2nd Year NotesChemistry class 12th

2nd Year CHEMISTRY CHAPTER 4 (Group VA and VIA Elements)

12th-Chemistry-CH-4

2 nd 2 nd 2^(“nd “)2^{\text {nd }}2nd Year CHEMISTRY CHAPTER 04 (Group VA and VIA Elements)

Short And Simple Questions And Answer:

Q1:Stify that conc. H2SO4 is a dehydrating agent.
Ans: H 2 S O 4 H 2 S O 4 H_(2)SO_(4)\mathrm{H}_{2} \mathrm{SO}_{4}H2SO4 has a great affinity for water because of high polarity, so it acts as dehydrating agent andeliminates water from different compounds.
(i) With oxalic acid it forms C O 2 C O 2 CO_(2)\mathrm{CO}_{2}CO2 and C o C o Co\mathrm{Co}Co.
C O O H C O O H COOH\mathrm{COOH}COOH
| C O O H conc. H 2 S O 4 C O 2 ( g ) + C O ( g ) + H 2 O ( I ) C O O H conc. H 2 S O 4 C O 2 ( g ) + C O ( g ) + H 2 O ( I ) |_(COOH)longrightarrow^(” conc. “H_(2)SO_(4))quadCO_(2)(g)+CO(g)+H_(2)O(I)\left.\right|_{\mathrm{COOH}} \stackrel{\text { conc. } \mathrm{H}_{2} \mathrm{SO}_{4}}{\longrightarrow} \quad \mathrm{CO}_{2}(\mathrm{~g})+\mathrm{CO}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(I)|COOH conc. H2SO4CO2( g)+CO(g)+H2O(I)
(ii) With formic acid, Co is formed.
H C O O H ( a q ) conc. H 2 S O 4 C O ( g ) + H 2 O ( I ) H C O O H ( a q ) conc. H 2 S O 4 C O ( g ) + H 2 O ( I ) HCOOH(aq)quadlongrightarrow^(” conc. “H_(2)SO_(4))quadCO(g)+H2O(I)\mathrm{HCOOH}(\mathrm{aq}) \quad \stackrel{\text { conc. } \mathrm{H}_{2} \mathrm{SO}_{4}}{\longrightarrow} \quad \mathrm{CO}(\mathrm{g})+\mathrm{H} 2 \mathrm{O}(I)HCOOH(aq) conc. H2SO4CO(g)+H2O(I)
(iii) With ethyl alcohol it forms ethylene.
C 2 H 5 O H 100 C conc. H 2 S O 4 C 2 H 4 + H 2 O C 2 H 5 O H 100 C conc. H 2 S O 4 C 2 H 4 + H 2 O C_(2)H_(5)OHquad100^(@)C^(” conc. “H_(2)SO_(4))quadC_(2)H_(4)+H_(2)O\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH} \quad \stackrel{\text { conc. } \mathrm{H}_{2} \mathrm{SO}_{4}}{100^{\circ} \mathrm{C}} \quad \mathrm{C}_{2} \mathrm{H}_{4}+\mathrm{H}_{2} \mathrm{O}C2H5OH100C conc. H2SO4C2H4+H2O
(iv) With wood, paper, sugar and starch it forms carbon and water.
C 6 H 12 O 6 conc. H 2 S O 4 6 C + 6 H 2 O C 12 H 22 O 11 conc. H 2 S O 4 12 C + 11 H 2 O ( C 6 H 10 O 5 ) n conc. H 2 S O 4 6 n C + 5 n H 2 O C 6 H 12 O 6      conc. H 2 S O 4      6 C + 6 H 2 O C 12 H 22 O 11      conc. H 2 S O 4      12 C + 11 H 2 O C 6 H 10 O 5 n      conc. H 2 S O 4      6 n C + 5 n H 2 O {:[C_(6)H_(12)O_(6),longrightarrow^(” conc. “H_(2)SO_(4)),6C+6H_(2)O],[C_(12)H_(22)O_(11),longrightarrow^(” conc. “H_(2)SO_(4)),12C+11H_(2)O],[(C_(6)H_(10)O_(5))n,longrightarrow^(” conc. “H_(2)SO_(4)),6nC+5nH_(2)O]:}\begin{array}{lll} \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} & \stackrel{\text { conc. } \mathrm{H}_{2} \mathrm{SO}_{4}}{\longrightarrow} & 6 \mathrm{C}+6 \mathrm{H}_{2} \mathrm{O} \\ \mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11} & \stackrel{\text { conc. } \mathrm{H}_{2} \mathrm{SO}_{4}}{\longrightarrow} & 12 \mathrm{C}+11 \mathrm{H}_{2} \mathrm{O} \\ \left(\mathrm{C}_{6} \mathrm{H}_{10} \mathrm{O}_{5}\right) \mathrm{n} & \stackrel{\text { conc. } \mathrm{H}_{2} \mathrm{SO}_{4}}{\longrightarrow} & 6 \mathrm{nC}+5 \mathrm{nH}_{2} \mathrm{O} \end{array}C6H12O6 conc. H2SO46C+6H2OC12H22O11 conc. H2SO412C+11H2O(C6H10O5)n conc. H2SO46nC+5nH2O

2. Name three allotropic forms of phosphorus.

Ans: The three allotropes of phosphorus
areWhite phosphorus
Red phosphorus
Black phosphorus

3. How does aqua regia dissolve gold?

Ans: When one volume of concentrated H N O 3 H N O 3 HNO3\mathrm{HNO} 3HNO3 is mixed with 3 volumes of concentrated H C l H C l HCl\mathrm{HCl}HCl, aqua regia is formed. It is employed to dissolve gold and platinum (Nobel metals).It contains nitrosyl chloride andchlorine gas.
H N O 3 (conc.) + 3 H C l ( conc. ) N O C l ( a q ) + C l 2 ( g ) + 2 H 2 O ( l ) H N O 3 (conc.) + 3 H C l ( conc. ) N O C l ( a q ) + C l 2 ( g ) + 2 H 2 O ( l ) HNO3″ (conc.) “+3HCl(” conc. “)quad longrightarrowquadNOCl(aq)+Cl2(g)+2H2O(l)\mathrm{HNO} 3 \text { (conc.) }+3 \mathrm{HCl}(\text { conc. }) \quad \longrightarrow \quad \mathrm{NOCl}(\mathrm{aq})+\mathrm{Cl} 2(\mathrm{~g})+2 \mathrm{H} 2 \mathrm{O}(\mathrm{l})HNO3 (conc.) +3HCl( conc. )NOCl(aq)+Cl2( g)+2H2O(l)
N O C l N O C l NOCl\mathrm{NOCl}NOCl formed is decomposed giving N O N O NO\mathrm{NO}NO and nascent C l C l Cl\mathrm{Cl}Cl
N O C l N O ( g ) + [ C l ] ( g ) N O C l N O ( g ) + [ C l ] ( g ) NOCllongrightarrowquadNO(g)+[Cl](g)\mathrm{NOCl} \longrightarrow \quad \mathrm{NO}(\mathrm{g})+[\mathrm{Cl}](\mathrm{g})NOClNO(g)+[Cl](g)
This liberated chlorine converts metals such as gold and platinum into their water soluble chlorides.
A u ( s ) + 3 [ C l ] ( a q ) 2 A u C l 3 ( a q ) A u ( s ) + 3 [ C l ] ( a q ) 2 A u C l 3 ( a q ) Au(s)+3[Cl](aq)quad longrightarrowquad2AuCl3(aq)\mathrm{Au}(\mathrm{s})+3[\mathrm{Cl}](\mathrm{aq}) \quad \longrightarrow \quad 2 \mathrm{AuCl} 3(\mathrm{aq})Au(s)+3[Cl](aq)2AuCl3(aq)
  1. How NO2 is prepared from: a. Lead nitrate b. C u + H N O 3 C u + H N O 3 Cu+HNO3\mathrm{Cu}+\mathrm{HNO} 3Cu+HNO3
It can be prepared in small quantities by heating lead nitrate.
2 P b ( N O 3 ) 2 ( s ) 2 P b O ( s ) + 4 N O 2 ( g ) + O 2 ( g ) 2 P b ( N O 3 ) 2 ( s ) 2 P b O ( s ) + 4 N O 2 ( g ) + O 2 ( g ) 2Pb(NO3)2(s)quad longrightarrowquad2PbO(s)+4NO2(g)+O2(g)2 \mathrm{~Pb}(\mathrm{NO} 3) 2(\mathrm{~s}) \quad \longrightarrow \quad 2 \mathrm{PbO}(\mathrm{s})+4 \mathrm{NO} 2(\mathrm{~g})+\mathrm{O} 2(\mathrm{~g})2 Pb(NO3)2( s)2PbO(s)+4NO2( g)+O2( g)
It can also be prepared by reacting conc. H N O 3 H N O 3 HNO3\mathrm{HNO} 3HNO3 with copper.
C u ( s ) + 4 H N O 3 (conc.) C u ( N O 3 ) 2 ( a q ) + 2 H 2 O ( l ) + 2 N O 2 ( g ) C u ( s ) + 4 H N O 3 (conc.) C u ( N O 3 ) 2 ( a q ) + 2 H 2 O ( l ) + 2 N O 2 ( g ) Cu(s)+4HNO3″ (conc.) “quad longrightarrowquadCu(NO3)2(aq)+2H2O(l)+2NO2(g)\mathrm{Cu}(\mathrm{s})+4 \mathrm{HNO} 3 \text { (conc.) } \quad \longrightarrow \quad \mathrm{Cu}(\mathrm{NO} 3) 2(\mathrm{aq})+2 \mathrm{H} 2 \mathrm{O}(\mathrm{l})+2 \mathrm{NO} 2(\mathrm{~g})Cu(s)+4HNO3 (conc.) Cu(NO3)2(aq)+2H2O(l)+2NO2( g)

5. How does HNO2 act as reducing agent?

Nitrous acid decolourizes acidified K M n O 4 K M n O 4 KMnO4\mathrm{KMnO} 4KMnO4 and bromine water. It readily gets oxidized to nitric acid, so it also behaves as a reducing agent.
2 K M n O 4 ( a q ) + 3 H 2 S O 4 ( a q ) + 5 H N O ( a q ) K 2 S O ( a q ) + 2 M n S O ( a q ) + 2 K M n O 4 ( a q ) + 3 H 2 S O 4 ( a q ) + 5 H N O ( a q ) K 2 S O ( a q ) + 2 M n S O ( a q ) + 2KMnO4(aq)+3H2SO4(aq)+5HNO(aq)quad longrightarrowK2SO(aq)+2MnSO(aq)+2 \mathrm{KMnO} 4(\mathrm{aq})+3 \mathrm{H} 2 \mathrm{SO} 4(\mathrm{aq})+5 \mathrm{HNO}(\mathrm{aq}) \quad \longrightarrow \mathrm{K} 2 \mathrm{SO}(\mathrm{aq})+2 \mathrm{MnSO}(\mathrm{aq})+2KMnO4(aq)+3H2SO4(aq)+5HNO(aq)K2SO(aq)+2MnSO(aq)+
3 H 2 O ( l ) + 5 H N O 2 ( a q ) 3 H 2 O ( l ) + 5 H N O 2 ( a q ) 3H2O(l)+5HNO2(aq)3 \mathrm{H} 2 \mathrm{O}(\mathrm{l})+5 \mathrm{HNO} 2(\mathrm{aq})3H2O(l)+5HNO2(aq)
H N O 2 ( a q ) + B r 2 ( a q ) + H 2 O ( I ) H N O 3 ( a q ) + 2 H B r ( a q ) H N O 2 ( a q ) + B r 2 ( a q ) + H 2 O ( I ) H N O 3 ( a q ) + 2 H B r ( a q ) HNO2(aq)+Br2(aq)+H2O(I)quad longrightarrowquadHNO3(aq)+2HBr(aq)\mathrm{HNO} 2(\mathrm{aq})+\mathrm{Br} 2(\mathrm{aq})+\mathrm{H} 2 \mathrm{O}(\mathrm{I}) \quad \longrightarrow \quad \mathrm{HNO} 3(\mathrm{aq})+2 \mathrm{HBr}(\mathrm{aq})HNO2(aq)+Br2(aq)+H2O(I)HNO3(aq)+2HBr(aq)

6. How does P205 react with water in cold and hot state?

With cold water phosphorus pentoxide forms metaphosporic acid.
P 2 O 5 ( s ) + H 2 O ( I ) 2 H P O 3 ( a q ) P 2 O 5 ( s ) + H 2 O ( I ) 2 H P O 3 ( a q ) P2O5(s)+H2O(I)quad longrightarrowquad2HPO3(aq)\mathrm{P} 2 \mathrm{O} 5(\mathrm{~s})+\mathrm{H} 2 \mathrm{O}(\mathrm{I}) \quad \longrightarrow \quad 2 \mathrm{HPO} 3(\mathrm{aq})P2O5( s)+H2O(I)2HPO3(aq)
With hot water, it forms orthophosphoric acid
P 2 O 5 ( s ) + 3 H 2 O ( l ) 2 H 3 P O 4 ( a q ) P 2 O 5 ( s ) + 3 H 2 O ( l ) 2 H 3 P O 4 ( a q ) P2O5(s)+3H2O(l)quad longrightarrowquad2H3PO4(aq)\mathrm{P} 2 \mathrm{O} 5(\mathrm{~s})+3 \mathrm{H} 2 \mathrm{O}(\mathrm{l}) \quad \longrightarrow \quad 2 \mathrm{H} 3 \mathrm{PO} 4(\mathrm{aq})P2O5( s)+3H2O(l)2H3PO4(aq)

7. Why S O 3 S O 3 SO3\mathrm{SO} 3SO3 is dissolved in sulphuric acid and not in water?

When S O 3 S O 3 SO3\mathrm{SO} 3SO3 is dissolved in 98 % H 2 S O 4 98 % H 2 S O 4 98%H2SO498 \% \mathrm{H} 2 \mathrm{SO} 498%H2SO4, we obtain Pyrosulphuric acid or (Oleum).
H 2 S O 4 ( a q ) + S O 3 ( g ) H 2 S 2 O 7 ( l ) H 2 S O 4 ( a q ) + S O 3 ( g ) H 2 S 2 O 7 ( l ) H2SO4(aq)+SO3(g)longrightarrowH2S2O7(l)\mathrm{H} 2 \mathrm{SO} 4(\mathrm{aq})+\mathrm{SO} 3(\mathrm{~g}) \longrightarrow \mathrm{H} 2 \mathrm{~S} 2 \mathrm{O} 7(\mathrm{l})H2SO4(aq)+SO3( g)H2 S2O7(l)
Oleum can be converted to sulphuric acid of any required concentration by adding water.
H 2 S 2 O 7 ( I ) + H 2 O ( I ) 2 H 2 S O 4 ( a q ) H 2 S 2 O 7 ( I ) + H 2 O ( I ) 2 H 2 S O 4 ( a q ) H2S2O7(I)+H2O(I)longrightarrow2H2SO4(aq)\mathrm{H} 2 \mathrm{~S} 2 \mathrm{O} 7(\mathrm{I})+\mathrm{H} 2 \mathrm{O}(\mathrm{I}) \longrightarrow 2 \mathrm{H} 2 \mathrm{SO} 4(\mathrm{aq})H2 S2O7(I)+H2O(I)2H2SO4(aq)
If S O 3 S O 3 SO3\mathrm{SO} 3SO3 is dissolved in water directly, a highly exothermic reaction occurs in which heat energy is released and it vaporizes suphuric acid to make mist or fog. This fog does not condense easily.
  1. Give two reactions which show oxidizing behaviour of NO.
H 2 S ( g ) + 2 N O ( g ) H 2 O ( g ) + N 2 O ( g ) + S ( s ) H 2 S O 3 ( a q ) + 2 N O ( g ) H 2 S O 4 ( a q ) + N 2 O ( g ) H 2 S ( g ) + 2 N O ( g )           H 2 O ( g ) + N 2 O ( g ) + S ( s ) H 2 S O 3 ( a q ) + 2 N O ( g )      H 2 S O 4 ( a q ) + N 2 O ( g ) {:[H2S(g)+2NO(g),longrightarrow,H2O(g)+N2O(g)+S(s)],[H2SO3(aq)+2NO(g),longrightarrowquadH2SO4(aq)+N2O(g)]:}\begin{array}{rlr} \mathrm{H} 2 \mathrm{~S}(\mathrm{~g})+2 \mathrm{NO}(\mathrm{g}) & \longrightarrow & \mathrm{H} 2 \mathrm{O}(\mathrm{g})+\mathrm{N} 2 \mathrm{O}(\mathrm{g})+\mathrm{S}(\mathrm{s}) \\ \mathrm{H} 2 \mathrm{SO} 3(\mathrm{aq})+2 \mathrm{NO}(\mathrm{g}) & \longrightarrow \quad \mathrm{H} 2 \mathrm{SO} 4(\mathrm{aq})+\mathrm{N} 2 \mathrm{O}(\mathrm{g}) \end{array}H2 S( g)+2NO(g)H2O(g)+N2O(g)+S(s)H2SO3(aq)+2NO(g)H2SO4(aq)+N2O(g)

9. Give two methods for the preparation of P C l 3 P C l 3 PCl3\mathrm{PCl} 3PCl3.

a. It is usually prepared by melting white phosphorus in a retort in an inert atmosphere of C O 2 C O 2 CO2\mathrm{CO} 2CO2 and current of dried chlorine is passed over it. The vapours of P C l 3 P C l 3 PCl3\mathrm{PCl} 3PCl3 are collected in a flask kept in ice-bath.
2 P ( s ) + 3 C l 2 ( g ) 2 P C l 3 ( I ) 2 P ( s ) + 3 C l 2 ( g ) 2 P C l 3 ( I ) 2P(s)+3Cl2(g)quad longrightarrowquad2PCl3(I)2 \mathrm{P}(\mathrm{s})+3 \mathrm{Cl} 2(\mathrm{~g}) \quad \longrightarrow \quad 2 \mathrm{PCl} 3(\mathrm{I})2P(s)+3Cl2( g)2PCl3(I)
b. It may also be prepared by the action of phosphorus with thionyl chloride.
2 P ( g ) + 4 S O C l 2 ( l ) 2 P C l 3 ( l ) + 2 S O 2 ( g ) + S 2 C l 2 ( s ) 2 P ( g ) + 4 S O C l 2 ( l ) 2 P C l 3 ( l ) + 2 S O 2 ( g ) + S 2 C l 2 ( s ) 2P(g)+4SOCl2(l)quad longrightarrowquad2PCl3(l)+2SO2(g)+S2Cl2(s)2 \mathrm{P}(\mathrm{g})+4 \mathrm{SOCl} 2(\mathrm{l}) \quad \longrightarrow \quad 2 \mathrm{PCl} 3(\mathrm{l})+2 \mathrm{SO} 2(\mathrm{~g})+\mathrm{S} 2 \mathrm{Cl} 2(\mathrm{~s})2P(g)+4SOCl2(l)2PCl3(l)+2SO2( g)+S2Cl2( s)
  1. Write two points of dissimilarities of oxygen and sulphur.
Oxygen Sulphur
Oxygen helps in combustion. Sulphur is itself combustible.
It is paramagnetic in nature. It is diamagnetic in nature.
Oxygen Sulphur Oxygen helps in combustion. Sulphur is itself combustible. It is paramagnetic in nature. It is diamagnetic in nature.| Oxygen | Sulphur | | :— | :— | | Oxygen helps in combustion. | Sulphur is itself combustible. | | It is paramagnetic in nature. | It is diamagnetic in nature. |

11. Why the elements of VIA other than oxygen show more than two oxidation states?

Show more than two oxidation states like 2 , + 2 , + 4 2 , + 2 , + 4 -2,+2,+4-2,+2,+42,+2,+4 and +6 because they have also d d ddd-subshells in their valence shells.

12.Give the names of four elements which do not react with nitric acid.

Gold, platinum, iridium and titanium do not react as they are noble metals and are not oxidized by nitric acid.

13. Explain the structure of H N O 2 H N O 2 HNO2\mathrm{HNO} 2HNO2 and HNO3.

The two important oxyacids of nitrogen, nitrous acid and nitric acid.
14.P205 is powerful dehydrating agent. Give two examples.
H 2 S O 4 ( a q ) + P 2 O 5 ( s ) S O 3 ( g ) + 2 H P O 3 ( a q ) 2 C H 3 C O O H ( a q ) + P 2 O 5 ( s ) ( C H 3 C O ) 2 O ( l ) + 2 H P O 3 ( a q ) Acetic anhydride H 2 S O 4 ( a q ) + P 2 O 5 ( s ) S O 3 ( g ) + 2 H P O 3 ( a q ) 2 C H 3 C O O H ( a q ) + P 2 O 5 ( s ) ( C H 3 C O ) 2 O ( l ) + 2 H P O 3 ( a q ) Acetic anhydride {:[H2SO4(aq)+P2O5(s),SO3(g)+2HPO3(aq)],[2CH3COOH(aq)+P2O5(s)longrightarrow(CH3CO)2O(l)+2HPO3(aq)],[” Acetic anhydride “]:}\begin{array}{cc} \mathrm{H} 2 \mathrm{SO} 4(\mathrm{aq})+\mathrm{P} 2 \mathrm{O} 5(\mathrm{~s}) & \mathrm{SO} 3(\mathrm{~g})+2 \mathrm{HPO} 3(\mathrm{aq}) \\ 2 \mathrm{CH} 3 \mathrm{COOH}(\mathrm{aq})+\mathrm{P} 2 \mathrm{O} 5(\mathrm{~s}) \longrightarrow(\mathrm{CH} 3 \mathrm{CO}) 2 \mathrm{O}(\mathrm{l})+2 \mathrm{HPO} 3(\mathrm{aq}) \\ \text { Acetic anhydride } \end{array}H2SO4(aq)+P2O5( s)SO3( g)+2HPO3(aq)2CH3COOH(aq)+P2O5( s)(CH3CO)2O(l)+2HPO3(aq) Acetic anhydride

15. Write any four uses of Nitric acid.

It is used:
  1. as a laboratory reagent.
  2. in the manufacture of nitrogen fertilizers.
  3. in the manufacture of explosives.
  4. for making varnishes and organic dyes.

16. What happens when NO2 is dissolved in water?

In the absence of air, it dissolves in water to form nitric and nitrous acids.
2 N O 2 ( g ) + H 2 O ( I ) H N O 3 ( a q ) + H N O 2 ( a q ) 2 N O 2 ( g ) + H 2 O ( I ) H N O 3 ( a q ) + H N O 2 ( a q ) 2NO2(g)+H2O(I)quad longrightarrowquadHNO3(aq)+HNO2(aq)2 \mathrm{NO} 2(\mathrm{~g})+\mathrm{H} 2 \mathrm{O}(\mathrm{I}) \quad \longrightarrow \quad \mathrm{HNO} 3(\mathrm{aq})+\mathrm{HNO} 2(\mathrm{aq})2NO2( g)+H2O(I)HNO3(aq)+HNO2(aq)
However in the presence of air or oxygen, nitric acid is the final product.
4 N O 2 ( g ) + 2 H 2 O ( l ) + O 2 ( g ) 4 H N O 3 ( a q ) 4 N O 2 ( g ) + 2 H 2 O ( l ) + O 2 ( g ) 4 H N O 3 ( a q ) 4NO2(g)+2H2O(l)+O2(g)quad longrightarrowquad4HNO3(aq)4 \mathrm{NO} 2(\mathrm{~g})+2 \mathrm{H} 2 \mathrm{O}(\mathrm{l})+\mathrm{O} 2(\mathrm{~g}) \quad \longrightarrow \quad 4 \mathrm{HNO} 3(\mathrm{aq})4NO2( g)+2H2O(l)+O2( g)4HNO3(aq)

17. Write two reactions of preparation of nitrous acid.

It can be prepared by dissolving dinitrogen trioxide in water at 0 o C 0 o C 0oC0 \mathrm{oC}0oC.
N 2 O 3 ( g ) + H 2 O ( l ) 2 H N O 2 ( a q ) N 2 O 3 ( g ) + H 2 O ( l ) 2 H N O 2 ( a q ) N2O3(g)+H2O(l)quad longrightarrowquad2HNO2(aq)\mathrm{N} 2 \mathrm{O} 3(\mathrm{~g})+\mathrm{H} 2 \mathrm{O}(\mathrm{l}) \quad \longrightarrow \quad 2 \mathrm{HNO} 2(\mathrm{aq})N2O3( g)+H2O(l)2HNO2(aq)
Pure nitrous acid solution can be prepared by reaction between ice cold barium nitrite solution and ice cold dilute sulphuric acid.
B a ( N O 2 ) 2 ( a q ) + H 2 S O 4 ( a q ) B a S O 4 ( a q ) + 2 H N O 2 ( a q ) B a ( N O 2 ) 2 ( a q ) + H 2 S O 4 ( a q ) B a S O 4 ( a q ) + 2 H N O 2 ( a q ) Ba(NO2)2(aq)+H2SO4(aq)quadBaSO4(aq)+2HNO2(aq)\mathrm{Ba}(\mathrm{NO} 2) 2(\mathrm{aq})+\mathrm{H} 2 \mathrm{SO} 4(\mathrm{aq}) \quad \mathrm{BaSO} 4(\mathrm{aq})+2 \mathrm{HNO} 2(\mathrm{aq})Ba(NO2)2(aq)+H2SO4(aq)BaSO4(aq)+2HNO2(aq)
  1. What is the action of heat on orthophosphoric acid? Write chemical equation also.
On heating, it loses water and converted into pyro and metaphosphoric acid.
Metaphosphoric
2 H 3 P O 4 2 H P O 3 2 H 3 P O 4 2 H P O 3 2H3PO4-2HPO32 \mathrm{H} 3 \mathrm{PO} 4-2 \mathrm{HPO} 32H3PO42HPO3
Orthophosphoric H4P2O7 3yrophosphoric
2H3PO4-2HPO3 Orthophosphoric H4P2O7 3yrophosphoric | $2 \mathrm{H} 3 \mathrm{PO} 4-2 \mathrm{HPO} 3$ | | | | | :—: | :—: | :—: | :—: | | Orthophosphoric | | H4P2O7 | 3yrophosphoric | | | | | |
acid acid acid

19. Write any four properties of sulphuric acid.

Properties of sulphuric acid are
(i) Pure sulphuric acid is a colourless oily liquid without an odour.
(ii) It dissolves in water liberating a lot of heat which raises the temperature of the mixture up to 120 o C 120 o C 120oC120 \mathrm{oC}120oC. H 2 S O 4 H 2 S O 4 H2SO4\mathrm{H} 2 \mathrm{SO} 4H2SO4 should always be poured in water in a thin stream to avoid any accident.
(iii) Pure acid is a nonconductor of electricity but the addition of a little water makes it a good conductor.
(iv) It is extremely corrosive to skin and causes very serious burns to all the tissues.

20. NO2 is a strong oxidizing agent. Prove with the help of two examples.

It is a strong oxidizing agent and oxidizes H 2 S H 2 S H2S\mathrm{H} 2 \mathrm{~S}H2 S to sulphur, ferrous sulphate to ferric sulphate etc.
H 2 S ( g ) + N O 2 ( g ) H 2 O ( l ) + S ( s ) + N O ( g ) 2 F e S O 4 ( a q ) + H 2 S O 4 ( a q ) + N O 2 ( g ) F e 2 ( S O 4 ) 3 ( a q ) + H 2 O ( l ) + N O ( g ) H 2 S ( g ) + N O 2 ( g ) H 2 O ( l ) + S ( s ) + N O ( g ) 2 F e S O 4 ( a q ) + H 2 S O 4 ( a q ) + N O 2 ( g ) F e 2 ( S O 4 ) 3 ( a q ) + H 2 O ( l ) + N O ( g ) {:[H2S(g)+NO2(g),H2O(l)+S(s)+NO(g)],[2FeSO4(aq)+H2SO4(aq)+NO2(g),longrightarrow,Fe2(SO4)3(aq)+H2O(l)+NO(g)]:}\begin{array}{lll} \mathrm{H} 2 \mathrm{~S}(\mathrm{~g})+\mathrm{NO} 2(\mathrm{~g}) & \mathrm{H} 2 \mathrm{O}(\mathrm{l})+\mathrm{S}(\mathrm{s})+\mathrm{NO}(\mathrm{g}) \\ 2 \mathrm{FeSO} 4(\mathrm{aq})+\mathrm{H} 2 \mathrm{SO} 4(\mathrm{aq})+\mathrm{NO} 2(\mathrm{~g}) & \longrightarrow & \mathrm{Fe} 2(\mathrm{SO} 4) 3(\mathrm{aq})+\mathrm{H} 2 \mathrm{O}(\mathrm{l})+\mathrm{NO}(\mathrm{g}) \end{array}H2 S( g)+NO2( g)H2O(l)+S(s)+NO(g)2FeSO4(aq)+H2SO4(aq)+NO2( g)Fe2(SO4)3(aq)+H2O(l)+NO(g)

21. Give two reactions of sulphuric acid which show its oxidizing behaviour.

H2SO4 acts as strong oxidizing agent.
(i) It oxidizes C C C\mathrm{C}C and S S S\mathrm{S}S giving C O 2 C O 2 CO2\mathrm{CO} 2CO2 and S O 2 S O 2 SO2\mathrm{SO} 2SO2, respectively.
C ( s ) + 2 H 2 S O 4 ( a q ) C O 2 ( g ) + 2 S O 2 ( g ) + 2 H 2 O ( g ) S ( s ) + 2 H 2 S O 4 ( a q ) 3 S O 2 ( g ) + 2 H 2 O ( l ) C ( s ) + 2 H 2 S O 4 ( a q ) C O 2 ( g ) + 2 S O 2 ( g ) + 2 H 2 O ( g ) S ( s ) + 2 H 2 S O 4 ( a q ) 3 S O 2 ( g ) + 2 H 2 O ( l ) {:[C(s)+2H2SO4(aq),CO2(g)+2SO2(g)+2H2O(g)],[S(s)+2H2SO4(aq),longrightarrow,3SO2(g)+2H2O(l)]:}\begin{array}{lll} \mathrm{C}(\mathrm{s})+2 \mathrm{H} 2 \mathrm{SO} 4(\mathrm{aq}) & \mathrm{CO} 2(\mathrm{~g})+2 \mathrm{SO} 2(\mathrm{~g})+2 \mathrm{H} 2 \mathrm{O}(\mathrm{g}) \\ \mathrm{S}(\mathrm{s})+2 \mathrm{H} 2 \mathrm{SO} 4(\mathrm{aq}) & \longrightarrow & 3 \mathrm{SO} 2(\mathrm{~g})+2 \mathrm{H} 2 \mathrm{O}(\mathrm{l}) \end{array}C(s)+2H2SO4(aq)CO2( g)+2SO2( g)+2H2O(g)S(s)+2H2SO4(aq)3SO2( g)+2H2O(l)
(ii) H 2 S H 2 S H2S\mathrm{H} 2 \mathrm{~S}H2 S is oxidized to S S S\mathrm{S}S.
H 2 ( s ) + H 2 S O 4 ( a q ) S ( s ) + S O 2 ( g ) + 2 H 2 O ( g ) H 2 ( s ) + H 2 S O 4 ( a q ) S ( s ) + S O 2 ( g ) + 2 H 2 O ( g ) H2(s)+H2SO4(aq)longrightarrowS(s)+SO2(g)+2H2O(g)\mathrm{H} 2(\mathrm{~s})+\mathrm{H} 2 \mathrm{SO} 4(\mathrm{aq}) \longrightarrow \mathrm{S}(\mathrm{s})+\mathrm{SO} 2(\mathrm{~g})+2 \mathrm{H} 2 \mathrm{O}(\mathrm{g})H2( s)+H2SO4(aq)S(s)+SO2( g)+2H2O(g)

22. Give four dissimilarities of oxygen and sulphur. DISSIMILARITIES

Oxygen Sulphur
1.
Allotropic
forms
Allotropic forms| Allotropic | | :— | | forms |
There are two allotropic form of oxygen
O2and O3
There are two allotropic form of oxygen O2and O3| There are two allotropic form of oxygen | | :— | | O2and O3 |
There are 3 allotropic forms of sulphur i.e.
rhombic, monoclinic and plastic sulphur.
There are 3 allotropic forms of sulphur i.e. rhombic, monoclinic and plastic sulphur.| There are 3 allotropic forms of sulphur i.e. | | :— | | rhombic, monoclinic and plastic sulphur. |
2.
Physical
states
Physical states| Physical | | :— | | states |
It is gas at ordinary temperature. It is solid at ordinary temperature.
3.
Water
solubility
Water solubility| Water | | :— | | solubility |
Oxygen is sparingly soluble in water. Sulphur is not soluble in water.
4.
Reaction
with water
Reaction with water| Reaction | | :— | | with water |
It does not react with water.
When stem is passed through boiling sulphur a
little hydrogen sulphide and sulphur dioxide are
formed.
When stem is passed through boiling sulphur a little hydrogen sulphide and sulphur dioxide are formed.| When stem is passed through boiling sulphur a | | :— | | little hydrogen sulphide and sulphur dioxide are | | formed. |
Oxygen Sulphur 1. “Allotropic forms” “There are two allotropic form of oxygen O2and O3” “There are 3 allotropic forms of sulphur i.e. rhombic, monoclinic and plastic sulphur.” 2. “Physical states” It is gas at ordinary temperature. It is solid at ordinary temperature. 3. “Water solubility” Oxygen is sparingly soluble in water. Sulphur is not soluble in water. 4. “Reaction with water” It does not react with water. “When stem is passed through boiling sulphur a little hydrogen sulphide and sulphur dioxide are formed.”| | | Oxygen | Sulphur | | :— | :— | :— | :— | | 1. | Allotropic <br> forms | There are two allotropic form of oxygen <br> O2and O3 | There are 3 allotropic forms of sulphur i.e. <br> rhombic, monoclinic and plastic sulphur. | | 2. | Physical <br> states | It is gas at ordinary temperature. | It is solid at ordinary temperature. | | 3. | Water <br> solubility | Oxygen is sparingly soluble in water. | Sulphur is not soluble in water. | | 4. | Reaction <br> with water | It does not react with water. | When stem is passed through boiling sulphur a <br> little hydrogen sulphide and sulphur dioxide are <br> formed. |

23. What is aqua regia?

Aqua regia is a mixture of 3 parts of conc. H C l H C l HCl\mathrm{HCl}HCl and one part of conc. H N O 3 H N O 3 HNO_(3)\mathrm{HNO}_{3}HNO3. Metals like gold and platinum can dissolve in aqua regia by the formation of their chlorides
3 H C l + H N O 3 N O C l + C l 2 + 2 H 2 O 2 N O C l 2 N O + C l 2 3 H C l + H N O 3 N O C l + C l 2 + 2 H 2 O 2 N O C l 2 N O + C l 2 {:[3HCl+HNO_(3)longrightarrowNOCl+Cl_(2)+2H_(2)O],[2NOCllongrightarrow2NO+Cl_(2)]:}\begin{gathered} 3 \mathrm{HCl}+\mathrm{HNO}_{3} \longrightarrow \mathrm{NOCl}+\mathrm{Cl}_{2}+2 \mathrm{H}_{2} \mathrm{O} \\ 2 \mathrm{NOCl} \longrightarrow 2 \mathrm{NO}+\mathrm{Cl}_{2} \end{gathered}3HCl+HNO3NOCl+Cl2+2H2O2NOCl2NO+Cl2
This liberated chlorine converts noble metals to their chlorides.
2 A u + 3 C l 2 2 A u C l 3 2 A u + 3 C l 2 2 A u C l 3 2Au+3Cl_(2)longrightarrow2AuCl_(3)2 \mathrm{Au}+3 \mathrm{Cl}_{2} \longrightarrow 2 \mathrm{AuCl}_{3}2Au+3Cl22AuCl3
Over all reaction is as follows:
2 A l + 3 H C l + H N O 3 A u C l 3 + N O + 2 H 2 O 2 A l + 3 H C l + H N O 3 A u C l 3 + N O + 2 H 2 O 2Al+3HCl+HNO_(3)longrightarrowAuCl_(3)+NO+2H_(2)O2 \mathrm{Al}+3 \mathrm{HCl}+\mathrm{HNO}_{3} \longrightarrow \mathrm{AuCl}_{3}+\mathrm{NO}+2 \mathrm{H}_{2} \mathrm{O}2Al+3HCl+HNO3AuCl3+NO+2H2O

24. Justify that sulphuric acid is king of chemicals.

It is called king of acid because of its direct and indirect applications in manufacture of many chemicals including fertilisers. Sulphuric acid is used to clean up rust from steel rolls and soap. It also dissolves its own compounds. It replaces salts from weaker acids. It is ideal to call sulphuric acid as king of chemicals .It is corrosive acts as good dehydrant.

25. Justify that NO acts as an oxidizing agent?

H 2 S ( g ) + 2 N O ( g ) H 2 O ( g ) + N 2 O ( g ) + S ( s ) H 2 S O 3 ( a q ) + 2 N O ( g ) H 2 S O 4 ( a q ) + N 2 O ( g ) H 2 S ( g ) + 2 N O ( g ) H 2 O ( g ) + N 2 O ( g ) + S ( s ) H 2 S O 3 ( a q ) + 2 N O ( g ) H 2 S O 4 ( a q ) + N 2 O ( g ) {:[H_(2)S(g)+2NO(g)longrightarrow,H_(2)O(g)+N_(2)O(g)+S(s)],[H_(2)SO_(3)(aq)+2NO(g),longrightarrowquadH_(2)SO_(4)(aq)+N_(2)O(g)]:}\begin{array}{ll} \mathrm{H}_{2} \mathrm{~S}(\mathrm{~g})+2 \mathrm{NO}(\mathrm{g}) \longrightarrow & \mathrm{H}_{2} \mathrm{O}(\mathrm{g})+\mathrm{N}_{2} \mathrm{O}(\mathrm{g})+\mathrm{S}(\mathrm{s}) \\ \mathrm{H}_{2} \mathrm{SO}_{3}(\mathrm{aq})+2 \mathrm{NO}(\mathrm{g}) & \longrightarrow \quad \mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq})+\mathrm{N}_{2} \mathrm{O}(\mathrm{g}) \end{array}H2 S( g)+2NO(g)H2