Chem 2a Flashcards
TOLLENS’ or SILVER MIRROR test
Colourless solution of Ag+ in NH3 containing [Ag(NH3)2]+.
If warmed with an aldehyde a silver mirror may deposit on the walls of the test tube.
CH3CHO + [Ag(NH3)2]+ + H2O –> CH3COOH + Ag + 2NH4+
FEHLING’S test
Blue solution of Cu2+ in an alkaline solution.
On heating w/ aldehyde, red-brown ppt. of Cu2O forms.
CH3CHO + Cu2+ + 2OH– –> CH3COOH + Cu2O + 2H2
Uses of esters
SOLVENT
PLASTICISERS
FOOD FLAVOURING
Ester as a solvent
Used in glues/lacquers. Have low boiling points and evaporate quickly.
Ester as a plasticiser
Make plastics softer and more flexible e.g. cling-film.
Ester as food flavouring
Have sweet and fruity odours often used in food.
Saponification
Hydrolysis of ester, triglyceride to form acid and glycerol.
Glycerol as a solvent
Mixes easily with water and prevents materials drying out too quickly – used in foods and cosmetics.
Properties of transition metals
- FORM COMPLEX IONS
- FORM COLOURED IONS
- HAVE VARIABLE OXIDATION STATES
- SHOW CATALYTIC ACTIVITY
Complex ion
A COMPLEX contains a central metal atom/ion surrounded by co-ordinately bonded LIGANDS
Ligand
Molecules/ions w. an available lone pair
What causes colour in transition metal ions?
INCOMPLETE d-SUBSHELLS.
What causes a colour change in transition metal ions?
Change in:
- oxidation state of the metal
· coordination number of the complex
· type of ligand involved
Chromate (VI)
CrO4^(2–)
Yellow
Stable in alkali only
Dichromate (VI)
Cr2O7^(2–)
Orange
Stable in acid only
Manganate (VII)
MnO4–
purple pale pink
good oxidising agent
ADVANTAGE OF KMnO4
Does not need an indicator.
ADVANTAGES OF K2Cr2O7
Can be used in the presence of chloride.
It is stable and can be a PRIMARY STANDARD.
Haber process
N2(g) + 3H2(g) –> 2NH3(g)
· 450°C
· 50 MPa
· with a catalyst of iron, Fe
Contact process
2SO2(g) + O2(g) –> 2SO3(g)
· 450°C
· 100-200 kPa
· with a catalyst of vanadium(V) oxide, V2O5
Hydration of ethene w/ steam
CH2=CH2(g) + H2O(g) –> CH3CH2OH(g)
· 300°C
· 7 MPa
· with a catalyst of phosphoric acid, H3PO4
Charge on level of acidity
Greater the charge the greater the acidity
Size of atom on level of acidity
Smaller the radius the greater the acidity
Lewis Acid
An electron-pair acceptor
Lewis Base
An electron-pair donor
Factors of acidity level
- Charge - the greater the charge the greater the acidity
- Size - the smaller the radius the greater the acidity
Make up charge density.
Brønsted-Lowry acid
Proton donor
Brønsted-Lowry base
Proton acceptor
