A kettle which becomes furred-up in use has inside it a deposit composed mainly of :

Magnesium bicarbonate
Magnesium sulphate
Sodium sulphate
Calcium carbonate

Solution

The bicarbonates of Ca and Mg are decomposed to Ca and Mg carbonates by boiling.

Carbon and silicon belong to group 14. The maximum coordination number of carbon in commonly occurring compounds is 4, whereas that of silicon is 6. This is due to

large size of silicon
more electro positive nature of silicon
availability of d-orbitals in silicon
Both (a) and (b)

Solution

Due to non-availability of vacant d-orbitals, it can not exceed its coordination number more than four. Thus carbon never forms complexes e.g., [CCl₆]^2– deos not exist but [SiCl₂]^2– exists.

Lead is not affected by dil. HCl in cold because

Pb is less electronegative than H
PbO film is formed which resists chemical attack by acid
A protective coating of PbCl₂ is formed on Pb surface
PbO₂ film is always present on Pb surface, which resist chemical attack

Solution

Pb with dil HCl forms protective coating of PbCl₂.

Tin cry refers to

Conversion of white to grey tin
Tin plating
Conversion of white tetrahedral tin to white rhombohedral tin
Emission of sound while bending a tin rod

Solution

Tin cry is the emission of sound on bending the tin.

Tin plague is the

Conversion of stannous to stannic
Conversion of white tin to grey tin
Emission of sound while bending a tin rod
Atmospheric oxidation of tin

Solution

It is the conversion of white tin to grey tin at low temperature which crumbles into powder.

Aluminium has a great affinity for oxygen and its oxidation is an exothermic process. This fact is used in

preparing thin foils of aluminium
making utensils
preparing duralumin alloy
thermite welding

CO₂ and N₂ are non-supporters of combustion.However for putting out fires CO₂ is preferred over N₂ because CO₂

Does not burn
Forms noncombustible products with burning substances
Is denser than nitrogen
Is a more reactive gas

Solution

CO₂ being more dense covers the igniting material more effectively than N₂.

Newly shaped glass articles when cooled suddenly become brittle,therefore these are cooled slowly, this process in known as

Tempering
Annealing
Quenching
Galvanising

Solution

Annealing makes the glass soft.

Which one of the following is correct statement ?

The hydroxide of aluminium is more acidic than that of boron
The hydroxide of boron is basic, while that of aluminium is amphoteric
The hydroxide of boron is acidic, while that of aluminium is amphoteric
The hydroxide of boron and aluminium are amphoteric

Solution

B(OH)₃ ⇒ H₃BO₃ Boric acid
Al(OH)₃ ⇒ Amphoteric

Aluminium vessels should not be washed with materials containing washing soda since

washing soda is expensive
washing soda is easily decomposed
washing soda reacts with aluminium to form soluble aluminate.
washing soda reacts with aluminium to form insoluble aluminium oxide

Solution

UnAttempted

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Attempted

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Correct

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Wrong

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Complete