REAL CHEM PRACTICAL (wednesday and friday)

2 metals which are dipped into a salt solution of their own ions. they are connected by a wire anda salt bridge, electrons flow from the metal with a more negative electrode potential to the other more positive electrode potential, generating electricity

connects the 2 solutions in an electrochemical cell, allowing the ions to move through it, completing the circuit and balancing out the charges

roll filter paper and dip into KNO3

single line for change of state double line for salt bridge e.g. Zn(s) / Zn(aq) // Cu2+(aq) / Cu(s)

Pt electrode at 298K in 1moldm-3 dilute sulphuric acid, with H2 gas at 1atm

given potential 0 vaults so all other metals EMF is compared against this

more positive (rhs) - more negative (lhs)

Pt(s) / 2Cl-(aq), Cl2 (g) //

if it has a positive EMF

they can form different oxidation states as the energies of the 4s and 3d orbitals are very similar, so the energy required to remove any of these electrons is similar

ΔG = ΔH - TΔS

electrochemical is better as it allows for liquids, Gibbs must be in their standard states

+3, +6

+2, +4, +7

+2, +3

+2

+1, +2

[CoCl4]2- blue [CuCl4]2- yellow/green

[Fe(H2O)6]2+ pale green [Fe(H2O)6]3+ yellow [Cr(H2O)6]3+ dark green [Co(H2O)6]2+ pink [Cu(H2O)6]2+ blue [Cu(NH3)4(H2O)2]2+ royal blue

more negative EMF

more positive EMF

Cl2 + 2e- --> 2Cl- Fe2+ --> Fe3+ + e- so, Cl2 + 2Fe2+ --> 2Cl- + 2Fe3+

Fe2+ --> Fe3+ + e- Cr2O72- + 14 H+ + 6e- --> 2Cr3+ + 7H2O so, 6Fe2+ + Cr2O72- + 14H+ --> 6Fe3+ + 2Cr3+ + 7H2O

H2O2 --> O2 + 2e- + 2H+ MnO4- + 5e- + 8H+ --> Mn2+ + 4H2O so, 5H2O2 + 2MnO4- + 6H+ --> 5O2 + 2Mn2+ + 8H2O

2S2O32- --> S4O62- + 2e- I2 + 2e- --> 2I- so, 2S2O32- + I2 --> S4O62- + 2I-

starch

2Cu2+ + 4I- --> 2CUI + I2

the larger the %error

bromine water orange to colourless

• metallic Na, produces H2 gas (squeaky pop test) or

• acidified dichromate (VI) orange to green or

• acidified permanganate (VII) purple to colourless or if 2-ol + I2/NaOH yellow ppt

warm with a mix of NaOH, ethanol, and water, then add nitric acid, then AgNo3 Cl white ppt Br cream ppt I yellow ppt

• 2,4-DNPH yellow-orange ppt or

• Tollen's reagent silver mirror or

• Fehling's reagent blue to brown

• 2,4-DNPH yellow-orange ppt or

• I2/NaOH yellow ppt

• carbonate, effervescence of CO2 to confirm add NaHCO3 turns blue litmus paper red, and produces fizzing

reduce to a primary amine, using LiAlH4 then add HNO2 below 10 degrees produces bubbles

• HNO2 below 10 degrees produces bubbles

heat with NaOH, ammonia gas produced test vapour using damp red litmus paper, turns blue

heat with NaOH sodium carboxylate salt produced add dilute sulfuric acid to produce a carboxylic acid, then test with blue litmus paper, turns red

add water, produces white misty fumes

blue litmus turns red

red litmus turns blue

• Br2 if white ppt for aromatic

• FeCl3 purple sol

• Br2 white ppt

• barium chloride ppt if positive

• nitric acid fizzes

Cr3+ grey-green ppt

Fe2+ dark green ppt

Fe3+ red-brown ppt

Cu2+ pale blue ppt

Cr3+ green solution

more negative to more positive

grey-green ppt

dark-green ppt

red-brown ppt

pale blue ppt

green solution

blue

yellow-green

pale green

yellow

dark green

pink

blue

royal blue