The salt of an alkali metal gives violet colour in the flame test

Subject

Chemistry

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

The correct increasing order of the acid strength of benzoic acid (I), 4-nitrobenzoic acid (II), 3,4-dinitrobenzoic acid (III) and 4-methoxybenzoic acid (IV) is

  • I < II < III < IV

  • II < I < IV < III

  • IV < I < II < III

  • IV < II < I < III


2.

Choose the correct order of decreasing basic strength of the following compounds in aqueous solution

(i) C6H5NH2

(ii) C2H5NH2

(iii) NH3

(iv) (CH3)2NH

  • (i) > (ii) > (iii) > (iv)

  • (iv) > (ii) > (iii) > (i)

  • (ii) > (i) > (iii) > (iv)

  • (iv) > (iii) > (ii) > (i)


3.

The shortest wavelength of the line in hydrogen atomic spectrum of Lyman series when RH = 109678 cm-1 is

  • 1002.7 Å

  • 1215.67 Å

  • 1127.30 Å

  • 911.7 Å


4.

Arrange the following species in the correct order of their stability

C2, Li2, O2+, He2+

  • Li2 < He2+ < O2+ < C2

  • C2 < O2+ < Li2 < He2+

  • He2+ < Li2 < C2 < O2+

  • O2+ < C2 < Li2 < He2+


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5.

Molecular formulae and shapes of some molecules are given below. Choose the incorrect match.

  • NH3 - Trigonal pyramidal

  • SF4 - Tetrahedral

  • ClF3 - T-shaped

  • PCl5 - Triginal bipyramidal


6.

If two moles of an ideal gas at 500 K occupies a volume of 41 L, the pressure of the gas is (R = 0.082 L atm K-1 mol-1)

  • 2 atm

  • 3 atm

  • 4 atm

  • 5 atm


7.

At 273 K, the density of a certain gaseous oxide at 2 atm is same as that of dioxygen at 5 atm. The molecular mass of the oxide (in g mol-1) is

  • 80

  • 64

  • 32

  • 160


8.

Which of the following are isoelectronic species?

(i) NH3

(ii) CH3+

(iii) NH2-

(iv) NH4+

Choose the correct answer from the codes given below.

  • (i), (ii), (iii)

  • (ii), (iii), (iv)

  • (i), (ii), (iv)

  • (i), (iii), (iv)


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9.

The salt of an alkali metal gives violet colour in the flame test. Its aqueous solution gives a white precipitate with barium chloride in hydrochloric acid medium. The salt is

  • K2SO4

  • KCl

  • Na2SO4

  • K2CO3


A.

K2SO4

The salt gives violet colour in the flame test, which shows the presence of potassium ion (K) in it. Further, the aqueous solution of salt gives white precipitate with BaCl2 in acidic medium, so it must contain sulphate ion (SO42-) and the precipitate is of BaSO4.

Thus, the salt is


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10.

In which one of the following the central atom is sp3 hydridised?

  • NH4+

  • BF3

  • SF6

  • PCl5


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