Chemistry OCR A

random bits i get wrong

how to purify aromatic compounds SOLIDS

Dissolve in minimum volume of hot solvent

Allow to cool

Filter under reduced pressure (buchner funnel)

wash with cold solvent and dry

scratch with glass rod - speeds up crystallisation

how to purify organic LIQUIDS

use separating funnel to separate organic layer from aqueous layer

wash with NaHCO3 to remove acidic impurities

add drying agent ( CaCl2 )

redistill at specific boiling point

what does heterolytic fission mean

the breaking of a covalent bond where both electrons from shared pair moves to ONE atom

what does homolytic fission mean

when a covalent bond breaks, each bonding atom receives one electron from the bonding pair, forming 2 radicals.

what are the naturally occurring elements you need to know

S8, P4

fill in blanks for colour of compounds

what do u add to hexaaqua structures to have ligand substitution

excess NaOH, Excess NH3, Cl- ions

happens with Cu, Cr

what compounds are used for Proton NMR

D2O- proton exchange ( for -OH -NH -SH)

CDCL3 - solvent

what compounds are used in CNMR

Si(CH3)4 - used as standard reference for calibration

CDCl3 - used as solvent (no protons to interfere w sample)

definition on a functional group

specific atom that is responsible for reactivity

why does stereoisomerism happen

different group on each carbon in double bond

double bond doesnt rotate

evidence for delocalised modol of benzene

all C-C bonds same length

enthalpy of hydrogenation of benzene is less exothermic than expected

describe diagram of filtration under reduced pressure

what are the reasons for a lower enthalpy change than expected in an experiment

incomplete combustion

heat loss to surroundings

evaporation of water

what are the colours of the halides in solution and organic

Cl2 + 2Br- → Br2 + 2Cl- (orange in cyclohexane)

Br2 + 2I- → I2 + 2Br- (purple in cyclohexane)

what transition metal forms square planar ions

Platinum

how to explain buffer formation

excess weak acid with Salt/strong base. partially neutralises. contains [acid] and [conjugate base] / [salt or H+]