Boron

Question 1

Borax
Color
Formula
Actual formula
In water

Answer 1

White crystalline
Na2B4O7. 10H2O
Na2[B4O5(OH)4].8H2O
Borax dissolves in water to give alkaline sol - and also gives H3BO3

Question 2

Borax bead

Answer 2

Metaborate
CoO - blue - Co(BO2) 2

Question 3

Orthoboric acid

Colour and feel
Normal water
Hot water
Prep
Str
Type of acid
On Heating at 370K

Answer 3

White crystalline, soapy touch
Normal water - sparingly soluble
Hot water - highly soluble
Borax + acid and Hydrolysis of most boron compounds
Layer structure with H Bonding
Weak mono basic acid (Lewis not protonic)
H3BO3 –∆–> HBO2 –∆–> B2O3

Question 4

Simplest boron hydride

Answer 4

Diborane

Question 5

Prep of diborane

Answer 5

Bf3 and lialh4 gives b2h6, lif3 and 3 alf3
Nabh4 and i2 gives b2h6, nai and h2 (Lab)
Bf3 and Nah gives b2h6 and naf(industrial scale)

Question 6

Diborane

Colour
Toxic or not
Exposure to air
Burns in oxygen
On hydrolysis
With Lewis base
With ammonia

Answer 6

Colourless.
Highly toxic
Catches fire
Burns in oxygen to release enormous amt of energy
Boric acid
Undergoes cleavage reactions to give borane adducts
Gives borazine

Question 7

Uses of boron

Features of boron
Boron fibres
Nuclear industry
Borax and boric acid
Borax
Boric acid

Answer 7

Hard, refractory solid, high melting point, low density, low electrical conductivity.
Bullet proof vest, light composite material for aircraft.
Due to high ability to absorb neutrons - used as protective shield and control rods
Heat resistant glasses (pyrex), glasswool and fibre glass
Soldering metal, medicinal soaps
Antiseptic

Question 8

Uses of aluminium

Features of Al
Weight to weight basis difference between aluminum and copper
Why did they stop using Al in household.

Answer 8

High tensile strength, high electrical and thermal conductivity.
Twice of copper.
Reduced because of its toxic nature