CLS Aipmt 17 18 XI Che Study Package 3 SET 2 Chapter 9

Chapter

9

Hydrogen Solutions

SECTION - A

Objective Type Questions 1.

The ionis ionisatio ation n energy energy of hydro hydrogen gen is high as as compare compared d to alkali alkali metal metals s because because of (1) One electron in outermost shell

(2)

Small size

(3) One proton in its nucleus

(4)

No neutron

Sol. Answer (2) The ionisation energy of hydrogen is very high in comparison to alkali metals. This is because the 1s electron of hydrogen is tightly held by the nucleus due to its small size.

iH of hydrogen = 1312 kJ mol–1. 2.

Which Wh ich of the the foll follow owing ing is the the cor correc rectt state stateme ment? nt? (1)) Hydrogen has the same I.E. (1 I.E. as that that of alkali metals metals (2)) Hydrogen has (2 has strong tendency tendency to gain gain one electron electron same as that of alkali alkali metals (3)) Hydrogen molecule is diatomic (3 diatomic so are the the halogens halogens (4)) Electron affinity of hydrogen (4 hydrogen is same same as that that of halogens halogens

Sol. Answer (3) Hydrogen molecule is diatomic so are the halogens. Resemblance with halogens, hydrogen molecule is diatomic (H2) and so are the molecules of halogens (say F2). 3.

The Th e isot isotop ope e of hyd hydro rogen gen wh which ich is rad radioa ioact ctiv ive e is (1) Protium

(2)

Tritium

(3)

Deuterium

(4)

Neutron

Sol. Answer (2)



3 1

H or T

 : This isotope of hydrogen is radioactive and emits low energy  particles having half life period of –

12.33 years. 4.

Hydrogen Hydr ogen accept accepts s an electro electron n to attain attain inert inert gas gas configu configurati ration. on. In this way way it resemb resembles les (1) Halogens

(2)

Alkali metals

(3)

Transition metals

(4)

Chalcogens

Sol. Answer (1) Halogens with general outer electronic configuration (ns2np5) have a tendency to gain one electron and attain nearest noble gas configuration. Similarly, hydrogen (1s1) gains one electron to form H– ion and attain nearest noble gas (helium gas) configuration. Aakash Educational Services Pvt. Ltd.

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5.

Hydrogen

Solution of Assignment (Set-2)

Hydrog Hyd rogen en acts acts as as a redu reducin cing g agent agent and and thus thus res resemb embles les (1) Halogen

(2)

Noble gas

(3)

Radioactive elements

(4)

Alkali metals

Sol. Answer (4) Alkali metals have a strong tendency to lose one electron from their outermost shell to form unipositive ions (Li+, Na+, K+, Rb+, Cs+) and attain nearest noble gas configuration. Similarly, hydrogen also loses electron to form H+ ion. Reducing agent undergoes oxidation and oxidation means the loss of electrons by the element. 6.

Which Whi ch posi positio tion n of hydr hydrog ogen en expla explain in its its prope propert rties ies? ? (1) At the top of halogens

(2)

At the top of alkali metals

(3) At the top of chalcogens

(4)

Both (1) & (2)

Sol. Answer (4) The electronic configuration of hydrogen is 1s1, yet its position in the periodic table is not certain and unsatisfactory. Hydrogen exhibits properties similar to both alkali metals (group 1) and halogens (group 17). 7.

Ioni Io nisa sati tion on en ener ergy gy of hy hydr drog ogen en is (1)) Equ (1 Equal al to tha thatt of fluo fluorine rine (2)) Low (2 Lower er than than that that of fluor fluorine ine (3)) Slig (3 Slightly htly higher higher than than that that of fluorine fluorine (4)) Muc (4 Much h higher higher than than that that of fluori fluorine ne

Sol. Answer (2)

iH of hydrogen (1312 kJ mol–1) is lower than iH of fluorine (1680 kJ mol–1). 8.

Which Whic h of the follow following ing statem statements ents concer concerning ning protiu protium, m, deuteri deuterium um and tritiu tritium m is not true? true? (1)) The (1 They y are isotop isotopes es of each each other other (2)) They have similar (2 similar electr electronic onic configur configurations ations (3)) They exist in the nature (3 nature in the ratio of 1 : 2 : 3 respectively respectively (4)) Their mass (4 mass numbers are are in the ratio 1 : 2 : 3 respectively respectively

Sol. Answer (3) They exist in the nature in the ratio of 1 : 2 : 3 respectively. The statement is incorrect as their mass numbers are in the ratio 1 : 2 : 3 respectively. 9.

The Th e num numbe berr of of nuc nucle leon ons s in in D2 molecule is (1) 1

(2)

2

(3)

3

(4)

4

Sol. Answer (4) Deuterium has one proton and one neutron in the nucleus, 12 H or D  . Therefore, in ‘D2’ there are a total of four nucleons i.e. 2 protons + 2 neutrons = 4 nucleons. 10. Wa Watter gas is (1) CO + H2

(2)

CO2 + H 2

(3)

CO + H2O

(4)

CO2 + N 2

Sol. Answer (1) K      CO(g) + H 2(g) C(s) + H 2O(g)  1270

Water gas Aakash Educational Services Pvt. Ltd.



Hydrogen

49

11. The catalyst used in the water-gas shift reaction is (1) Sodium arsenite

(2)

Nickel

(3) Potassium permanganate

(4)

Iron chromate

Sol. Answer (4) 673 K CO(g) + H 2O(g)   CO 2 (g) + H 2(g) FeCrO 4

Iron chromate

12. The reaction between which of the following reactants produces hydrogen? (1) Zn + HCl

(2)

BaO2 + HCl

(3)

K2S2O8 + H2O

(4)

Na2O2 + HCl

Sol. Answer (1) In laboratory dihydrogen is prepared by the reaction of granulated zinc with dilute HCl or dilute H2SO4. 13. High purity dihydrogen is obtained by electrolysing (1) Warm aqueous barium hydroxide

(2)

Brine solution

(3) Acidified sulphate solution

(4)

Water gas

Sol. Answer (1) Hydrogen of high purity (> 99.95%) is obtained by electrolysing warm aqueous barium hydroxide between nickel electrodes. 14. Hydrogen is not obtained when sodium reacts with (1) Cold water

(2)

Dilute H2SO4

(3)

Molten NaCl

(4)

Dilute HCl

Sol. Answer (3) For the liberation of hydrogen as the product, any compound containing hydrogen should be present in the reactants. 15. The process by which ammonia is formed from nitrogen and hydrogen is (1) Contact process

(2)

Haber process

(3)

Ostwald process

(4)

Hydrogenation process

(4)

Carboxylic acids

Sol. Answer (2) 673 K, 200 atm   2NH3 (g); H = –92.6 kJ mol –1 3H2 (g) + N 2 (g)  Fe

16. Hydrogenation of alkenes yield (1) Alkanes

(2)

Alkynes

(3)

Aldehydes

(1) Good conductors of electricity in solid state

(2)

Stoichiometric compounds

(3) Volatile

(4)

Non-crystalline

Sol. Answer (1) H

H

H C C H(g) + H (g) Ethene

473 K

2

Ni

H C – CH (g) Ethane 3

3

The above reaction is called catalytic hydrogenation. 17. Ionic hydrides are usually

Sol. Answer (2) The ionic hydrides are stoichiometric which are formed when hydrogen combines with elements of s-block which are highly electropositive in nature. Aakash Educational Services Pvt. Ltd.


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Hydrogen


18. Group 2 hydrides with significant covalent character is/are (1) BeH2

(2)

MgH2

(3)

CaH2

(4)

Both (1) & (2)

Sol. Answer (4) There are some elements in s-block like Be, Mg which do not form ionic hydrides. Due to the small size and high electronegativity (high polarising power). 19. In which of the following compounds does hydrogen has an oxidation state of –1? (1) CH4

(2)

NH3

(3)

HCl

(4)

CaH2

Sol. Answer (4) Ionic hydrides are formed by transfer of electrons from metal to hydrogen atoms and contains hydrogen as H– ion such as calcium hydride (Ca2+2H–). 20. The H – O – H angle in water molecule is about (3)

109°28

(1) Treating with washing soda

(2)

Boiling

(3) Adding calgon

(4)

Addition of chlorine

(1) 90°

(2)

180°

(4)

104.5°

Sol. Answer (4) O (Water molecule)

104.5 ° H

H

21. Hardness of water cannot be removed by

Sol. Answer (4) Hardness of water cannot be removed by addition of chlorine because chlorine is not a water softening agent. 22. Temporary hardness may be removed from water by adding (1) CaCO3

(2)

Ca(OH)2

(3)

CaSO4

(4)

HCl

Sol. Answer (2) Clark's method:

 2CaCO 3  + 2H 2O Ca(HCO 3 ) 2 + Ca(OH) 2   2CaCO 3  + Mg(OH) 2  + 2H 2O Mg(HCO 3 ) 2 + 2Ca(OH) 2  23. Permanent hardness of water is due to the presence of (1) Sulphates of Mg and Ca

(2)

Bicarbonates of Mg and Ca

(3) Sulphates of Na and K

(4)

Bicarbonates of Na and K

Sol. Answer (1) Permanent hardness of water is due to the presence of chlorides and sulphates of calcium and magnesium. 24. Permanent hardness of water is removed by adding (1) Slaked lime

(2)

Sodium bicarbonate

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(3)

Washing soda

(4)

Calcium hydroxide



Hydrogen

51

Sol. Answer (3) CaCl 2 + Na 2CO 3



CaCO 3



+ 2NaCl

ppt

 MgCO 3  + Na 2SO 4 MgSO 4 + Na 2CO 3  ppt

When calculated amount of washing soda is added to hard water containing soluble sulphates and chlorides of calcium and magnesium, then these soluble salts get converted into insoluble carbonates which get precipitated. 25. Permutit is chemically (1) Hydrated sodium aluminium silicate

(2)

Sodium hexaphosphate

(3) Sodium bicarbonate

(4)

Calcium hydroxide

Sol. Answer (1) Ion exchange method employs the use of zeolite or permutit which is hydrated sodium aluminium silicate (NaAlSiO4) therefore, it is also known as zeolite/permutit process. 26. In Clark’s process for removing hardness of water, the reagent used is (1) Acidic

(2)

Basic

(3)

Neutral

(4)

Both (1) & (2)

Sol. Answer (2)

 2CaCO 3  + 2H 2O Ca(HCO 3 ) 2 + Ca(OH) 2   2CaCO 3  + Mg(OH) 2 + 2H 2O Mg(HCO 3 ) 2 + 2Ca(OH) 2  27. Heavy water is (1) De-mineralised water (2) De-ionized water (3) Ordinary water containing dissolved salts of heavy metals (4) The compound of heavier isotope of hydrogen with oxygen (D2O) Sol. Answer (4) The compound of heavier isotope of hydrogen with oxygen (D2O). Heavy water is chemically deuterium oxide (D2O). Deuterium is an isotope of hydrogen. 28. The structure of H2O2 is (1) Open book like

(2)

Closed book like

(3)

Pyramidal

(4)

Linear

Sol. Answer (1) H

95.0 pm 147.5 pm 111.5° O O 94.8°

H 98.8 pm 145.8 pm 90.2° O O 101.9°

H Gas phase

H Solid phase



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Hydrogen


29. The dihedral angle of H2O2 in solid phase is (1) 111.5°

(2)

90.2°

(3)

94.8°

(4)

101.9°

390.0 mL

(4)

112.5 mL

(4)

All of these

Sol. Answer (2) The dihedral angle of H2O2 in solid phase is 90.2°. 30. The volume of O2 liberated from 0.96 g of H 2O2 at STP is (1) 224.6 mL

(2)

316.2 mL

(3)

Sol. Answer (2)

 2H 2O + O 2 2H 2O 2  2  34g

22.4 L

= 68 g 22.4 L of O2 at NTP obtained from H2O2 = 68 g 0.96 g of H2O2 =

22. 4  10

3

68

 0.96

= 0.33  10 3  0.96 = 0.3168  103 = 316.8 mL SECTION - B

Objective Type Questions 1.

H2O2 acts as (1) Oxidising agent

(2)

Reducing agent

(3)

Bleaching agent

Sol. Answer (4) H2O2  H 2O + [O] Due to nascent oxygen, it can act as a permanent bleaching agent H 2O 2 + H 2O 2 +1

–1

+1

 

–1

2H 2O + O 2 +1

–2

0

Oxidation state of hydrogen remains the same. Oxygen in one molecule of H2O2 is oxidised to O2 (–1  0) whereas in another molecule is reduced to H2O (–1  –2). Thus, H2O2 acts both as an oxidizing and reducing agent. 2.

Hydrogen can be prepared by (1) Electrolysis of acidified water

(2)

Bosch's process

(3) Lane's process

(4)

All of these

Sol. Answer (4) Hydrogen can be produced by all the methods i.e. electrolysis of acidified water, Bosch's process and Lane's process. 3.

Commercial hydrogen is obtained from (1) Coal gas

(2)

Water gas


(3)

Air

(4)

Producer gas



Hydrogen

53

Sol. Answer (2) 1270 K  CO + H 2 C + H 2O(g)  Ni

 nCO(g) + (2n+1)H 2 (g) C nH 2n+2 + nH 2O(g)  Ni 1270 K

Water gas  CO + H2. 4.

Which is a source of nascent hydrogen? I.

Zn + dil HCl

II.

CH3OH + Na

III. Electrolysis of H2O

IV.

Silent electric discharge of H2O2

(1) I & II

(2)

II & III

(3)

I, II, III

(4)

IV

(3)

H2O2

(4)

H2

(3)

H2O2

(4)

D2O

Sol. Answer (1) Zn + 2HCl  ZnCl2 + 2[H] Nascent hydrogen Na/CH3OH is another form of producing nascent hydrogen. 5.

Electrolysis of 50% H2SO4 gives (1) H2O

(2)

D2O

Sol. Answer (3) H 2S 2 O 8 + H 2 O



H2 SO 4 +



H 2 SO 5 Peroxomono sulphuric acid



H2SO5 + H 2O  H 2SO4 + H 2O2. 6.

Lane's process is for the preparation of (1) H2

(2)

H2O

Sol. Answer (1) By Lane's process hydrogen is formed when super-heated steam is passed over iron and heated to about 1023 – 1073 K 3Fe + 4H 2 O Steam

7.

 1023–1073 K

Fe 3O 4 + 4H 2

.

In water gas shift reaction reactant is (1) H2 + H 2O

(2)

H2 + CO 2

(3) H2 + CO + H 2O(g)

(4)

H2 + D 2

Sol. Answer (3) 673 K  CO 2 (g) + H 2 (g) CO(g) + H 2O  g  FeCrO 4

Water-gas shift reaction, water gas C + H 2O  CO + H2. Aakash Educational Services Pvt. Ltd.


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8.

Hydrogen


In Ortho and Para hydrogen, the nuclear spin respectively are (1) Parallel and opposite

(2)

Opposite and parallel

(3) It may be parallel or opposite

(4)

They do not differ in nuclear spin

Sol. Answer (1) Ortho and para forms have one and zero nuclear spin respectively

Ortho-hydrogen (parallel nuclear spin) 9.

Para-hydrogen (Anti-parallel nuclear spin)

When hydrolith is treated with water it yields (1) H2

(2)

H2O2

(3)

NaH

(4)

N2

(3)

d -block metals

(4)

All of these

Sol. Answer (1) Hydrolith is the trade name for impure (90%) CaH2 CaH2 + 2H2O  Ca(OH)2 + 2H2 10. Interstitial hydrides are formed by (1) s-block metals

(2)

p-block metals

Sol. Answer (3) Metallic or interstitial hydrides are formed when hydrogen reacts with transition metals. 11.

The group of elements responsible for hydride gap (1) Mn, Ca, Ni

(2)

Mn, Fe, Li

(3)

Mn, Fe, Co

(4)

Mn, Cu, Cl

Sol. Answer (3) The metals of 7, 8 and 9 groups do not form hydrides and hence this region of periodic table is known as hydride gap. 12. Which of the following is interstitial hydride? (1) CaH2

(2)

CuH

(3)

PH3

(4)

NaH

Molecular hydrides (4)

H2O

Sol. Answer (2) Interstitial hydrides are formed by transition elements. 13. Hydrogen exists in atomic state in which of the following compounds? (1) Metallic hydrides

(2)

Ionic hydride

(3)

Sol. Answer (1) Metallic or interstitial hydrides have hydrogen atoms occupied interstitial positions in the metal lattices. This is due to the small size of hydrogen atoms compared to the metal ions. In these hydrides, hydrogen exists in atomic rather than ionic form. 14. The velocity of neutrons in nuclear reactor is slowed down by (1) Heavy water

(2)

Ordinary water

(3)

Zinc rod

(4)

Fused caustic soda

Sol. Answer (1) Water that contains deuterium atoms in place of hydrogen atoms; used as a moderator for reactor cores. Aakash Educational Services Pvt. Ltd.



Hydrogen

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15. Heavy water has maximum density at (1) 4°C

(2)

11.6°C

(3)

0°C

(4)

273 K

(1) H2O

(2)

D2O

(3) Water at 4°C

(4)

Water obtained by repeated distillation

Sol. Answer (2) Heavy water has maximum density at 11.6°C. 16. Heavy water is

Sol. Answer (2) Heavy water is chemically deuterium oxide (D2O). 17. Which of the following will determine whether the given colourless liquid is water or not? (1) Melting

(2)

Tasting

(3) Phenolphthalein

(4)

Adding a pinch of anhydrous CuSO4

Sol. Answer (4) On addition of CuSO4 (white in colour) into a beaker containing a colourless liquid, water will turn into a blue solution. This is because CuSO4 will combine with H2O to form a blue compound CuSO45H2O. 18. Select the correct statement. (1) O–H bond is stronger than O–D bond (2) O–H bond is weaker than O–D bond (3) Permanent hardness of water is due to the presence of bicarbonates of calcium and magnesium (4) O–H and O–D bond strength is same Sol. Answer (2) O–H bond is weaker than O–D bond because dipole-dipole forces. 19. Heavy water is called as heavy because it is (1) A heavy liquid

(2)

An oxide of heavier isotope of oxygen

(3) An oxide of deuterium

(4)

Less denser than H2O

Sol. Answer (3) Heavy water is chemically deuterium oxide (D2O). Hence, it is called heavy water. 20. Structure of blue vitriol shows presence of (1) Coordinate bond

(2) Covalent bond

(3)

Hydrogen bond

(4)

All of these

Sol. Answer (4)

H

H

H

O

O Cu

H

H

H

O

–

O

O

O

H

H

H

O S

H

O

–

O

The structure shows presence of coordinate bond, covalent bond and hydrogen bond. Aakash Educational Services Pvt. Ltd.


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Hydrogen


21. Both cation and anion impurities can be removed from hard water by using (1) Zeolites

(2)

Organic ion exchanges

(3) Calgon

(4)

All of these

Sol. Answer (2) Synthetic resins method is superior to zeolite method because they remove all types of unwanted cations as well as anions present in water. 22. Which of the following is correct? (1) LiH is thermally more stable than CsH (2) Density of H2 is about

1 14

th of that of air

(3) Atomic hydrogen is much more reactive than ordinary hydrogen (4) All of these Sol. Answer (4) Small size of Li+ ion which is capable for polarizing 1 14

th that

H

ion make LiH most stable. Density of H 2 is about

of air. Atomic hydrogen is more reactive than ordinary hydrogen.

23. When same amount of zinc is treated separately with excess of sulphuric acid and excess of sodium hydroxide solution, the ratio of volumes of hydrogen evolved is (1) 1 : 1

(2)

1:2

(3)

2:1

(4)

9:4

(4)

CCl4

Sol. Answer (1) Zn + H2SO4  ZnSO4 + H 2 Zn + 2NaOH  Na2ZnO2 + H 2 The ratio of volumes of H2 evolved in both the cases is 1 : 1. 24.

CH3D  Cl 2

h Product. The product is  (1 mole)

(1) CH2DCl

(2) CH3Cl

(3)

CDCl3

Sol. Answer (1) CH 3D + Cl 2

  h

1 mole

CH 2DCl + HCl

D is a heavier atom, hydrogen will be more replacable with energy just of 1 mole h the above product is only possible. 25. Hydrogen peroxide is used as (1) Oxidising agent only

(2)

Reducing agent only

(3) Both as oxidising and reducing agent

(4)

Drying agent

Sol. Answer (3) The oxidising nature of H2O2 is due to the possession of labile oxygen atom H2O2  H2O + (O) It acts as a reducing agent in both acidic and alkaline medium towards powerful oxidising agents H2O2  2H+ + O 2 + 2e –

(in acidic medium)

H2O2 + 2OH–  2H2O + O 2 + 2e–

(in alkaline medium)




Hydrogen

57

26. H2O2 is manufactured these days (1) By the action of H2O2 on BaO

(2)

By the action of H2SO4 on Na2O

(3) By electrolysis of 50% H2SO4

(4)

By burning hydrogen in excess of oxygen

(3)

D2

Sol. Answer (3) 2H2SO4  2H+ + 2HSO4– Cathode : 2H+ + 2e –  H 2 Anode : 2HSO4–  H 2S2O8 +

2e

27. Which of the following is most reactive? (1) H2

(2)

H (nascent)

(4)

H (atomic)

Sol. Answer (4) The reactivity order of hydrogen is, H2 < Nascent hydrogen < Atomic hydrogen. 28. H2O2 restores the colour of old lead paintings, blackened by the action of H2S gas by (1) Converting PbO2 to Pb

(2)

Oxidising PbS to PbSO4

(3) Converting PbCO3 to Pb

(4)

Oxidising PbSO3 to PbSO4

Sol. Answer (2) PbS(s) + 4H 2O2(aq)  PbSO4(s) + 4H2O(l) 29. In the reaction 2K3[Fe(CN)6] + 2KOH + H2O2  2K4[Fe(CN)6] + 2H2O + O2 , H2O2 acts as (1) Reducing agent

(2)

Oxidising agent

(3)

Knocking agent

(4)

Bleaching agent

Sol. Answer (1) H2O2 reduces potassium ferricyanide to potassium ferrocyanide 2K3[Fe(CN)6] + 2KOH + H2O2  2K4[Fe(CN)6] + 2H2O + O2. 30. Decomposition of H2O2 can be slowed down by addition of small amount phosphoric acid which act as (1) Stopper

(2)

Inhibitor

(3)

Detainer

(4)

Promotor

Sol. Answer (2) In a reaction inhibitor is a substance that decreases the rate of a chemical reaction. Thus, phosphoric acid is an inhibitor. 31. When 50% solution of H2SO4 is electrolysed by passing a current of high density at low temperature then main products of electrolysis are (1) Oxygen and Hydrogen

(2)

H2 and peroxy disulphuric acid

(3) H2 and SO2

(4)

O2 and peroxy disulphuric acid

Sol. Answer (2) 2H2SO4  2H+ + 2HSO4– 2H+ + 2e –  H2 2HSO4–  H 2S2O8 +

2e

Peroxy disulphuric acid Aakash Educational Services Pvt. Ltd.


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Hydrogen


32. H2O2  H2O + O2. This represents (1) Oxidation of H2O2

(2)

Reduction of H2O2

(3) Disproportionation of oxygen

(4)

Acidic nature of H2O2

(1) 1 ml of H2O2 solution gives 20 L of O2 at NTP

(2)

1 mole of H2O2 give 20 ml of O 2 at NTP

(3) 1 g of H2O2 give 20 ml of O2 at NTP

(4)

1 ml of H2O2 solution give 20 ml of O2 at NTP

Sol. Answer (3) –1 x 2

+1 x 2

H2O2

–2

H2O

0

+ O2

Red Oxid

33. 20 volume hydrogen peroxide means

Sol. Answer (4) This tells how much oxygen is released from 1 ml of hydrogen peroxide solution. 1 ml of 10 volume gives 10 ml oxygen. 1 ml of 20 volume gives 20 ml oxygen. 34. 1 ml of H2O2 solution gives 10 ml of O2 at N.T.P. It is (1) 10 vol H2O2

(2)

20 vol H2O2

(3)

30 vol H2O2

(4)

40 H2O2

(3)

1.7

(4)

5.1

(4)

8.0

Sol. Answer (1) 1 ml of 10 volume H2O2 gives 10 ml oxygen at NTP 35. The normality of 10 volume H2O2 is nearly (1) 2.1

(2)

3.4

Sol. Answer (3) ∵

Volume strength = Normality × 5.6

Normality of 10 volume H2O2 solution 

10 5.6

 1.78 N

36. The amount of H2O2 present in 1 L of 1.5 N H2O2 solution is (1) 2.5 g

(2)

25.5 g

(3)

3.0

Sol. Answer (2) 1.5 N means 1.5 gram equivalent in 1 L solution Normality 



1.5



Weight eq. wt of H 2O 2  Volume of solution (in litre)

wt 17

wt = 1.5  17 = 25.5 g 37. H2O and H2O2 resemble in (1) Hybridisation of oxygen

(2)

Oxidation state of oxygen

(3) Structure

(4)

Bond angle

Sol. Answer (1) Hybridisation of oxygen in H2O and H2O2 is sp3. Aakash Educational Services Pvt. Ltd.



Hydrogen

59

38. Boiling point of D2O is (1) 100°C

(2) 105.5°C

(3)

101.4°C

(4)

102.6°C

Sol. Answer (3) +

–

+

–

It turns out that O D O "H-Bonding" is slightly stronger than O H O bond. The slightly greater H-bonding strength increases the intermolecular forces in D2O compared to H2O and D2O has a higher boiling point (by 1.5ºC) than H2O. SECTION - C

Previous Years Questions 1.

Which of the following statements about hydrogen is incorrect?

[NEET-2016]

(1) Dihydrogen does not act as a reducing agent (2) Hydrogen has three isotopes of which tritium is the most common (3) Hydrogen never acts as cation in ionic salts (4) Hydronium ion, H3O+ exists freely in solution Sol. Answer (1 & 2) Fact. 2.

In acidic medium, H2O2 changes Cr2O72 to CrO5 which has two (–O–O–) bonds. Oxidation state of Cr in CrO5 is [AIPMT-2014] (1) +5

(2)

+3

(3)

+6

(4)

–10

Sol. Answer (3) O

O +6

O

Cr O

3.

O

The ease of adsorption of the hydrates alkali metal ions on an ion-exchange resins follows the order [AIPMT (Prelims)-2012] (1) K+ < Na +< Rb+ < Li +

(2)

Na+ < Li + < K + < Rb +

(3) Li+ < K + < Na+ < Rb+

(4)

Rb+ < K + < Na+ < Li +

Sol. Answer (3) Smaller the ion more is the extent of hydration. The hydration enthalpies of alkali metal ions decrease with increase in ionic size. Hydration enthalpy is proportional to nuclear charge. Li+ > Na+ > K+ > Rb+ > Cs+ More the hydrated ion larger will be its size. In contrast, when the aqueous ions are adsorbed on an ionexchange resin, the order of the strength of adsorption is hydrated, the size of the hydrated 4.

Li

Li < Na < K < Rb

. As

Li

ion is most highly

ions is maximum.

Some statements about heavy water are given below a. Heavy water is used as a moderator in nuclear reactors b. Heavy water is more associated than ordinary water c.

Heavy water is more effective solvent than ordinary water

Which of the above statements are correct ? (1) a and b

(2)

a, b and c


[AIPMT (Mains)-2010] (3)

b and c

(4)

a and c


60

Hydrogen


Sol. Answer (1) Heavy water is used as a moderator in nuclear reactors. Heavy water is more associated than ordinary water. 5.

Hydrogen is prepared from H2O by adding (1) Ca, which acts as reducing agent

(2)

Al, which acts as oxidising agent

(3) Ag, which acts as reducing agent

(4)

Au, which acts as oxidising agent

Sol. Answer (1) Ca + 2H2O  H 2 + Ca(OH)2 6.

The hydride ion H– is stronger base than its hydroxide ion OH–. Which of the following reaction will occur if sodium hydride (NaH) is dissolved in water? (1) H– + H 2O  No reaction

(2)

H– (aq) + H2O  H 2O

(3) H– (aq) + H2O(l)  OH– + H 2

(4)

None of these

Sol. Answer (3) NaH + H2O  NaOH + H2 7.

Which of the following statements about the interstitial compounds is incorrect? (1) They are chemically reactive (2) They are much harder than the pure metal (3) They have higher melting points than the pure metal (4) They retain metallic conductivity

Sol. Answer (1) Interstitial compounds are generally not chemically reactive. 8.

The volume strength of 1.5 NH2O2 solution is (1) 8.8

(2)

8.4

(3)

4.8

(4)

5.2

Sol. Answer (2) Molarity 

2  Volume strength 22.4

1.5 N = 0.75 M H2O2

 0.75  9.

2  Volume strength 22.4

 Volume strength = 0.75  11.2 = 8.4

Which one of the following pairs of substances on reaction will not evolve H2 gas? (1) Copper and HCl (aqueous)

(2)

Iron and steam

(3) Iron and H2SO4 (aqueous)

(4)

Sodium and ethyl alcohol

Sol. Answer (1) Copper being weakly electropositive, is not very reactive. It resists the action of most of the common chemical reagents like air, H2O, acids and alkalies. Non-oxidising acids like HCl and dilute H2SO4 have no effect on copper in absence of air/O2. Aakash Educational Services Pvt. Ltd.



Hydrogen

61

10. Zn gives H2 gas with H2SO4 and HCl but not with HNO 3 because (1) Zn act as oxidizing agent when react with HNO3 (2) HNO3 is weaker acid than H2SO4 and HCl (3) In electrochemical series Zn is above hydrogen (4)

NO3

is reduced in preference to hydronium ion

Sol. Answer (4) 4Zn + 10HNO3  4Zn(NO3)2 + NH4NO3 + 3H2O 11.

Which pair of substances gives same gaseous product, when these react with water? (1) K and KO2

(2)

Ba and BaO2

(3)

Ca and CaH2

(4)

Na and Na2O2

(3)

Nuclear charge

(4)

Nuclear reaction

Sol. Answer (3) Ca + 2H2O  Ca(OH)2 + H 2 CaH2 + 2H2O  Ca(OH)2 + 2H2 12. Ortho and para hydrogen differ in (1) Proton spin

(2)

Electron spin

Sol. Answer (1) If the spins of the nuclei of two H-atoms of H 2 molecule are in the same direction, the dihydrogen is called ortho hydrogen. But if the spins of the nuclei of two hydrogen atoms are in opposite directions, it is called para hydrogen. 13. Action of water or dilute mineral acids on metals can give (1) Monohydrogen

(2)

Tritium

(3)

Dihydrogen

(4)

Trihydrogen

Sol. Answer (3) 2Na + HCl(dil.)  NaCl + H2 14. Deuterium resembles hydrogen in chemical properties but reacts (1) More vigorously than hydrogen

(2)

Faster than hydrogen

(3) Slower than hydrogen

(4)

Just as hydrogen

Sol. Answer (3) Deuterium resembles hydrogen in chemical properties and gives all characteristic reactions of hydrogen, forming analogous compounds. It, however reacts more slowly and less completely than hydrogen. 15. Spin isomerism is shown by (1) Dichloro benzene

(2)

Hydrogen

(3)

Dibasic acid

(4)

n-butane

Sol. Answer (2) Spin isomerism is shown by hydrogen i.e. ortho and para hydrogen. 16. Hydrogen can be fused to form helium at (1) High temperature and high pressure

(2)

High temperature and low pressure

(3) Low temperature and high pressure

(4)

Low temperature and low pressure

Sol. Answer (1) High temperature and high pressure favour the fuse of hydrogen to form helium. For example, on the sun's atmosphere nuclear fusion reactions keep occurring as hydrogen gets fused to form helium. Aakash Educational Services Pvt. Ltd.


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Hydrogen


17. What is formed when calcium carbide reacts with heavy water (1) C2D2

(2)

CaD2

(3)

Ca2D2O

(4)

CD2

(3)

3

(4)

4

Sol. Answer (1) CaC2 + D 2O  Ca(OD)2 + D–CC–D 18. Maximum number of hydrogen bonding in H2O is (1) 1

(2)

2

Sol. Answer (4) The two hydrogens of the water molecule can form hydrogen bonds with other oxygen-like in ice, and the two lone pair of electrons. An oxygen of the water molecule can attract other hydrogens in ice. Hence four possible hydrogen bonds. 19. In which of the following reaction hydrogen peroxide is a reducing agent? (1) 2FeCl2 + 2HCl + H2O2  2FeCl3 + 2H 2O

(2)

Cl2 + H2O2  2HCl + O2

(3) 2HI + H2O2  2H2O + I 2

(4)

H2SO3 + H 2O2  H 2SO4 + H2O

Sol. Answer (2) Cl2 + H 2O2  2HCl + O2 (alkaline medium) Here H2O2 is a reducing agent. 20. There is a sample of 10 volume of hydrogen peroxide solution. Calculate its strength. (1) 3.00%

(2)

4.045%

(3)

2.509%

(4)

3.035%

Sol. Answer (4) 10 volume H2O2 implies the 1 L of H2O2 gives 10 L of O2 at S.T.P.

 H 2O(l) + 2H 2O 2 (l)  2 34 g

O 2 (g) 22.4 L at STP

22.4 L of O2 at STP is given by H2O2 = 68g 10 L of O2 at STP is given by H 2O2



68  10  30.36 g 22.4

 Strength of H2O2 = 30.36 gL–1  1000 ml = 30.36 g  100 ml =

30.36 1000

 100

= 3.036 g i.e., 3.036 %

21. In lab H2O2 is prepared by (1) Cold H2SO4 + BaO2

(2)

HCl + BaO2

(3) Conc. H2SO4 + Na 2O2

(4)

H2 + O2

Sol. Answer (1) BaO28H2O + H 2SO4  BaSO4 + H 2O2 + 8H 2O Aakash Educational Services Pvt. Ltd.



Hydrogen

63

22. H2O2 acts as an oxidising agent in (1) Acidic medium only

(2)

Alkaline medium only

(3) Neutral medium only

(4)

Acidic and alkaline medium

Sol. Answer (4) Acidic medium : PbS + 4H2O2  PbSO4 + 4H2O Alkaline medium : MnSO4 + H 2O2 + 2NaOH  MnO2 + Na2SO4 + 2H2O 23. Hydrogen peroxide is reduced by (1) Ozone

(2)

Barium peroxide

(3) Acidic solution of KMnO4

(4)

Lead sulphide suspension

Sol. Answer (4) PbS + 4H 2O2  PbSO4 + 4H2O 24. The volume of oxygen liberated from 15 ml of 20 volume H2O2 is (1) 250 ml

(2)

300 ml

(3)

150 ml

(4)

200 ml

(3)

56 ml

(4)

336 ml

(4)

10%

Sol. Answer (2) 20 volume of H2O2 gives 20 ml of oxygen at STP

 15 ml of 20 volume H2O2 will yield 15  20 = 300 ml of oxygen 25. The volume of oxygen liberated from 0.68 g of H2O2 is (1) 112 ml

(2)

224 ml

Sol. Answer (2) 2H 2O 2



234 g

2H 2O +

O2 22400 ml

Now 2 × 34 = 68 g of H 2O2 liberates 22400 ml O2 at STP.

 0.68 g of H2O2 liberate 

0.68  22400 68

 224 mL of O

2

at STP

26. 20 volume H2O2 solution has a strength of about (1) 30%

(2)

6%

(3)

3%

Sol. Answer (2) 20 volume solution of H2O2 means that 1 L of this H2O2. solution will give 20 L of oxygen at STP 2H 2O 2   2H 2O + O 2 2  34

22.7 L at STP

= 68 g Aakash Educational Services Pvt. Ltd.


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Hydrogen


22.7 L of O2 at STP is obtained from H 2O2 = 68 g

 20 L of O2 at STP is obtained from H 2O2 

68 +20  59.91 g/L = 6% H2O2 22.7

27. The H – O – O bond angle in H2O2 (g) is (1) 107.28°

(2)

109.28°

(3)

104.5°

(4)

94.8°

Sol. Answer (4) According to the structure. It is 94.8°. SECTION - D

Assertion-Reason Type Questions 1.

A : ScH2 is an example of ionic hydride. R : All metal forms ionic hydride.

Sol. Answer (4) ScH2 is an example of metallic hydride metals form covalent hydride also. 2.

A : Temporary hardness is due to

–

HCO3

ions.

R : Permanent hardness is due to CaCl2. Sol. Answer (2) Temporary hardness is due to the presence of bicarbonates of calcium and magnesium. Permanent hardness is due to the presence of chlorides and sulphides of calcium and magnesium dissolves in water. 3.

A : The molarity of 20 volume H2O2 is 3.58 M. R : Volume strength = 5.6 × M.

Sol. Answer (4) The normality of 20 volume H2O2 is 3.58 N Volume strength = 5.6  N 4.

A : Permanent hardness of water is due to the presence of chlorides or sulphates of Ca or Mg. R : Permanent hardness is removed by boiling.

Sol. Answer (3) Temporary hardness can be removed by boiling. 5.

A : Atomic hydrogen is more reactive than nascent hydrogen. R : The energy content of atomic hydrogen is more than nascent hydrogen.

Sol. Answer (1) The reactivity order of hydrogens is, H2 < Nascent hydrogen < Atomic hydrogen. 6.

A : The O – O bond length in H2O2 is shorter than that of O2F2. R : H2O2 is an ionic compound.

Sol. Answer (4) Due to high electronegativity of Fluorine and smaller size, the O–O bond length in H2O2 is larger than that of O2F2. Aakash Educational Services Pvt. Ltd.



7.

Hydrogen

65

A : H2O2 reacts with K2Cr 2O7 to give blue colour. R : H2O2 can act as reducing agent.

Sol. Answer (2) K2Cr 2O7 + H 2SO4 + 4H 2O2  2CrO5 + K 2SO4 + 5H 2O H2O2 can act as reducing agent. 8.

A : Water is a poor solvent for non-polar compounds. R : Covalent compounds interact weakly that even van der Waal forces cannot be broken.

Sol. Answer (1) Water is a polar solvent. Covalent compounds interact weakly that even van der Waal's forces cannot be broken. 9.

A : Zn dissolve in excess of NaOH solution so as to give H2. R : Zn(OH)2 is neutral in nature.

Sol. Answer (3) Zn(OH) 2 is amphoteric in nature. 10. A : Complete hydrolysis of one mole of peroxydi -sulphuric acid gives one mole of H2 O 2 an d 2 mole of H2SO4. R : Peroxydisulphuric acid has zero peroxy linkage. Sol. Answer (3) Peroxydisulphuric acid has peroxy linkages. 11. A : H2O2 liberate O2 on reaction with KMnO4 in acidic medium. R : KMnO4 oxidises H2O2 to O2. Sol. Answer (1) 2MnO4– + 6H + + 5H 2O2  2Mn2+ + 8H 2O + 5O2 12. A : H2 is liberated by action of aluminium with conc. NaOH. R : Aluminium on reaction with NaOH forms sodium meta-aluminate. Sol. Answer (2) 2Al + 2NaOH



2NaAlO 2 + H 2



Sodium meta aluminate



13. A : pH of water is temperature dependent. R : Boiling water has pH less than 7. Sol. Answer (2) pH of water is dependant on temperature. Boiling of water has pH less than 7. 14. A : H2O2 decomposes on exposure to light. R : It is stored in dark waxlined plastic vessel. Sol. Answer (2) H2O2 decomposes on exposure to light which is why it is stored in dark wax lined plastic vessel.



66

Hydrogen


15. A : Dihedral angle of H2O2 in gas phase is greater than in solid phase. R : H2O2 has planar structure. Sol. Answer (3) Dihedral angle in gas phase = 111.5° solid phase = 90.2° Hydrogen peroxide is non-linear, non-planar molecule.









CLS Aipmt 17 18 XI Che Study Package 3 SET 2 Chapter 9

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