Multiple Choice QuestionsThe pair of amphoteric hydroxides is
Al(OH)3, LiOH
Be(OH)2, Mg(OH)2
B(OH)3, Be(OH)2
Be(OH)2, Zn(OH)2
Which of the following is only acidic nature?
Be(OH)2
Mg(OH)2
B(OH)3
Al(OH)3
C.
B(OH)3
B(OH)3 in aqueous medium coordinates a molecule of water to form the hydrated species . In this species, B3+ ion, because of its small size, exercises a high polarizing power thereby pulling the sigma electron charge of the coordinated O atom towards itself. The coordinated oxygen, in turn, pulls the sigma electron charge of the OH bond of the attached H2O molecule towards itself. This facilitates the removal of H+ ion from the O- H bond, as shown below.
Thus the solution of B(OH)3 in water acts as a weak acid. That is why it reacts with NaOH solution to produce the sodium salt.
On dissolving moderate amount of sodium metal in liquid NH3 at low temperature, which one of the following does not occur?
Blue coloured solution is obtained.
Na+ ions are formed in the solution.
Liquid NH3 becomes good conductor of electricity
Liquid ammonia remains diamagnetic
Which of the following reaction produces hydrogen ?
Mg + H2O
H2S2O8 + H2O
BaO2 + HCl
Na2O2 + 2HCl
Assertion: Mg is not present in enamel of human teeth.
Reason : Mg is an essential element for biological functions of human.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false.
Match the flame colours of the alkaline earth metal salts in the Bunsen burner.
| A. Calcium | p. Brick red |
| B. Strontium | q. Apple green |
| C. Barium | r. Crimson |
A - p; B - r; C - q
A - r; B - p; C - q
A - q; B - r; C - p
A - p; B - q; C - r
Addition of sodium thiosulphate solution to a solution of silver nitrate gives X as white precipitate, insoluble in water but soluble in excess thiosulphate solution to give Y. On boiling in water, Y gives Z. X, Y and Z respectively are
Ag2S2O3, Na3[Ag(S2O3)2], Ag2S
Ag2SO4, Na[Ag(S2O3)2], Ag2S2
Ag2S2O3, Na5[Ag(S2O3)3], AgS
Ag2SO3, Na3[Ag(S2O3)2], Ag2O
The aqueous solution of which of the following salt will have the lowest pH ?
NaClO3
NaClO
NaClO4
NaClO2
Switch
