Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

11.

Identify the wrong statement in the following.

  • Amongst isoelectronic species, smaller the positive charge on the cation, smaller is the ionic radius

  • Amongst isoelectronic species, greater the negative charge on the anion, larger is the ionic radius

  • Atomic radius of the elements increases as one moves down the first group of the periodic table

  • Atomic radius of the elements increases as one moves down the first group of the periodic table


A.

Amongst isoelectronic species, smaller the positive charge on the cation, smaller is the ionic radius

The Atomic radius of the elements decreases across a period from left to right due to increasing in effective nuclear charge. On moving down a group, since, a number of shells increases, so atomic radius increases. Amongst isoelectronic species, ionic radius increases with increases in negative charge or decrease in positive charge. 

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12.

Which one of the following pairs is isostructural (i.e., having the same shape and hybridization)?

  • [BCl3 and BrCl3]

  • [NH3 and NO3-]

  • [NF3 and BF3]

  • [NF3 and BF3]


D.

[NF3 and BF3]

If a number of bond pairs and lone pairs are same for the given pairs, they are isostructural.



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13.

Which of the following species contains three bond pairs and one lone pair around the central atoms?

  • H2O

  • BF3

  • NH2-

  • NH2-


D.

NH2-


Thus, in PCl3 the central atom P atom three bond pairs and one lone pair.
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14.

pA and pB are the vapour pressure of pure liquid components, A and B, respectively of and ideal binary solution. If xA represents the mole fraction of component A, the total pressure of the solution will be

  • pA + xA(pB-pA)

  • pA + xA(pA-pB)

  • pB + xA(pB-pA)

  • pB + xA(pB-pA)


D.

pB + xA(pB-pA)

Total pressure, 
pT =p'A +p'B

We know that,
p'A =pAxA
p'B = pBxB
substituting the values of p'A and p'B in eq. (i)
pT = pAxA +pBxB
[xA+xB =1
xA = 1-xB or xB = 1-xA]
=pAxA +pB (1-xA)
=pAxA +pB -pBxA)

pT = pB +xA (pA-pB)


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15.

Which one of  the following statements regarding photochemical smog is not correct?

  • Carbon monoxide does not play any role in photochemical smog formation

  • Photochemical smog is an oxidising agent in character

  • Photochemical smog is formed through photochemical reaction involving solar energy

  • Photochemical smog is formed through photochemical reaction involving solar energy


D.

Photochemical smog is formed through photochemical reaction involving solar energy

Photochemical smog is formed in warm and sunny climate during day time by the action of sunlight on primary pollutants. It contains nitrogen oxides, ozone, PAN etc. , which are oxidising in nature. so, photochemical smog is an oxidising agent in character. it causes irritation in eyes and throat. 

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16.

The pair of species with t he same bond order is 

  • O22-, B2

  • O2+, NO+

  • NO, CO

  • NO, CO


A.

O22-, B2

straight sigma 1 straight s squared comma space straight sigma asterisk times 1 straight s squared comma space straight sigma 2 straight s squared comma straight sigma asterisk times 2 straight s squared comma straight sigma 2 straight p subscript straight z superscript 2 comma space straight pi 2 straight p subscript straight x superscript 2 almost equal to straight pi 2 straight p subscript straight y superscript 2 space comma space straight pi asterisk times 2 straight p subscript straight x superscript 2 almost equal to straight pi asterisk times 2 straight p subscript straight y superscript 2
Bond space order space space equals space fraction numerator straight N subscript straight b minus straight N subscript straight a over denominator 2 end fraction
left parenthesis where space straight N subscript straight b space equals space number space of space electrons space in space bonding space molecular space orbital
straight N subscript straight a space equals space number space of space electrons space in space anti minus bonding space molecular space orbital right parenthesis
straight O subscript 2 superscript 2 minus end superscript space left parenthesis 8 plus 8 plus 2 equals 18 right parenthesis
BO space equals space fraction numerator straight N subscript straight b minus straight N subscript straight a over denominator 2 end fraction space equals space fraction numerator 10 minus 8 over denominator 2 end fraction space equals 1
straight B subscript 2 space left parenthesis 5 plus 5 space equals space 10 right parenthesis space equals space straight sigma 1 straight s squared comma space straight sigma asterisk times 1 straight s squared comma space straight sigma 2 straight s squared comma straight sigma asterisk times 2 straight s squared comma straight pi 2 straight p subscript straight x superscript 1 almost equal to straight pi 2 straight p subscript straight y superscript 1 space

BO equals space fraction numerator 6 minus 4 over denominator 2 end fraction
similarly space comma space order space of semicolon

straight O subscript 2 superscript plus space equals space 2.5 comma space NO to the power of plus space equals space 3
NO space equals space 2.5 comma space CO space equals space 3
straight N subscript 2 space equals space 3 space and space straight O subscript 2 space equals 2
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17.

Which one of the alkali metals, forms only the normal oxide, M2O on heating in air?

  • Rb

  • K

  • Li

  • Li


C.

Li

Li is the alkali metal which forms only normal oxide Li2O when heated in air.

2Li +1/2 O2 ---> Li2O

sodium, when heated in air forms peroxide while heavier alkali metals form superoxide as the major product. 

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18.

A mixture of potassium chlorate, oxalic acid and sulphuric acid is heated. During the reaction which element undergoes a maximum change in the oxidation number?

  • S

  • H

  • Cl

  • Cl


C.

Cl

When a mixture of potassium chlorate, oxalic acid and sulphuric acid is heated, the following reaction occurs:

straight K with plus 1 on top Cl with plus 5 on top straight O with negative 2 on top subscript 3 space plus straight H with plus 1 on top subscript 2 straight C with plus 3 on top subscript 2 straight O with negative 2 on top subscript 4 space plus straight H with plus 1 on top subscript 2 straight S with plus 6 on top straight O with negative 2 on top subscript 4
space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space rightwards arrow space straight K with plus 1 on top subscript 2 straight S with plus 6 on top straight O with negative 2 on top subscript 4 space plus straight K with plus 1 on top Cl with negative 1 on top space plus straight C with plus 4 on top straight O with negative 2 on top subscript 2 space plus straight H with plus 1 on top subscript 2 straight O with negative 2 on top

Thus, Cl is the element which undergoes a maximum change in the oxidation state.

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19.

When Cl2 gas reacts with hot and concentrated sodium hydroxide solution, the oxidation number of chlorine changes from

  • zero to +1 and zero to -5

  • zero to -1 and zero to +5

  • zero to -1 and zero to +5

  • zero to -1 and zero to +5


B.

zero to -1 and zero to +5

When chlorine gas reacts with hot and concentrated NaOH solution, it disproportionates into Chloride (Cl-) and Chlorate (ClO3-) ions. 

3 Cl with 0 on top subscript 2 space plus space stack 6 NaOH space with Hot space and space concentrated below rightwards arrow space 5 Na Cl with negative 1 on top space plus Na Cl with plus 5 on top straight O subscript 3 space plus 3 straight H subscript 2 straight O

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20.

In which of the following compounds, nitrogen exhibits highest oxidation state?

  • N2H4

  • NH3

  • N3H

  • N3H


C.

N3H

straight a right parenthesis space stack straight N subscript 2 with straight x on top stack straight H subscript 4 with plus 1 on top
2 left parenthesis straight x right parenthesis space plus left parenthesis plus 1 right parenthesis 4 space equals space 0
2 straight x space equals space minus 4
straight x equals negative 2
space straight b right parenthesis space straight N with straight x on top stack straight H subscript 3 with plus 1 on top
straight x plus left parenthesis plus 1 right parenthesis space 3 space equals space 0
straight x equals negative 3

straight c right parenthesis stack straight N subscript 3 with straight x on top straight H with plus 1 on top space
straight x plus left parenthesis plus 1 right parenthesis 3 space equals space 0
straight x equals negative 3

straight d right parenthesis space straight N with straight x on top straight H with plus 1 on top subscript 2 straight O with negative 2 on top straight H with plus 1 on top
straight x plus left parenthesis plus 1 right parenthesis 2 space plus left parenthesis negative 2 right parenthesis space plus left parenthesis plus 1 right parenthesis space equals space 0
straight x plus 2 minus 2 plus 1 space equals 0
straight x plus 1 space equals space
straight x equals negative 1
Thus, oxidation state of nitrogen is highest in N3H.
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