. conc.
(causes eqm to shift to restore value)
effect of temp on Kc
if LHS -> RHS is endo
- eqm shifts to the right
- to restore temp
- ↑[products]
∴ ↑Kc
Define Bronsted-Lowry acid
A species that donates a proton
Define bronsted-Lowry bases
a species that accept proton
Define monobasic acid
A species that contains
1 ionisable hydrogen atoms
per molecule
Assumptions made when doing weak acid calculations
- [HA]i = [HA]eqm
- [H+]=[A-]
Ka equation for strong acid
pKa to Ka conversions
pka = -log Ka
How to find pH of strong bases
- Find the conc of [OH-]
- use Kw = [H+][OH-]
- find [H+]
2 methods of preparing buffer
- weak acid + its salt (conjugate base)
- weak acid + strong base
Define buffer solution
minimises change in pH when small amount of acid/base is added
Buffer senario
How does buffer minimises change in pH when acid is added
(3)
- [H+] ↑
- eqm shifts to the left
- ↓ [H+]
How does buffer minimises change in pH when base is added
(5)
- [OH-] increases
- H+ + OH- -> H20
- [H+] ↓
- eqm shifts to the LHS
- restores [H+]
How to set up neutralisation reaction
(5)
- Add measured volume of acid/base into conical flask
- place electrode (of pH meter) into solution
- Add base/acid to burrette
- add 1 cm3 at a time
- go to dropwise when pH changes rapidly
What are pH indicators?
How do they change color
Weak acid
conjugate acid-base have different color
what is the difference between
end point and equivilance point
End point - physical observation
equivilance point - theroritical, n(titrate) =n(analyte)
How to choose an indicator?
indicator range aligns with vertical section
pKa in the pH range of color change
why does pKa tell the range of the indicator
1.[A-] = [HA]
2.Ka = [H+]
3. pH = -log[H+]
position of the end point
Define Isoelectric point
pH at which a particular molecule carries no net electrical charge
redox chem
MnO4 2-
reduced to …
Mn 2+
[+7] -> [+2]
redox chem
Fe 2+
oxidised to …
Fe 3+
[+2] -> [+3]
redox titration
which acid is used to dissolve
iron sulphate
sulphuric acid
redox titration
Why other acids are not suitable to dissolve
in manganate + iron sulphate
Maybe oxidised or act as oxidising agent for other substance
Redox chem
iodine and thiosulphate
redox eq.
What is in the conical flask for following redox
+
purpose
iodine + thiosulphate
excess KI
oxidising agent
to generate Iodine
steps to determine end point
iodine + thiosulphate
- turning from yellow-brown to yellow
- add starch
- blue-black
End point at colourless
End point for iron + manganate
purple to
1st permanent pale pink colour
What is calorimetry measure
Wavelength of light - depending on color
Define transition metal
d-block element that forms at least 1 ion with incomplete d-subshell
2 d-block element that is not transition metal
Sc - only form Sc 3+
Zn - only form Zn 2+
two transition element that don’t have 4s ^2
copper and chromium [4s^1]
Bond angle of square planar
90 deg
how many water ligand is formed in aqueos metal complex ?
6
Colour of Cr 3+ (aq)
violet
Colour of Fe 2+ (aq)
green
Colour of Fe 3+ ion (aq)
yellow
Colour of Mn 2+ (aq)
pale pink
colour of Cu 2+ ion (aq)
Blue
Two transition aqueous ion with same colour with the OH substituted ligand
Fe 2+ and Cu 2+
Colour of Cr (OH)3 p.p.
grey-green
colour of Fe (OH)2 p.p.
green
colour of Fe (OH)3 p.p.
brown
colour of Mn (OH)2 p.p.
pale brown
colour of Cu(OH)2 p.p.
Blue p.p.
transition metal that has a colour change in
ex. OH-
Cr 3+ -> dark green
2 transition metals that changes colour in
**ex. NH3 **
Cr 3+ - purple
Cu 2+ - dark blue
3 types of transition metal reaction
- ligand substitution
- p.p. reaction
- redox
3 ligand substitution reaction
- Cr (aq) complex + NH3 ex.
- Cu (aq) complex + NH3 ex.
- Cu (aq) complex + 4 Cl- ligands
what is the formula + coordination no
of the complex formed from
Cu(H2O)6 + 4Cl-
[CuCl4]2-
colour of [CuCl4]2-
yellow
What is Haem and its function
- iron complex
- forms ligand bonds with O2
- also bond with CO ligand - but stronger
what is the oxidising agent of Fe 3+ (to Fe 2+)
MnO4- ( goes to Mn 2+ )
reducing agent of Fe 3+ (to Fe 2+)
I- (iodide ion)
colour of Fe 3+
orange-brown
colour of Fe 2+
pale-green
colour change of iron-manganate titration
purple to colourless
colour of Cr^3+ in redox
green
colour of Cr2O7^2-
orange
colour of Cr 2+
Blue
Colour of Copper iodide p.p. (CuI)
white
