hydfghfghfrogenfghfg

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Nishant Gupta, D-122, Prashant vihar, Rohini, Delhi-85

Contact: 9953168795, 9268789880

HYDROGEN

GUPTA CLASSES

For any help contact:

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HYDROGEN

Hydrogen is most abundant element in the universe. Major future source of energy.

Position of the hydrogen on the periodic table.Position of the hydrogen in the periodic table is uncertain. It may be placed above alkali metals in 1st column as well as above

halogens in the 17th column as it shows properties similar to both alkali metals and halogens.

1. Similarities with alkali metals.Like alkali metals hydrogen has one electron in the valence shell.

H = 1s1

Li = 1s2, 2s1

Na = [Ne] 3s1

2. Electro positive natureHydrogen has a tendency to lose electrons to give H+ ions.H2 2H

+ + 2e

When acidified water is electrolysed H2 is liberated at cathode similarly when molten salts of alkali metals are electrolysed

alkali metals are liberated at cathode.

3. Oxidation stateLike alkali metals hydrogen shows an oxidation state of +1

H+1Cl-1 Na+1Cl-1

4. Reducing AgentLike alkali metals hydrogen behaves as a strong reducing agent.

CuO + H2

Cu + H2O

B2O3+ 6K 3K2O + 2B

5. Formation of similar compounds with electronegative elements.HCl H2O H2S NaCl Na2O Na2S

Similarities with halogens1.Electronic configuration:Like halogens hydrogen has one electron less than nearest inert gas.2.Atomicity:Like halogens hydrogen is diatomic. H2, Cl2, Br2, I23.Non-metallic Nature:Like halogens hydrogen is a non-metal.4.Electronegative nature:When NaH, LiH, CaH2 (hydrides of strong electropositive elements) are electrolysed, hydrogen

is liberated at anode like halogens.

NaH = Na+

+ H

NaCl Na+

+ Cl

Cathode Na++ 1e Na Cathode Na++ 1e Na

Anode 2H

H2 + 2e Anode 2Cl

Cl2 + 2e

5.Oxidation state: In metal hydrides hydrogen like halogens shows an oxidation state of 1Na+1H1 Na+1Cl1

6.Ionization Enthalpy:Ionization enthalpy of hydrogen is comparable with halogens.7.Both halogens & hydrogen form similar compounds.

NaH CH4

NaCl CCl4

DIFFERENCE FROM ALKALI METALS1. Ionization enthalpy:Ionization enthalpy of hydrogen is much higher than alkali metals.2. Size & existence of H+:Unlike alkali metal ions H+ has a very small size and exists in aqueous solution as H9O4+ (H3O+)

ion.


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3. Unlike alkali metals hydrogen is a non-metallic diatomic gas.DIFFERENCE FROM HALOGENS.1. Less tendency to form hydride ions.2. Absence of unshared pair of electrons .3. Oxide of hydrogen H2O is neutral where as oxides of halogens are acidic in nature.ISOTOPES OF HYDROGENThere are three isotopes of hydrogen.

1. Protium or hydrogen H11

Atomic number = 1, Mass number = 1. It has one e and one proton. Only atom without neutron. Hydrogen contains

99.985% H11

.

2. Deuterium or Heavy hydrogen. H21

or D21

Atomic number = 1, Mass number = 2. Number of e= 1, p = 1, n = 1.

Naturally occurring hydrogen has 0.015% of D21

Tritium H31

or T31

. Radioactive isotope of hydrogen. It undergoes decay.

H3

1 He32 + e

1(10

16%)

Number of electron = 1, p = 1, n = 2

DIFF ERENCE IN PROPERTI ES OF I SOTOPES IS DUE TO ISOTOPIC EFFECT.

Preparation of Dihydrogen (H2)

1. Laboratory preparation.(a) By the reaction of granulated zinc with dilute hydrochloric acid.

Zn + 2HCl ZnCl2 + H2

(b) By the reaction of zinc with aqueous alkali.

Zn + 2NaOH Na2ZnO2 + H2

(Sodium zincate)

2. Commercial Production

(a) By electrolysis of acidified water using platinium electrodes.

2H2O (l) isElectrolys

2H2(g) + O2(g)

(b) By electrolysis of warm aqueous barium hydroxide solution between nickel electrodes

(c) by electrolysis of brine solution

NaCl Na+

+ Cl

Anode 2Cl

(aq) Cl2(g) + 2e

Cathode 2H2O (l) + 2e

H2(g) + 2OH

(aq)Overall reaction

2Na+ (aq) + 2Cl(aq) + 2H2O (l) Cl2(g) + H2(g) + 2Na+(aq) + 2OH(aq)

(e)Lanes Process: By passing steam overred hot iron.

3Fe (s) + 4H2O (g) K1070-820

Fe3O4 (s) + 4H2 (g)

(Magnetic Oxide)

(f)Uyenos Process: By treating aluminium scraps with KOH solution

2Al + 2KOH + 2H2O 2KAlO2 + 3 H2

(Potassium meta aluminate)


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(d) Reaction of steam on hydrocarbons or coke at high temperature in presence of catalyst.

CnH2n+2 + + nH2ONi

K1270

nCO + (3n+1) H2

CH4(g) + H2O (g)Ni

K1270

CO (g) + 3H2(g)

C (s) + H2O (g) K1270 CO (g) + H2 (g)Mixture of CO + H2 is called as water gas or synthesis gas or syn gas (Coal gasification)

CO (g) + H2O (g)ChromateIron

K673

CO2 (g) + H2 (g)

(Water gas shift reaction)

PROPERTIES

Physical propertiesColourless, odourless, tasteless, combustible gas lighter than air insoluble in water.

Chemical propertiesH2 has high bond enthalpy, so relatively inert at room temperature. Atomic hydrogen is produced at a high temperature in an

electric arc or under ultraviolet radiations.

1. Reaction with halogensH2 (g) + X2(g) 2HX (g) [X = F, Cl, Br, I]

Reactivity of halogens F2 > Cl2 > Br2 > I2

2. Reaction with oxygen

2H2 (g) + O2 (g) 2H2O (l), H = 285.9 KJ mol1

3. Reaction with nitrogen

3H2 (g) + N2 (g)673 , 200K atm

Fe 2NH3(g), H = 92.6 KJ mol

1

4. Reaction with metals

H2(g) + 2M (g) 2MH (g) [M = alkali metal]

Ca + H2 CaH2 (hydrolith)

5. Reaction with metal ions and metal oxides.

H2 (g) + Pd2+ (aq) Pd (s) + 2H+ (aq)

MxOy (s) + yH2 (g) xM (s) + yH2O

CuO (s) + H2(g) Cu (s) + H2O (g)6. Reaction with organic compounds(a) Hydrogenation of vegetable oil using nickel as catalyst to give edible fats (Vanaspati Ghee)(b) Hydroformylation of olefins give aldehydes.

H2+ CO + R CH CH2 RCH2CH2CHO

RCH2CH2CHO + H2 RCH2CH2CH2OH

USES OF DIHYDROGEN1. In synthesis of ammonia which is used in manufacture of Nitric acid and nitrogenous fertilizers.2. In manufacture of Vanaspati ghee.3. In manufacture of methanol4. In manufacture of metal hydrides.5. In preparation of hydrogen chloride.6. In metallurgical processes as a reducing agent.7. In atomic hydrogen torch (4000 K)8. In Oxyhydrogen torch.9. As a Rocket fuel.10. In fuel cells for generating electrical energy.


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HYDRIDESBinary compounds of hydrogen with other elements.

Types of hydrides1. Ionic or Saline hydrides2. Covalent or molecular hydrides3. Metallic or non-stoichiometric hydrides.

IONIC OR SALINE HYDRIDESFormed by strong electropositive elements ofS block.

But lighter metals form covalent hydrides like LiH, BeH2, MgH2. BeH2 and MgH2 are polymeric.Ionic hydrides are crystalline, non-volatile and nonconducting in solid state. But conduct electricity in molten state liberating

H2 (g) at anode.

2H Anode

H2 (g) + 2e

React violently with water producing H2 (g)

NaH (s) + H2O (aq) NaOH (aq) + H2 (g)CaH2 (s) + 2H2O (aq) Ca(OH)2 (aq) + 2H2 (g)

8LiH + Al2Cl6 2LiAlH4 + 6LiCl

(Lithium aluminium hydride)

2LiH + B2H6 2LiBH4 (Lithium Borohydride)

COVALENT OR MOLECULAR HYDRIDESCovalent hydrides are formed with most of P block elements. E.g. CH4, NH3, H2O HF. They are volatile hydrides.

1. Electron deficient hydrides: 13th column hydrides are electron deficient (B2H6). They are Lewis acids (central atomhas incomplete octet).

2. Electron precise hydrides:Have required number of electrons to write their Lewis structures (complete octet). E.gCH4, SiH4.

3. Electron rich hydrides: Have excess electrons present in the form of lone pairs. Elements in group 15 17 formsuch compounds (NH3 has 1 lone pair, H2O2 lone pairs, H F 3 lone pairs). They behave as Lewis bases. N, O

F hydrides forms H bonding showing relatively higher boiling point.

METALLIC OR NON-STOICHIOMETRIC OR INTERSTITIAL HYDRIDESFormed by many d-block & f-block elements. But metals of 7, 8, 9 groups do not form hydrides. Among elements of group

6 only Chromium forms CrH.

These hydrides conduct heat & electricity (less efficiently than parent metals). They are non stoichiometric.La H 2.87, Yb H2.55, Zr H1.3-1.75

V H0.56, Ni H0.6-0.7, Pd H 0.6-0.8

Except hydrides of Ni, Pd, Ce and Ac other hydrides have lattice different from that of parent metal. Metals like Pd, Pt canaccommodate very large volume of hydrogen (occlusion).

WATERHuman body has about 65% water. Some plants have as much as 95% water. It is colourless tasteless liquid. Water in liquid

& solid state show hydrogen bonding this leads to high boiling point, high freezing point, high heat of vapourisation and high

heat of fusion. Has higher specific heat, thermal conductance, surface tension & dipole moment & high dielectric constant. I

is a universal solvent.

STRUCTURE OF WATER AND ICE AS IN CHEMICAL BONDING.

Chemical properties1. Amphoteric nature

NH3 (aq) + H2O (l) OH(aq) + NH4

+ (aq)

H2S (aq) + H2O (l) H3O+ (aq) + HS(aq)

H2O (l) + H2O (l) H3O+

(aq) + OH

(aq)


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2. Redox reactions involving water.(a) Reduced to hydrogen by highly electropositive metals.

2H2O (l) + 2Na (s) 2NaOH (aq) + H2 (g)

During photosynthesis oxidized to O2.

6CO2 (g) + 12H2O (l) C6H12O6 (aq) + H2O (l) + 6O2 (g)

Fluorine oxidizes water to O2.2F2 + 2H2O (l) 4H

+ (aq) + 4F+ O2 (g)

3. Hydrolysis reactionDue to high dielectric constant it has a hydrating tendency.P4O10 (s) + 6H2O (l) 4H3PO4 (aq)

SiCl4 (l) + 2H2O (l) SiO2 (s) + 4HCl

N3(s) + 3H2O NH3 + 3OH

4. Hydrate formation[Cr(H2O)6]

3+, 3Cl

Coordinated water

BaCl2.2H2O Interstitial water

[Cu(H2O)4]2+ SO4

2. H2O hydrogen bonded water.

HARD & SOFT WATER

Soft water: Which gives lather with soap easily.Hard water: Does not give lather with soap.

Hardness of water is due to bicarbonates, chlorides and sulphates of calcium and magnesium. Hard water forms precipitate

with soap. Soaps are sodium & potassium salts of higher carboxylic acids like sodium stearate. Ca 2+/Mg2+ ions react with

sodium stearate to give precipitate of Ca/Mg stearate.

2C17H35COONa (aq) + Ca2+ (aq) [C17H35COO]2Ca + 2Na

+

Calcium stearate (PPT)

Temporary hardnessIt can be removed by boiling hard water. It is due to presence of bicarbonates of Ca/Mg.

Removal of temporary hardness

1. By Boiling: Bicarbonates decompose to give insoluble carbonates.Mg(HCO3)2

HeatingMgCO3 + H2O +CO2

Ca(HCO3)2

Heating

CaCO3

+ H2O +CO2

2. Clarks method: By adding calculated amount of lime to hard water.Ca(HCO3)2 + Ca(OH)2 2CaCO3 + 2H2O

Mg(HCO3)2 + Ca(OH)2 CaCO3 +MgCO3 + H2O

Permanent hardnessIt is due to soluble salts of Ca/Mg (chlorides and sulphates and can not be removed by boiling water.Removal of permanent hardness

1. Treatment with washing soda i.e. sodium carbonate. Washing soda reacts with chlorides and sulphates of Ca/Mg to giveinsoluble carbonates.

MCl2 + Na2CO3 MCO3 + 2NaCl

MSO4 + Na2CO3 MCO3 +Na2SO4 [M = Mg, Ca]

2. Calgon Process or Masking or Sequestration: Sodium hexametaphosphate (Na6P6O18) [Na2[Na4(PO3)6]] is known ascalgon. Ca

2+

and Mg2+

ions react with calgon to give soluble complex. Ca2+

and Mg2+

ion not free to react with soap.2Ca2+ + Na2[Na4(PO3)6]] Na2 [Ca2(PO3)6] + 2Na

+

2Mg2+ + Na2[Na4(PO3)6]] Na2 [Mg2(PO3)6] + 2Na+

3. Ion Exchange methods(a) Inorganic cation exchanger (permutit process) : These are hydrated sodium aluminium silicates Na2Al2 Si2O8xH2O also known as zeolites. These exchange Ca

2+and Mg

2+ions with Na

+ions.

Na2Z + M2+

M Z + 2Na+ [M = Ca or Mg]

(Sodium zeolite)


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After continuous use zeolites may be exhausted and can be regenerated by passing a solution of 10% NaCl through it.

MZ + 2NaCl Na2Z + MCl2

(b) Organic Exchangers (Deionization or demineralization of water)

(i) Cation exchanger: These are complex resins having acidic groups like CO2H or SO3H. When hard water is passed

through cation exchanger, all cation in water except H+ exchange with H+ ion of exchanger.

Ca2+ + 2H+Resin Ca(resin)2 + 2H+

Mg2+ + 2H+Resin Mg(resin)2 + 2H+(ii) Anion Exchanger: They are complex resins having NH3

+OH groups. When matter is passed through anion

exchanger all anions present in water exchange with OH ion of resin.

Cl+ OHResin Cl Resin + OH

SO42

+ 2OH

Resin SO42

(Resin)2 + 2OH

After some time ion exchanger may be exhausted and may be generated by passing conc. HCl through cation exchanger& passing NaOH solution through anion exchanger.

Ca(resin)2+ 2HCl CaCl2 + 2H+resin

Cl

resin + NaOH OH

resin + NaCl

HYDROGEN PEROXIDE (H2O2)

Preparation1. By acidifying barium peroxide and removing excess water by evaporation under reduced pressure.

BaO2. 8H

2O (s) + H

2SO

4(aq) BaSO

4(s) + H

2O

2(aq) + 8H

2O (l)

2. By electrolysis of 50% H2SO4. Electrolysis is carried out in a cell using platinum electrodes.H2SO4 H

+ + HSO4

At cathode 2H++ 2e H2

At anode 2HSO4 H2S2O8 +2e

Peroxydisulphuric acid

Peroxydisulphuric acid is distilled with water under pressure.

H2S2O8 + 2H2O H2O2 + 2H2SO4

3. From 2-Ethyl anthraquinol: It is dissolved in a mixture of benzene and cyclohexanol and air is passed through it.

In this case 1% H2O2 is obtained

Concentration of Hydrogen peroxide solution. Dilute solution of H2O2 is concentrated to 30% by distillation under reduced

pressure and further concentrated to 85% by distillation under low pressure. Then it is cooled in freezing mixture of solid

CO2 and ether when crystals of H2O2 separate out which are dried and remelted to give pure H2O2.

PropertiesH2O2 is a pale blue liquid, miscible with water forms hydrate H2O2. H2O. 30% solution of H2O2 is marketed as 100 volumes

H2O2.

Chemical properties

1. Decomposition: Decomposes on heating or long standing to give water and oxygen.2H2O2 2H2O + O2; H = 196.0 KJ.Decomposition is catalysed by finally divided Pt, MnO2, carbon, dust particles and rough surfaces. Decomposition is

suppressed by Glycerol, acetanilide or Phosphoric acid.

2. Acidic behaviour: It is a dibasic acid, neutralizes bases such as NaOH, Na2CO3.

2NaOH + H2O2 Na2O2 + 2H2O

Na2CO3 + H2O2 Na2O2 + H2O + CO2

3. Oxidising nature of H2O2


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In acidic medium: H2O2 +2H++ 2e 2H2O

Basic medium: H2O2 + 2e 2OH

In Acidic medium

(i) Oxidizes PbS to PbSO4

[H2O2 H2O + O] 4

PbS + 4O PbSO4---------------------------------

PbS + 4H2O2 PbSO4 + 4H2O

(ii) Oxidizes ferrous salt to ferric salts

2Fe2+

+ 2H+

+ H2O2 2Fe3+

+ 2H2O(iii) Oxidizes iodides to iodine

2I+ H2O2 + 2H+ I2 + 2H2O

(iv) Oxidizes ferrocyanide to ferricyanide

[Fe(CN)6]4+ 2H+ + H2O2 2[F2(CN)6]

2+ 2H2O

(v) Oxidizes Cr2O72to CrO5 which dissolves in ether to give blue colour.

Cr2O72+ 2H+ 4H2O2 2CrO5 + 5H2O

In basic medium

(i) Oxidizes Fe2+ to Fe3+

Fe2+ + H2O2 Fe3+ + 2OH

(ii) Oxidizes Mn2+

to Mn4+

Mn2+ + H2O2 Mn

4+ + 2OH

Reducing NatureH2O2 behaves as a reducing agent in acidic as well as basic medium.Acidic medium

H2O2 2H+ + O2 + 2e

(a) Reduces KMnO4 to colourless Mn2+

2MnO4+ 6H+ 5H2O2 2Mn

2+ + 8H2O + 5O2

(b) Reduce hypohalite to halides

HOCl + H2O2 H3O+ + Cl+ O2

(c) Reduces MnO2 to Mn2+

MnO2 + H2O2 + H2SO4 MnSO4 + 2H2O + O2

(d) Reduces moist Ag2O to Ag

H2O2 + Ag2O 2Ag + H2O + O2(e) Reduces O3 to O2

O3 + H2O2 H2O + 2O2(f) Reduces Cl2 to HCl

H2O2 + Cl2 2HCl + O2

Basic mediumH2O2 + 2OH

2H2O + O2 + 2e

(a) Reduces I2 to I

I2 + H2O2 + 2OH 2I+ 2H2O + O2

(b) Reduces KMnO4 to MnO2

2MnO4+ 3H2O2 2MnO2 + 3O2 + 2H2O + 2OH

(c) Reduces potassium ferricyanide to ferrocyanide

2[Fe(CN)6]3+ H2O2 + 2OH

2[Fe(CN)6]4+ 2H2O + O2

(d) Bleaching action: Bleaches delicate articles like Ivory, silk, feather wool etc. Bleaching action is due to oxidation ofcolouring material.

H2O2 H2O + O

Colouring matter + O Oxidized matter (colourless)

Storage of H2O2H2O2 is stored in wax lined glass or plastic bottles and kept in dark. Urea may be added as stabilizer.


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Structure of H2O2Each O atom is sp3 hybridized. H2O2 half open book like structure which is non-planar.

USES OF HYDROGEN PEROXIDE1. As a hair bleach and mild disinfectant.2. 30% H2O2 under the name perhydrol is used as antiseptic.3. In manufacture of sodium perborate and percarbonate used in high quality detergents.4. As a bleaching agent.5. In pollution control.

Test for H2O21. Turns moist starch-iodide paper blue.2. When ethereal solution of H2O2 is shaken with acidified solution of K2Cr2O7 blue colour is obtained in ether layer due

to formation of CrO5.

3. When acidified titanium salts are treated with H2O2, orange colour is produced.Ti4+ + H2O2 + 2H2O H2TiO4 + 4H

+

(orange)

Strength of H2O2

Equivalent weight =2

34

2

MassMolecular = 17

Volume strengthNumber of volumes of O2 at S.T.P. obtained by decomposition of one volume of H2O2 solution.

E.g. In 10 volume H2O2 One volume of H2O2 solution on complete decomposition given 10 volume of O2 at S.T.P.

Relation between Strength, Normality, Molarity and Volume strength.Let a solution of H2O2 be x volume. i.e. 1ml solution of H2O2 on decomposition gives x ml of O2 at S.T.P.

Volume of O2 at S.T.P. obtained from 1L i.e. 1000 ml of H2O2 solution will be 1000x ml.

2H2O2 (68g) 2H2O + O2 [22400 ml at S.T.P.]22400 ml of O2 at S.T.P. is obtained from= 68g H2O2

1 ml of O2 at S.T.P. is obtained from = g22400

68H2O2

And 1000x ml of O2 at S.T.P. is obtained from = x100022400

68 g H2O2

= x65

17

x422

68

Amount of H2O2 in gl1 =

65

strngthvolume17

Molarity (M) =34

StrengthVolume

6.5

17

M =2.11

StrengthVolume


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Volume strength = M 11.2

And Normality (N) =17

StrengthVolume

6.5

17

N =6.5

StrengthVolume

Volume strength = N 5.6

Ques: What is the meaning of 40 V H2O2? Calculate normality and molarity of 40 V H2O2?

HEAVY WATER (D2O)Heavy water is obtained by prolonged electrolysis of water. Used as a moderator in nuclear reactors.

PropertiesCaC2 + 2D2O C2D2 + Ca(OD)2

SO3 + D2O D2SO4

Al4C3 + 12D2O 3CD4 + 4Al(OD)3

Hydrogen as a fuel (Hydrogen Economy)It refers to use of hydrogen as an alternative source of energy as the calorific value in KJg1 is much higher than that of fossi

fuels

Some advantages of H2 used as a fuel are:

1.

It is abundantly available in the form of water.2. Will provide pollution free atmosphere as its combustion product is only water.3. Automobile engine will be 2550% more efficient than automobile engine using gasoline.4. Has high calorific value per gram.5. Time required for regeneration of hydrogen is much shorter.6. Hydrogen oxygen fuel cells provide other possibilities of powering motor vehicles.

Obstacles of Hydrogen Economy1. Availability of dihydrogen: Most likely source of hydrogen is water, it may be generated by using nuclear energy

or solar energy.

2. Storage & Transportation: Since H2 has explosive flammability which causes problem to its storage andtransportation. H2 can be stored in vacuum insulated cryogenic tanks. Liquid H2 can be transported by road or raitankers. Use of FeTi alloy which absorbs H2 by heating the alloy gives back H2.

3. Platinum scarcity: Pt is used in O2H2 fuel cells. Its scarcity is a problem. Liquid H2 is used as a rocket fuel.


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Assignment

1. Which of the following is used as a moderator in nuclear reactors?

(a) Hard water (b) Heavy water

(c) Deionized water (d) Mineral water

2. 30 volumes H2O2 means

(a) 30% H2O2 (b) 30cm

3

of the solution contains 1g of H2O2(c) 1cm3 of the solution liberates 30cm3 of O2 at STP

(d) 30cm3 of the solution contain one mole of H2O2

3. What is heavy water?

(a) H218O (b) H2

16O

(c) H2O3 (d) D2O

4. The volume strength of 1.5N H2O2 solution is(a) 4.8 (b) 5.2

(c) 8.8 (d) 8.4

5. Amongst H2O, H2S, H2Se and H2Te, the one with the highest boiling point is

(a) H2O because of hydrogen bonding

(b) H2Te because of higher molecular weight

(c) H2S because of hydrogen bonding

(d) H2Se because of lower molecular weight

6. Para and ortho hydrogen differ in

(a) atomic number (b) atomic mass(c) spins of protons (d) numberof neutrons

7. Heavy water is obtained by(a) boiling water (b) fractional distillation of H2O

(c) prolonged electrolysis of H2O (d) heating H2O2

8. Which one of the following processes will produce permanent hard water?

(a) Addition of Na2SO4 to water (b) Saturation of water with CaCO3

(c) Saturation of water with MgCO3 (d) Saturation of water with CaSO4

9. The reagent commonly used to determine hardness of water titrimetrically is

(a) Oxalic acid (b) Disodium salt of EDTA

(c) Sodium citrate (d) Sodium thiosulphate

10. What is false about H2O2?

(a) acts as both oxidizing and reducing agent(b) two OH bonds lie in the same plane

(c) pale blue liquid(d) can be oxidized by O3

11. The hardness of water sample containing 0.002 mole of magnesium sulphate dissolved in a litre of water is expressed

as:(a) 20 ppm (b) 200 ppm

(c) 2000 ppm (d) 120 ppm

12. When hydrogen peroxide is added to acidified potassium dichromate, a blue colour is produced due to formation of

(a) CrO3 (b) Cr2O3

(c) CrO5 (d) CrO42

13. In transforming 0.01 mole of PbS to PbSO4, the volume of 10 volume H2O2 required will be

(a) 11.2 mL (b) 22.4mL

(c) 33.6mL (d) 44.8mL14. Blackened oil painting can be restored into original form by the action of

(a) chlorine (b) BaO2

(c) H2O2 (d) MnO2

15. The strength of 10 volume H2O2 solution is

(a) 10 (b) 68

(c) 60.70 (d) 30.36

16. The metal which gives H2 on treatment with acid as well as NaOH is


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(a) Fe (b) Cu

(c) Zn (d) Hg

17. The oxide which gives H2O2 on treatment with dilute acid is

(a) PbO2 (b) TiO2

(c) MnO2 (d) Na2O2

18. The salt responsible for permanent hardness of H2O is(a) Na2SO4 (b) Mg(HCO3)2

(c) NaCl (d) MgCl2

19. Which of the following can produce hydrogen from water?

(a) Heated stannic oxide (b) Heated iron(c) Heated aluminium oxide (d) Heated copper oxide

20. H2 will not reduce which of the following oxide?

(a) Aluminium oxide (b) Calcium oxide

(c) Ferrous oxide (d) None of the above

Answers

1. (b) 2. (c) 3. (d) 4. (d) 5. (a) 6. (c) 7. (c) 8. (d) 9. (b) 10. (b)

11. (b) 12. (c) 13. (d) 14. (c) 15. (d) 16. (c) 17. (d) 18. (d) 19. (b) 20. (d)

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