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 Multiple Choice QuestionsMultiple Choice Questions

241.

The aqueous solution of an unknown sodium salt gives the following reactions.

I. It decolourises a solution of iodine in potassium iodide.

II. It gives white turbidity with dil.HCl solution.

III. It gives a white precipitate with AgNO3 solution which changes colours and finally becomes black on standing.

The unknown sodium salt is

  • Sodium thiosulphate

  • sodium bisulphite

  • sodium sulphite

  • sodium sulphide


242.

Which of the following would exert maximum osmotic pressure?

  • Decinormal aluminium sulphate

  • Decinormal barium chloride

  • Decinormal sodium chloride

  • A solution obtained by mixing equal volumes of (b) and (c) and filtering


243.

The one which has least iodine value is

  • sunflower oil

  • ginger oil

  • ghee

  • groundnut oil


244.

The vapour pressure of 100g water reduces from 3000 Nm-2 to 2985 Nm-2 when 5g of substance 'X' is dissolved in it. Substance 'X' is

  • methanol

  • glucose

  • carbon dioxide

  • cannot predict


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245.

The solubility of saturated solution of Ag2CrO4 is s mol L-1. What is its solubility product?

  • 4s3

  • s3

  • 2s3

  • 16s2


246.

The number of phase in a colloidal system is

  • 1

  • 2

  • 3

  • 4


247.

Steel is heated to below red heat and then, cooled slowly. The process refers to

  • hardening

  • annealing

  • tempering

  • nitriding


248.

Which does not give a precipitate with AgNO3 solution?

  • [Co(NH3)6]Cl3

  • [Co(NH3)5Cl]Cl2

  • [Co(NH3)4Cl2]Cl

  • [Co(NH3)3Cl3]


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249.

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


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250.

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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