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1051.

Explain the process of softening of temporary hardness by Clark’s method.

Answer»

Temporary hard water is converted into soft water by adding required amount of calcium hydroxide. In this method Mg2+ ions are precipitated as Mg(OH)2 and Ca2+ ions are precipitated as CaCO3.

Mg (HCO3)2 →Mg (OH)2 + 2CO2

Ca (HCO3)2→ 2CaCO→ 2H2O + 2CO2.

The insoluble precipitates can be removed by filtration.

1052.

Name the alkali metal which shows diagonal relationship with Mg?

Answer» Li.............
1053.

Give four uses of hydrogen peroxide.

Answer»

(i) It is used as oxidizing agent and reducing agent. 

(ii) Its dilute solution is used as mild antiseptic. 

(iii) It is used as bleaching agent. 

(iv) Cone. H2O2 is used as rocket fuel.

1054.

What is the difference between hydrolysis and hydration?

Answer»

Hydrolysis is the reaction of salt and water to form acidic or basic solution.

AcONa + H2​O→ AcOH + NaOH

Hydration is the addition of water to ions or molecules.

CuSO4 ​+ 5H2​O→ CuSO4​.5H2​O

1055.

What is the importance of heavy water?

Answer»

Heavy water is an important compound due to following reasons : (i) It is employed in nuclear reactors as a moderator as it slows down the fast moving neutrons. (ii) It is widely used as a tracer compound for studying the mechanism of many reactions. (iii) It can be used for production of deuterium and deutero-compounds. 

1056.

Describe the following in brief a)Hydrogen economy b) Fuel cell c) Uses of Hydrogen peroxide

Answer»

a) The storage and transportation of liquid hydrogen as a fuel is hydrogen economy 

b) Those cells in which the energy of combustion is converted into electricity are called fuel cells eg-H2-O2 fuel cell 

c) In bleaching, as antiseptic, an oxidizing and reducing agent.

1057.

What is the difference between hydrolysis and hydration?

Answer» Hydrolysis is defined as a chemical reaction in which hydrogen and hydroxide ions `(H^(+) and OH^(–) "ions")` of water molecule react with a compound to form products. For example:
Hydration is defined as the addition of one or more water molecules to ions or molecules to form hydrated compounds. For example:
1058.

Describe the Hydrogen economy (Hydrogen as fuel).

Answer»

The electricity cannot be stored to run automobiles. It is not possible to store and transport nuclear energy. Hydrogen is an alternative source of energy and hence called as 'hydrogen economy‘. Hydrogen has some advantages as fuel

  • Available in abundance in combined form as water. 
  • On combustion produces H2O. Hence pollution free. 
  • H2-O2 fuel cell give more power. 
  • Excellent reducing agent. Therefore can be used as substitute of carbon in reduction for processes in industry. 

Obstacles in hydrogen economy 

Transportation: 

  • Hydrogen gas is explosive and hence it is difficult to store and transport. Formation of hydrogen from H2O: 
  • The cheaper production of the hydrogen is basic requirement of hydrogen economy which is not possible now.
  • The main aim and advantage of hydrogen economy is to transmit energy in four of hydrogen.
1059.

Which one the following is a covalent hydride ?A. `CaH_(2)`B. NaHC. `BH_(3)`D. `BeH_(2)`

Answer» Correct Answer - C
Hydrides are binary ompounds of hydrogen.
These can be calssified into four groups :
(i) lonic hydrides :` NaH, CaH_(2), LiH`
(ii) Covalent hydrides : `B_(2)H_(6), NH _(3), SBH_(3)`
(iii) Polynucles hydrides : `LiAIH_(4), NaBh_(4)`
(iv) Intersitital hydrical are those in which hydrogen is trapped in the interetitial space of transition of transition metals .
1060.

Only one element of …….from hydride.A. Groups 6B. Group7C. Group 8D. Group 9

Answer» (a) Only chromium (Cr) of group 6 elements forms CrH.
1061.

Only one element of …….from hydride.A. group 6B. group 7C. group 8D. group 9

Answer» Correct Answer - A
Only one element of group 6,.i.e Cr forms hydrides .
Note Metiallic (or interstitial ) hydridedes are fromed by many d-block and f-block elements. However, the metals of group 7,8 and 9 do not from hydride. Even from group 6, only chromium form CrH. These hydrides conduct heat and electricity though not as efficiently as their parent metals do.
1062.

What do you mean by hydrogen economy?

Answer»

Use of Hydrogen as a fuel due to the Hydrogen releases large quantity of heat on combustions.

1063.

The element whose hydride contains maximum number of hydrogen per atom of the element isA. NaB. OC. BD. Si.

Answer» Correct Answer - D
Hydride of `Si(SiH_(4))` contains more hydrogen atoms than hydrides of Na(NaH), `O(H_(2)O), B(BH_(3))`
1064.

Indicator type silica gel used as a dehumidifier containsA. `Cu^(2+)ions`B. `Ni^(2+)ions`C. `Co^(2+)ions`D. `Fe^(2+)ions`.

Answer» Correct Answer - C
Indicator type of silica gel used as a dehumidifier contains `Co^(2+)` ions, when dry it is blue in colour and on absorbine moisture it becomes pink.
1065.

How does calcium carbide react with heavy water.

Answer»

CaC2 + 2 D2O = Ca(OD)2 + C2D2

1066.

What is formed when calcium carbide reacts with heavy water?A. `C_(2)D_(2)`B. `CaD_(2)`C. `Ca_(2)D_(2)O`D. `CD_(2)`.

Answer» Correct Answer - A
`CaC_(2)+2D_(2)OtoC_(2)D_(2)+Ca(OD)_(2)`.
1067.

Which isotope of hydrogen contains equal number of proteons and neutrons?

Answer» Deuterium `(._(1)^(2)D)`. It has one proton and one neutron.
1068.

The sum of the number of neutrons and proton in the isotope of hydrogen isA. 6B. 5C. 4D. 3 .

Answer» Correct Answer - D
The sum of number of neutrons (2) and proton (1) in tritium is 3.
1069.

Hydrogen can be obtained from water, by the action of water onA. Calcium carbideB. Calcium hydrideC. Calcium oxideD. Calcium

Answer» Correct Answer - B
`Ca+H_(2)O to Ca (OH)_(2) + H_(2)`
1070.

The oxide that gives `H_(2)O_(2)` on treatment with dilute `H_(2)S0_(4)` isA. `PbO_(2)`B. `BaO_(2).8H_(2)O + O_(2)`C. `MnO_(2)`D. `TiO_(2)`

Answer» Correct Answer - B
Oxides such as `BaO_(2), Na_(2)O_(2)` etc, which contain peroxides (i.e., `-O-O or O_(2)^(2-)`) on treatment with dilute `H_(2)SO_(4)` give `H_(2)O_(2)` but dioxides (O= M= O, where M is the metal atom) such as `PbO_(2), MnO_(2), TiO_(2)` do not gives `H_(2)O_(2)` on treatment with dilute `H_(2)SO_(4)`
`underset("peroxide")underset("Hydrated barium")(BaO_(2). 8H_(2)O(S) + H_(2)SO_(4)(aq)) to BaSO_(4)(S)+ underset("peroxide")underset("Hydrogen")(H_(2)O_(2)(aq)+ 8H_(2)O(l))`
1071.

The oxide that gives `H_(2)O_(2)` on treatment with a dilute acid isA. `PbO_(2)`B. `Na_(2)O_(2)`C. `MnO_(2)`D. `TiO_(2)`.

Answer» Correct Answer - B
`Na_(2)O_(2)+H_(2)SO_(4)toNa_(2)SO_(4)+H_(2)O_(2)`
1072.

Hydrogen burns in oxygen to form1. hydrogen sulphide2. nitrates3. water4. ammonia

Answer»

Hydrogen burns in oxygen to form water.

1073.

Nitrates of all metals areA. Soluble in waterB. InsolubleC. ColouredD. Unstable

Answer» Correct Answer - A
Lattice energy of all metal nitrate are less than that of their solvation energy so nitrates of metals soluble in water.
1074.

Hydrogen peroxide is a powerful oxidising agent, both in the acidic and alkaline medium. In acidic medium: `H_(2)O_(2)+2H^(o+)+2e^(ɵ)to2H_(2)O` In alkaline medium: `H_(2)O_(2)+2e^(ɵ)to2overset(Theta)(O)H` Hydrogen peroxide acts as a reducing agent towards powerful oxidising agents. In acidic medium: `H_(2)O_(2)to2H^(o+)+O_(2)+2e^(ɵ)` In alkaline medium, however, its reducing nature is more effective. `H_(2)O_(2)to2H^(o+)+O_(2)+2e^(ɵ)` In which of the following reactions, `H_2O_2` act as a reducing agent?A. `PbO_(2)+H_(2)O_(2)rarrPbO+H_(2)O+O_(2)`B. `Na_(2)SO_(3)+H_(2)O_(2)rarrNa_(2)SO_(4)+H_(2)O`C. `2KI+H_(2)O_(2)rarr2KOH+I_(2)`D. `KNO_(2)+H_(2)O_(2)rarrKNO_(3)+H_(2)O`

Answer» Correct Answer - A
`overset(+4)(PbO_(2)) + H_(2)O_(2) rarr overset(2+)PbO+H_(2)O + O_(2)`
1075.

Which of following could act as propelleant for rockets?A. Liquid oxygen+liquid argonB. Liquid nitrogen+liquid oxygenC. Liquid hydrogen+liquid oxgyenD. Liquid hydrogen+liquid nitrogen.

Answer» (c )is the correct answer.
1076.

What is true about ice ?A. Its density is more than waterB. It is a good conductor of heatC. It is a thermal insulatorD. Its density is less than water.

Answer» Correct Answer - C::D
Ice is a poor conductor of heat (a good thermal insulator) and its density is less than water.
1077.

Which of the following is/are hard water (s) ?A. Water containing some potash alumB. Water containing a few drops of HClC. Water containing common saltD. Water containing calcium nitrate.

Answer» Correct Answer - A::B::D
Water containning any cation other than `NH_(4)^(+)` and alkali metal is a hand water.
1078.

`H_(2)O_(2)` used in rockets has the concentrationA. `50%`B. `70%`C. `30%`D. `90%`

Answer» Correct Answer - A
`H_(2)O_(2)` is used as an oxidant for rocket fuel and has `90%` concentration to be used in rockets.
1079.

Deconposition of `H_(2)O_(2)` can be prevented by addition ofA. Ferrous sulphateB. oxalic acidC. OzoneD. Glycerol

Answer» Correct Answer - D
Decomposition of `H_(2)O_(2)` can be prevented by addition of because it can form H-bond with glycerol.
1080.

Decomposition of `H_(2)O_(2)` is prevented byA. NaOHB. `MnO_(2)`C. AcetanilideD. Oxalic acid.

Answer» Correct Answer - C
Decomposition of `H_(2)O_(2)` is prevented by acetanilide.
1081.

Answer the following: (a) Both conc. HCl and conc. `H_(2)SO_(4)` cannot be used to preapre hydrogen gas by reacting with zinc metal. (b) Pure zinc metal cannot be used for preparing hydrogen gas. (c ) Moist hydrogen connot be dried by passing through conc. `H_(2)SO_(4)`.

Answer» (a) Zinc metal reacts conc. HCl to evolve `H_(2)` gas. But as the acid is also highly voltile, it is vaporus get mixed with hydrogen vapours an as a result, thje gas will be contaminated and not pure.
Conc. `H_(2)SO_(4)` is a very strong oxidising agent. It oxdises hydrogen hydrogen envoled inthe reaction to form water. Along with that sulphur dioxide will be also evolved in the reaction.
`H_(2)SO_(4)("conc.")+Zn to ZnSO_(4)+H_(2)`
`H_(2)SO_(4) to H_(2)O+SO_(2)+O`
`H_(2)+O to H_(2)O`
`2H_(2)SO_(4)("conc.")+Zn to ZnSO_(4)+SO_(2)+2H_(2)O`
Therefore, conc `H_(2)SO_(4)` can be used to prepare hydrogen gas by reacting with zinc metal.
(b) When pure zinc metal is used for peparing hydrogen gas, a thin film of the gas is formed on the surface of hte metal and checks further and checks further action by the acid. In case the metal is impure, then a film of hydrogen does not stick on the metal surface and the metal surface and the metal completely reacts with the acid. Actually, small cells are produced by zinc and impurities present in it which accelerate the rate of reaction between the metal and the acid. Keeping this in mind, a small amount of `CuSO_(4)` is generally mixed with dilute `H_(2)SO_(4)` to act as impurity and to help in the formation of cells.
(c ) Hydrogen being a powerful reducing agent reduces conc.`H_(2)SO_(4)` (strong oxidising agent) to evolve of `SO_(2)` gas as follows:
`H_(2)SO_(4)+H_(2) to H_(2)O+SO_(2)`
Therefore, moist hydrogen cannot be dried by passing through conc. `H_(2)SO_(4)`.
1082.

`H_(2)O_(2)` on reacting with ethene givesA. EthaneB. EthanalC. Ethylene glycolD. Ethanol

Answer» Correct Answer - C
`{:(CH_(2),),(||,),(CH_(2),):}+H_(2)O_(2)to{:(CH_(2)OH,),(|,),(CH_(2)OH,):}`
1083.

Which is the correct statement?A. Hydrogen has the same IE as alkali metalsB. `H^(-)` ion has the same electronegativity as halogensC. `H^(-)` ion has oxidation number of -1D. `H^(-)` ion is not liberated at anode.

Answer» (c ) `H^(-)` ion has O.N=-1
1084.

The metal which gives hydrogen on reacting with acid as well as sodium hydroxide is:A. FeB. ZnC. CuD. none of thest

Answer» (b) `Zn+2HCl to ZnCl_(2)+H_(2) `
`Zn+2NaOH to N_(2)ZnO_(2)+H_(2)`
1085.

Assertion : `H_(2)O_(2)` react with PbS to form `PbSO_(4)`. Reason : `H_(2)O_(2)` is weak acidA. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.C. If Assertion is True but the Reason is False.D. If both Assertion & Reason are False.

Answer» Correct Answer - B
1086.

Assertion : Saline hydrides are non volatile, non conducting & crystalline solids. Reason : Saline hydrides are compounds of hydrogen with most of the p-block elements.A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.C. If Assertion is True but the Reason is False.D. If both Assertion & Reason are False.

Answer» Correct Answer - C
1087.

Assertion : Sulphur is oxidised by `H_(2)O_(2)` in presence of Fe(III) Reason :- Fe(III) oxidises sulphur to sulphateA. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.C. If Assertion is True but the Reason is False.D. If both Assertion & Reason are False.

Answer» Correct Answer - A
1088.

What is the oxidation state of oxygen of `H_2O_2` in the final products when it reacts with `As_2O_3`?

Answer» Correct Answer - -2
`H_(2)O_(2)+As_(2)O_(3)toAsO_(4)^(3-)+H_(2)O`
Oxidation number of `O` in `H_(2)O` is `-2`.
1089.

In which of the following hydrides, hydrogen exists in negative oxidation state?A. `HCl`B. `NaH`C. `CaH_(2)`D. `HI`

Answer» Correct Answer - B::C
`NaH` and `CaH_(2)` are ionic hydrides and `Na^(o+)` and `Ca^(2+)` lose electron which is gained by `H` to form `H^(ɵ)` ion.
1090.

What is the oxidation state of oxygen of `H_2O_2` in the final products when it reacts with `CIO_3`?

Answer» `H_(2)O_(2)+CrO_(3)^(ɵ)toCl_(2)O_(2)`
`2x=0`
1091.

In which of the following compound does hydrogen exhibit a negative oxidation state:A. `LiH`B. `H_(2)O`C. `HCl`D. none of these

Answer» Correct Answer - A
`LiH` is an ionic hydride, in which an electron is transferred from `Li` hence `Li^(o+)` and `H^(o+)` are formed.
1092.

What is the sum of protons, electrons and neutrons in the lightest isotope of hydrogen?

Answer» Correct Answer - 2
Protium or hydrogen (`._(1)^(1)H`) the highest isotope of hydrogen has `1` proton, `0` neutron andn `1` electron. Sum total of proton, neutron and electron is `2`.
1093.

What is the sum of protons, electrons and neutrons in the heaviest isotope of hydrogen?

Answer» Correct Answer - 4
Tritium `T` or `._(1)^(3)H` the heaviest isotope of hydrogen has `1` proton, `2` neutrons and `1` electrons. Hence sum total of proton, neutron and electron is `4`.
1094.

The number of neutrons in deuterium isA. `2`B. `3`C. `1`D. `0`

Answer» Correct Answer - C
Deuterium is `_(1)^(2)H`
Number of neutrons=Atomic mass-Atomic number
`=2-1=1`
1095.

In the reaction , `Ag_(2)O+ H_(2)O_(2) to 2Ag + H_(2)O+ O_(2)` `H_(2)O_(2)` acts asA. reducing agentB. oxidising agentC. bleaching agentD. none of these

Answer» Correct Answer - A
1096.

Why can dilute solutions of hydrogen peroxide not be concentrated by heating. How can a concentrated solution of hydrogen peroxide be obtained?

Answer»

H2O2 solution cannot be concentrated by heating beyond 30% solution as there is always possibility of explosions. The solution is concentrated at 35−40 Cunder reduced pressure of about 15 mm. Repeated distillation gives 90% H2O2. Further concentration is achieved by cooling with the help of solid COand ether bath till crystallisation sets in. Crystals are separated, melted and refrozen to get 99%  pureH2O2

1097.

Why can dilute solutions of hydrogen peroxide not be concentrated by heating? How can a conentrated solution of hydrogen peroxide be obtanied ?

Answer» A dilute solution of hydrogen peroxide is not conentrated upon heating because it decomposes at a temperature at a temperature below its boiling point.
`2H_(2)O_(2)(l) to 2H_(2)O(l)+O_(2)(g)`
Therefore, it has to be concentrated very carefully.
1098.

If -O-H bond is weadker than -O-D bond,A. The biological growth of a plant which is fed by `D_(2)O` is flastB. The biologicval growth of a plant which is fed by `H_(2)O` is fastC. The biological growth of a plant which fed both by `H_(2)O` or `D_(2)O` are sameD. Water does not have any role in plant growth.

Answer» Correct Answer - B
The bilological growth of a plant which is fed by `H_(2)O` is fast, if -O-H bond is weaker than -O-D bond.
1099.

Shape of `H_(2)O_(2)` molecule isA. non planarB. linearC. circularD. planar.

Answer» Correct Answer - A
`H_(2)O_(2)` molecule is nonplanar.
1100.

Oxidation state of oxygen in `H_(2)O_(2)` isA. `-2`B. `-1`C. 0D. `+2`.

Answer» Correct Answer - B
Oxidation number of oxygen in `H_(2)O_(2)` is -1.