Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

21.

Names of some compounds are given. Which one is not correct in IUPAC system?

  • CH3 - CH(OH) -CH(CH3) - CH33-methyl-2-butanol

  • CH3 - C C - CH(CH3)4-methyl-2-pentyne

  • CH3 - CH2 - C(CH2) - CH(CH3) -CH32-ethyl-3methyl-but-1-ene


22.

The best method for the separation of naphthalene and benzoic acid from their mixture is

  • chromatography

  • crystallisation

  • distillation

  • sublimation


23.

At 25°C, the dissociation constant of a base, BOH, is 1.0 x 10-12. The concentration of
hydroxyl ions in 0.01 M aqueous solution of the base would be

  • 2.0 x 10-6 mo L-1

  • 1.0 x 10-5 mo L-1

  • 1.0 x 10-6 mo L-1

  • 1.0 x 10-7 mo L-1


24.

The aqueous solution containing which one of the following ions will be colourless ? (Atomic no. Sc= 21, Fe= 26, Ti= 22, Mn = 25)

  • Sc3+

  • Fe2+

  • Ti3+

  • Mn2+


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25.

What is the correct relationship between the pHs of isomolar solutions of sodium oxide (pH1), sodium sulphide (pH2), sodium selenide (pH3) and sodium telluride (pH4)?

  • pH1 > pH2 pH3 > pH4

  • pH1 < pH2 pH3 < pH4

  • pH1 < pH2 pH3 pH4

  • pH1 > pH2 pH3 > pH4


D.

pH1 > pH2 pH3 > pH4

The correct order of pH of isomolar solutions is

pH1 > pH2 > pH3 > pH4

sodium oxide > sodium sulphide > sodium selenide > sodium telluride.

This is because, in aqueous solution they are hydrolysed as follows:

Na2O + 2H22NaOHBase + H2O

Na2S + 2H22NaOHStrong base + H2SWeak acid  

Na2Se + 2H22NaOHStrong base + H2SeWeak acid

Na2Te + 2H22NaOH Strong base + H2TeWeak acid

Therefore, the order of acidic strength is

H2Te > H2Se > H2S > H2

Since, the pH of basic solution is higher than acidic or least basic solution.


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26.

For a first order reaction A  B, the reaction rate at reactant concentration of 0.01 M is found to be 2.0 x 10-5 mol L-1s-1. The half-life period of the reaction is

  • 220 s

  • 30 s

  • 300 s

  • 347 s


27.

Which one of the following forms micelles in aqueous solution above certain concentration?

  • Urea

  • Dodecyl trimethyl ammonium chloride

  • Pyridinium chloride

  • Glucose


28.

The rate of reaction between two reactants A and B decreases by a factor of 4, if the concentration of reactant B is doubled. The order of this reaction with respect to reactant B is

  • -1

  • -2

  • 1

  • 2


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29.

In a face-centered cubic lattice, a unit cell is shared equally by how many unit cells?

  • 8

  • 4

  • 2

  • 6


30.

A solution of urea (mol. mass 56g mol-1) boils at 100.18°C at the atmospheric pressure. If kf and kb for water are 1.86 and 0.512 K kg mol-1 respectively, the above solution will freeze at

  • -6.54°C

  • 6.54°C

  • 0.654°C

  • - 0.654°C


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