12th Class Chemistry Chapter 4 Group V-A and VI-A Elements Short Question Answers
12th Class Chemistry Chapter 4 Group V-A and VI-A Elements Short Question Answers
| Class: | 12th Class | Subject: | Chemistry |
| Chapter: | Chapter 4 | Board: | All Boards |
Important Short Questions: This page contains solved short questions for 12th Class Chemistry Chapter 4. These questions are frequently asked in All Boards past papers. Memorize them for full marks.
12th Class Chemistry Chapter4 Group V-A and VI-A Elements Short Question Answers Given Below
1.What is the general occurrence of elements of group V-A?
Nitrogen occurs as N2 in the atmosphere 80% by volume.Phosphorus occurs in the form of its compounds as phosphates.Arsenic antimony and bismuth are less abundant.
2.How allotropy is associted with nitrogen and phosphorus?
Nitrogen has two allotropic forms in the solid states i.e. a-nitrogen and B-nitrogen. Phosphorus has six allotropic forms: i) White ii) Red iii) Scarlet iv) a-black iv) B-black vi) violet
3.How the melting and boiling points for the elements of group V-A vary down the group?
Melting points increase from upper to the downward direction except antimony and bismuth.Bismuth has lower melting point than antimony.
4.How the involvement of d-orbital increases the oxidation number of phosphorus?
Phosphorus has available d-orbitals in its outermost shell.Electrons can be promoted from s-orbital to this d-orbital and five unpaired electrons become avaiable.In this way it can show the valency of five.
5.Why the outermost p-sub-shells of group V-A elements are extra stable?
P-sub shell has three electrons in the outermost shell of group V-A.This is half-filled.The half-filled orbitals are extra stable.
6.What type of oxides are mostly given by the elements of group V-A?
The oxides having the general formulas M2O3 M2O4and M2O5 are given by the elements of group V-A Anyhow nitrogen can give N2O, and NO as additional oxides which are not given by other elements of this group.
7.Write down the formulas and names of oxyacids of nitrogen posphorus,arsenic and antimony with oxidation number +5?
These compounds are:
HNO3 Nitric acid
H3PO4 Phosphoric acid
H3AsO4 Aresenic acid
H3SbO4 Antimonic acid
HNO3 Nitric acid
H3PO4 Phosphoric acid
H3AsO4 Aresenic acid
H3SbO4 Antimonic acid
8.How does nitrogen differ from its family members in physical state atomicity and variety of oxidation states?
Nitrogen is a gas but other members are solids.Nitrogen is diatomic while others are tetratomic.Oxidation states of nitrogen are +1,+2,+3.+4,+5,-1,-2,-3 while other elements donot show the variety of oxidation states.
9.Write down the name formulae and colours of oxides of nitrogen along with the oxidation states of nitrogen in them?
Nitrogen give five oxides which are as follows:
N2O = Dinitrogen oxide +1(colourless)
NO = Nitrogen oxide +2(colourless)
N2O3 = Dinitrogen trioxide +3
N2O4 = Nitrogen dioxide +4(reddish brown)
N2O5 = Dinitrogen pentaoxide +5
N2O = Dinitrogen oxide +1(colourless)
NO = Nitrogen oxide +2(colourless)
N2O3 = Dinitrogen trioxide +3
N2O4 = Nitrogen dioxide +4(reddish brown)
N2O5 = Dinitrogen pentaoxide +5
10.How do you justify that N<sub>2</sub>O is a supporter of combustion?
N2O reacts with carbon sulphur;phosphorus magnesium sodium and copper to give their oxides and nitrogen gas is set free.
C+2N2O………………………. CO2 + 2N2
C+2N2O………………………. CO2 + 2N2
11.How do you compare the structures of N<sub>2</sub>O and NO?
N2O has a linear structure and shows resonance.The structure of NO exists in the form of a dimmer.
N=N+ – O–
N=N+ – O–
12.What is the rection of No with FeSO<sub>4</sub> solution?
NO reacts with FeSO4 to give a black compound.When this black compound is heated,NO gas is released
FeSO4 + NO………………..FeSO4.NO
Black ppt.
FeSO4 + NO………………..FeSO4.NO
Black ppt.
13.Justify that NO acts as an oxidizing agent?
No oxidizes SO2 to H2SO4.It oxidizes H2SO3 and H2S to S
2NO+So2+H2O………….H2SO4+N2O
H2S + 2NO……………. H2O + S+N2O
H2SO3+2NO……………… H2SO4+N2O
2NO+So2+H2O………….H2SO4+N2O
H2S + 2NO……………. H2O + S+N2O
H2SO3+2NO……………… H2SO4+N2O
14.How a brown couloured gas NO<sub>2</sub> is prepared from:<br /> i) pbNO<sub>3</sub> ii) Cu and HNO<sub>3</sub>
2Pb(NO3)2……………..2PbO+4NO2+O2
Cu+4HNO3………………. Cu(NO3)2 + 2NO2+2H2O
Cu+4HNO3………………. Cu(NO3)2 + 2NO2+2H2O
15.What is the effect of temperature on N<sub>2</sub>O<sub>4</sub>?
N2O4 is converted to NO through the following sequence of reactions.
N2O4…9ᵒC….N2O4….22ᵒC.. N2O4…140ᵒC…2NO2…620ᵒc..2NO+O2
Solid Liquid Vapours Gas Gaseous mixture
N2O4…9ᵒC….N2O4….22ᵒC.. N2O4…140ᵒC…2NO2…620ᵒc..2NO+O2
Solid Liquid Vapours Gas Gaseous mixture
16.How does NO<sub>2</sub> act as an oxidizing egent?
NO2 can oxidize H2S to S,CO to CO2 FeSO4 to Fe2(SO4)3 and KI to I2.
NO2+H2S…………………..NO+H2O+S
NO2+CO…………………..CO2+NO
NO2+2KI…………………. 2KNO2+I2.
NO2+H2S…………………..NO+H2O+S
NO2+CO…………………..CO2+NO
NO2+2KI…………………. 2KNO2+I2.
17.How does HNO<sub>2</sub> acts as an oxidizing agent?
HNO2 releases atomic oxygen which converts HI to I2,SO2 to H2SO4 SnCI2 to SnCI4 etc.
i) 2HNO2 + 2HI………………I2+2NO+2H2O
ii)2HNO2+SO2……………….H2SO4+2NO
iii)SnCI2+2HCI+2HNO2………………SnCI4+2NO+2H2O
i) 2HNO2 + 2HI………………I2+2NO+2H2O
ii)2HNO2+SO2……………….H2SO4+2NO
iii)SnCI2+2HCI+2HNO2………………SnCI4+2NO+2H2O
18.How does HNO<sub>2</sub> act as a reducing agent?
Certain strong oxidizing agents like acidified KmnO4,acidified K2Cr2O7 and H2O2 are reduced by HNO2.
HNO2+H2O2……………HNO3+H2O
HNO2+Br2+H2O…………2HBr+HNO3
2KmnO4+3H2SO4+5HNO2…………K2SO4+2MnSO4+5HNO3+3H2O
HNO2+H2O2……………HNO3+H2O
HNO2+Br2+H2O…………2HBr+HNO3
2KmnO4+3H2SO4+5HNO2…………K2SO4+2MnSO4+5HNO3+3H2O
19.Write down the reaction involved in the preparation on HNO<sub>3</sub> by Birckland Eyde’s process?
Reactions completes in four stages:
N2+O2…………………. 2NO
2NO+O2…………………2NO2
2NO2+H2O……………….HNO2+HNO3
3HNO2…………………….HNO3+2NO+H2O
N2+O2…………………. 2NO
2NO+O2…………………2NO2
2NO2+H2O……………….HNO2+HNO3
3HNO2…………………….HNO3+2NO+H2O
20.How dilute HNO<sub>3</sub> can be concentrated on commercial scale?
With concentrated H2SO4 68% HNO3 is converted into 98% HNO3.Water is absorbed by H2SO4.To get 100% HNO3 it is strongly cooled.Pure acid is deposited as colorless crystals at – 42ᵒC.These crystals are melted to get 100% HNO3.
21.Gives the reactions of HNO<sub>3</sub> in which it acts as an oxidizing agent?
HNO3 can oxidize FeSO4 H2S HI,SO2 and sugar.
6FeSO4+3H2SO4+2HNO3…………….. 3Fe2(SO4)3+2NO+4H2O
3H2S+2HNO3……………….2NO+3S+4H2O
SO2+2HNO3……………………H2SO4+2NO2
6FeSO4+3H2SO4+2HNO3…………….. 3Fe2(SO4)3+2NO+4H2O
3H2S+2HNO3……………….2NO+3S+4H2O
SO2+2HNO3……………………H2SO4+2NO2
22.What is aqua regia and how does it dissolve the noble metals?
When conc.HCI and conc.HNO3 are mixed in the ratio of 3:1 the mixture is called aqua regia.
HNO3+3HCI…………………2H2O+NOCI+CI2
Au+HNO3+3HCI…………….AuCI3+NO+2H2O
HNO3+3HCI…………………2H2O+NOCI+CI2
Au+HNO3+3HCI…………….AuCI3+NO+2H2O
23.What is meant by fuming nitric acid?
Concentrated nitric acid is a colourless volatile liquid and it fumes strongly in the air.Actually it evolves the NO2 gas.
24.Describe “Ring test for the confirmation of the presence of nitrate ions in solution?
Ring test is for NO–3 ion in aqueous solution.To the solution add freshly prepared solution of FeSO4.Then add a few drops of conc.H2SO4along the side of the test tube.A brown ring is produced.This is due to FeSO4 NO.
25.How does phosphorus occur in the form of minerals in plants and animal tissues?
The important ores of phosphorus are:
Ca3(PO4)2. = Phosphate rock
Ca3(PO4)2.CaCI2 = Chlorapatite
3Ca3(PO4)2.CaF2 = Fluorapatite
It also occurs in plants and animal tissues.Phosphorus is found in seeds,yolks of eggs nerves brain and bone marrow.
Ca3(PO4)2. = Phosphate rock
Ca3(PO4)2.CaCI2 = Chlorapatite
3Ca3(PO4)2.CaF2 = Fluorapatite
It also occurs in plants and animal tissues.Phosphorus is found in seeds,yolks of eggs nerves brain and bone marrow.
26.How do you compare the properties of white and red phosphorus?
White phosphorus is yellowish white substance and is a waxy solid.It is volatile in nature soluble in benzene and CS2.Its molecules are P4 and tetrahedral in shape.Red phosphorus is poisonous but less than that of white phosphorus.It is less reactive than white phosphorus.It exists in the form of tetrahedral P4 units to give macro molecules Red.P is prepared from white P in the presence of I2 or S as a catalyst and heating upto 250ᵒC.
27.How do you compare the structures of PCI<sub>3</sub> and NH<sub>3</sub>?
In both molecules the central atom is sp3-hybridized and they have lone pair at the fourth corner.They have pyramidal structures.Anyhow bond angles and bond lengths are different.
28.How PCI<sub>3</sub> and PCI<sub>5</sub> react with alcohols and carboxylic acids?
The phosphorus halides react with alcohols and carboxylic acids to give alkyl halides and acid halides
3ROH+PCI3……………..3RCI+H3PO3
ROH+PCI5…………….. RCI+POCI3.+HCI
3ROOH+PCI3……………..3RCOCI+H3PO3
RCOOH+PCI5………………ROCI+POCI3+HCI
3ROH+PCI3……………..3RCI+H3PO3
ROH+PCI5…………….. RCI+POCI3.+HCI
3ROOH+PCI3……………..3RCOCI+H3PO3
RCOOH+PCI5………………ROCI+POCI3+HCI
29.Give the names and formulas of various oxides of phosphorus?
Phosphorus gives four different types of oxides.
Phosphorus trioxide = P2O3 or P4O6
Phosphorus tetraoxide = P2O4
Phosphorus pentaoxide = P2O5
Phosphorus Peroxide = PO3Or P2O6
Phosphorus trioxide = P2O3 or P4O6
Phosphorus tetraoxide = P2O4
Phosphorus pentaoxide = P2O5
Phosphorus Peroxide = PO3Or P2O6
30..How does P<sub>2</sub>O<sub>3</sub> react with water in cold and hot state?
P2O3 reacts with water in cold state to give H3PO3.In hot state it gives H3PO4
P2O3+3H2O……..Cold/Hot………2H3PO3
2P2O3+6H2O…………….3H3PO4+PH3
31.How does P<sub>2</sub>O<sub>5</sub>. react with water in cold and hot state?
P2O5.+H2O……Cold……….2HPO3
P2O5.+2H2O…….Normal…H4P2O7.
P2O5.+3H2O……Hot………2H3PO4.
P2O5.+2H2O…….Normal…H4P2O7.
P2O5.+3H2O……Hot………2H3PO4.
32.Justify that P<sub>2</sub>O<sub>5</sub> is the dehyderating reagent?
P2O5.takes up water molecule from various compounds to give HPO3.
2HNO3+ P2O5……………….2HPO3+N2O5
H2SO4+ P2O5………………..2HPO3+SO3
2CH3COOH+ P2O5…………..(CH3CO)2O+2HPO3
C2H5OH+P2O5………………C2H4+2HPO3
2HNO3+ P2O5……………….2HPO3+N2O5
H2SO4+ P2O5………………..2HPO3+SO3
2CH3COOH+ P2O5…………..(CH3CO)2O+2HPO3
C2H5OH+P2O5………………C2H4+2HPO3
33.Give the name and formulas of oxyacids of phosphorus and indicate the oxidation number of phosphorus in them?
Some typical oxyacids of phosphorus are as follows:
i) Hypophosphorus acid = H3PO2 +1
ii) Phosphorus acid = H3PO3 +3
iii)Hypophosphoric acid = H4P2O6 +4
iv)Orthophosphoric acid = H3PO4 +5
i) Hypophosphorus acid = H3PO2 +1
ii) Phosphorus acid = H3PO3 +3
iii)Hypophosphoric acid = H4P2O6 +4
iv)Orthophosphoric acid = H3PO4 +5
34.H<sub>3</sub>PO<sub>3</sub> is dibasic acid although it has three hydrogen atoms in that.Give reasons?
The structure of H3PO3 shows that one of the hydrogens is directly connected with phosphorus which is not ionizable.So it does not release third hydrogen.Only two hydrogens are ionizable.
35.Give reactions to justify that H<sub>3</sub>PO<sub>3</sub> .is a reducing agent?
H3PO3 reduces CuSO4 .to copper metal AgNO3+NH4OH to silver metal.
CuSO4 . H3PO3+H2O…………….. H3PO4 H2SO4+Cu
H3PO3+ 2AgNO3+NH4OH………… H3PO42NH4NO3+H2O+2Ag
CuSO4 . H3PO3+H2O…………….. H3PO4 H2SO4+Cu
H3PO3+ 2AgNO3+NH4OH………… H3PO42NH4NO3+H2O+2Ag
36.How H<sub>3</sub>PO<sub>4</sub> is affected at high temperature?Is it a tribasic acid?
When H3PO4 is heated at 240ᵒC it given perphosphoric acid and on further heating it finally gives P2O5
2 H3PO4 ……. 240ᵒC…… H4PO7+H2O
H4P2O7…………316ᵒC……2HPO3+H2O
2HPO3…..600-700ᵒC……P2O5+H2O
Yes one mole of H3PO4 consumes three moles of NaOH.
37.How do you compare the elements of the group VI-A in their physical states?
Oxygen is a gas while other family members are solids.Anyhow their melting and boiling points increase down the group.P6 is a soft substance as compared to Te.
38.How sulphur can increase its oxidation number but oxygen can not?
Electronic distribution of sulphur shows that d-orbital is available for the promotion of electrons.So four and six upaired electrons can develop.In this way it increases its oxidation number as +4 and +6.
39.Mention various allotropic forms for the elements of group VI-A?
Oxygen has two non-metallic forms as O2 and O3 .Sulphur exists as rhombic monoclinic and plastic sulphur.Se has red and grey both are non-metallic.Te has two forms metallic and non metallic.Po has two metallic forms i.e.a and B.
40.How does oxygen differ from its own family members especially sulphur?
Oxygen has very small size and high electronegativity.d-orbitals are not available for the promotion of electrons.So oxidation number does not increase.Oxygen is highly electronegative as compared to sulphur.O2 is a gas at room temperature but sulphur is solid.
41.How does oxygen occur in nature?
It is a 44.6% of earth’s curst.25% of atmosphere by weight is free oxygen.Water contains 89% oxygen by weight.Chalk contains 48% oxygen while SiO2 has 53% of oxygen by weight.
42.How does sulphur occur in nature?
Sulphur occurs in the form of compounds like galena zinc blend cinabar copper pyrite and iron pyrites.The organic compounds and vegetables products like garlic mustard hair eggs and proteins sulphur in them.
43.Mention the catalytic condition for th emanufacture of H<sub>2</sub>SO<sub>4</sub> in contact process?
V2O5 or Fe2 O5 with the little amount of CuO can be used as catalyst.Anyhow Pt.metal supported on MgSO4 can also be used as a catalyst.
44.What are the optimum condition for the manufacture of H<sub>2</sub>SO<sub>4</sub> in the contact tower?
The temperature of 400-500ᵒC is maintained at a pressure of 1 atm.A suitable catalyst like V2O5 is used to increase the rate of reaction.
45.Give the advantages of contact process for the manufacture of sulpuric acid?
Contact process is superior to lead chamber process for the manufacture of H2SO4 due to following reasons:
i) A purified form of H2SO4 is prepared.
ii) Solid catlyst is used like V2O5 and Pt.while in the lead chamber process NO2 gas is used as a catalyst
i) A purified form of H2SO4 is prepared.
ii) Solid catlyst is used like V2O5 and Pt.while in the lead chamber process NO2 gas is used as a catalyst
46.Why SO<sub>3</sub> gas is dissovled in H<sub>2</sub>SO<sub>4 </sub> but not in water in contact process?
SO3 is dissolved in H2SO4 .If SO3 is dissolved directly in water then a large amount of heat is evolved.This heat gives a dense form of minute particles of H2SO4 .These particles do not easily condense down.
47.How does H<sub>2</sub>SO<sub>4 </sub>act as a dehydrating reagent?
H2SO4 has a strong affninity for water.It dehydrates oxalic acid formic acid ethyl alcohol glucose sucrose and starch.
48.Write down the equation for the reaction between conc. H<sub>2</sub>SO<sub>4 </sub>and copper and explain what type fo rection is it?
When concetrated H2SO4 in the cold state then no reaction takes place with copper.Anyhow when hot concentrated H2SO4 is reacted with Cu metal then SO2 gas evolves along with the formation of CuSO4 and H2O.
49.How KmnO<sub>4</sub> and K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> react with H<sub>2</sub>SO<sub>4 </sub>?
The reactions are as follows in which atomic oxygen is evolved:
2KMnO4+3 H2SO4 ……………. K2SO4 + 2MnSO4 + 3H2O+5[O]
K2Cr2O7+H2SO4…………………… K2SO4 +Cr2(SO4)3+4H2O +3[O]
2KMnO4+3 H2SO4 ……………. K2SO4 + 2MnSO4 + 3H2O+5[O]
K2Cr2O7+H2SO4…………………… K2SO4 +Cr2(SO4)3+4H2O +3[O]
50.Justify that H<sub>2</sub>SO<sub>4</sub>.is a king if chemicals?
H2SO4 is used in almost all the industries.Industrial development of a country can be best estimated from annual consumption of H2SO4.It is a barometer of industries.It is employed in:
i) Textile industry ii) Manufacture of fertilizers
iii)Medicine and chemicals iv) Process of electroplating.
i) Textile industry ii) Manufacture of fertilizers
iii)Medicine and chemicals iv) Process of electroplating.
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