Chem 2a

Question 1

TOLLENS’ or SILVER MIRROR test

Answer 1

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+

Question 2

FEHLING’S test

Answer 2

Blue solution of Cu2+ in an alkaline solution.
On heating w/ aldehyde, red-brown ppt. of Cu2O forms.
CH3CHO + Cu2+ + 2OH– –> CH3COOH + Cu2O + 2H2

Question 3

Uses of esters

Answer 3

SOLVENT
PLASTICISERS
FOOD FLAVOURING

Question 4

Ester as a solvent

Answer 4

Used in glues/lacquers. Have low boiling points and evaporate quickly.

Question 5

Ester as a plasticiser

Answer 5

Make plastics softer and more flexible e.g. cling-film.

Question 6

Ester as food flavouring

Answer 6

Have sweet and fruity odours often used in food.

Question 7

Saponification

Answer 7

Hydrolysis of ester, triglyceride to form acid and glycerol.

Question 8

Glycerol as a solvent

Answer 8

Mixes easily with water and prevents materials drying out too quickly – used in foods and cosmetics.

Question 9

Properties of transition metals

Answer 9

• FORM COMPLEX IONS
• FORM COLOURED IONS
• HAVE VARIABLE OXIDATION STATES
• SHOW CATALYTIC ACTIVITY

Question 10

Complex ion

Answer 10

A COMPLEX contains a central metal atom/ion surrounded by co-ordinately bonded LIGANDS

Question 11

Ligand

Answer 11

Molecules/ions w. an available lone pair

Question 12

What causes colour in transition metal ions?

Answer 12

INCOMPLETE d-SUBSHELLS.

Question 13

What causes a colour change in transition metal ions?

Answer 13

Change in:
- oxidation state of the metal
· coordination number of the complex
· type of ligand involved

Question 14

Chromate (VI)

Answer 14

CrO4^(2–)
Yellow
Stable in alkali only

Question 15

Dichromate (VI)

Answer 15

Cr2O7^(2–)
Orange
Stable in acid only

Question 16

Manganate (VII)

Answer 16

MnO4–
purple pale pink
good oxidising agent

Question 17

ADVANTAGE OF KMnO4

Answer 17

Does not need an indicator.

Question 18

ADVANTAGES OF K2Cr2O7

Answer 18

Can be used in the presence of chloride.

It is stable and can be a PRIMARY STANDARD.

Question 19

Haber process

Answer 19

N2(g) + 3H2(g) –> 2NH3(g)
· 450°C
· 50 MPa
· with a catalyst of iron, Fe

Question 20

Contact process

Answer 20

2SO2(g) + O2(g) –> 2SO3(g)
· 450°C
· 100-200 kPa
· with a catalyst of vanadium(V) oxide, V2O5

Question 21

Hydration of ethene w/ steam

Answer 21

CH2=CH2(g) + H2O(g) –> CH3CH2OH(g)
· 300°C
· 7 MPa
· with a catalyst of phosphoric acid, H3PO4

Question 22

Charge on level of acidity

Answer 22

Greater the charge the greater the acidity

Question 23

Size of atom on level of acidity

Answer 23

Smaller the radius the greater the acidity

Question 24

Lewis Acid

Answer 24

An electron-pair acceptor

Question 25

Lewis Base

Answer 25

An electron-pair donor

Question 26

Factors of acidity level

Answer 26

• Charge - the greater the charge the greater the acidity
• Size - the smaller the radius the greater the acidity
  Make up charge density.

Question 27

Brønsted-Lowry acid

Answer 27

Proton donor

Question 28

Brønsted-Lowry base

Answer 28

Proton acceptor