P-block XII (grp 15,16..)

Question 1

N2 is ______ while others are

Answer 1

N2 is diatomic others are polyatomic.

Question 2

All except ____ show allotropy. (In grp 15)

Answer 2

N

Question 3

N cant form d π - p π bond ??

Answer 3

Bcz of absence of d-orbital

But can show p π - p π bond

Question 4

Common oxidation state of grp 15 is

Answer 4

+3,-3,+5

Question 5

Tendency to show -3 oxidation state ______ down the grp due to??

Answer 5

Decreases.

Due to increase in size and metallic character.

Question 6

____ hardly forms any cmpd in -3 oxi. State?

Answer 6

Bi

Question 7

Stability of ____ oxi. State increases while of ____ decreases down the group.(grp 15)

Answer 7

+3 increases , +5 decreases

Due to inert pair effect.

Question 8

Characteristic compound of Bi in +5 oxi. State is??

Answer 8

BiF5

Question 9

3HNO2 —->

Answer 9

HNO3 +H2O +2NO

Question 10

All elements of group 15 form hydrides of the form EH3.

T/F

Answer 10

T

Question 11

Thermal stability, basicity,bond dissociation enthalpy, bond angle of hydrides of grp 15 _____ down the grp.

Answer 11

Decrease.

Reducing charac. Increases down the grp.

Question 12

Boiling point order for hydrides of grp 15 is

Answer 12

PH3

Question 13

Melting point order of grp 15 hydrides is

Answer 13

PH3

Question 14

Boiling point order of grp 15

Answer 14

N <p></p>

Question 15

Melting point order of grp 15 elements

Answer 15

N <p></p>

Question 16

Chile saltpeter is

Answer 16

NaNO3

Question 17

Indian saltpeter is

Answer 17

KNO3

Question 18

+3 oxi. State of __,__,__ become stable with respect to disproportionation. (Grp 15)

Answer 18

As, Bi, Sb

Question 19

Oxide in higher oxi. State are more stable than in lower oxi. State.
(T/F)

Answer 19

T

Question 20

Designate acidic, amphoteric, basic to oxides of grp 15 of the form E2O3.

Answer 20

N2O3 and P2O3 = purely acidic
As2O3 and Sb2O3 = amphoteric
Bi2O3 = predominately basic

Question 21

Give nature of N2O, NO, NO2

Answer 21

N2O & NO = neutral oxides

NO2 = mixed anhydride

Question 22

All trihalides except of ___ are unstable. (Grp 15)

Answer 22

N
Only NF3 is known to be stable.
Except BiF3 other trihalides are predominantly covalent.

Question 23

Except ___ all trihalides of grp 15 are predominantly covalent.

Answer 23

BiF3

Question 24

Preparation of dinitrogen

Answer 24

In laboratory,
NH4Cl + NaNO3 —> N2 + 2H2O + NaCl

Thermal decomposition of sodium/barium azide (for very pure N2),
Ba(N3)2 ——> Ba + 3N2
2NaN3 —-> 2Na + 3N2

{N3^-1 is k/a azide.}

Question 25

6Li + N2 —->

3Mg + N2 —->

Answer 25

2Li3N

Mg3N2

Question 26

At high temperature,

N2 + O2 —-> 2NO

Answer 26

True

Question 27

Preparation of ammonia

Answer 27

On small scale,
NH4Cl + Ca(OH)2 —->2NH3 + 2H2O + CaCl2

On large scale, by Haber’s process,
N2 + 3H2 ——>NH3 ΔH = -46.1 Kj/mol (exothermic)

Question 28

Optimum conditions for formation of ammonia are?

Answer 28

High pressure

Temperature ≈ 700K

Question 29

Cu^2+ (blue) + 4NH3 ——>

AgCl (white ppt.) + 2NH3 ——>

Answer 29

Cu^2+ (blue) + 4NH3 ——> [Cu(NH3)4]^2+ (deep blue)

AgCl (white ppt.) + 2NH3 ——> [Ag(NH3)2]Cl (colourless)

Question 30

NH3 is highly soluble in water.
Precipitates hydroxides of many metals from their salts.
Forms ammonium salt with acids.
Is a lewis base.

Which one of these is true?

Answer 30

All are true.

Question 31

Preparation of nitric acid?

Answer 31

In laboratory,
NaNO3 + H2SO4 ——> NaHSO4 + HNO3

On large scale by Ostwald’s process,
3 step process.

Question 32

Ostwald’s process ??

Answer 32

1) 4NH3 + 5O2 ——> 4NO + 6H2O. (In presence of Pt/Rh gauge catalyst)
2) 2NO + O2 ——>2NO2
3) 3NO2 + H2O ——> HNO3 + NO