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ISC Class 12 Chemistry Solved Question Paper 2009

Short Answer Type

11. Correct the following statements by changing the underlined part of the sentence. (Do not change the whole sentence) :

An aqueous solution of sodium sulphate is acidic in nature.

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12. Correct the following statements by changing the underlined part of the sentence. (Do not change the whole sentence) :

The solubility product of silver chloride in water decreases on the addition of potassium chloride to the solution.

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13. The boiling point of pure water is 373K. Calculate the boiling point of an aqueous solution containing 18 gms of glucose (MW = 180) in 100 gms of water. Molal elevation constant of water is 0.52 K kg mol^-1.

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14. Equal weights of two substances X and Y are dissolved in equal volumes of water. The osmotic pressure of the solution containing Y is five times the osmotic pressure of the solution containing X. What is the molecular weight of X if that of Y is 60?

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15.

Which of the following solutions will have a lower vapour pressure and why ?

(1) A 5% solution of cane sugar (C_I2H₂₂O₁₁)

(2) A 5% solution of urea (NH₂CO NH₂)

(Relative atomic masses: H = 1, C = 12, 0 = 16, N = 14).

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16. When ammonium chloride and ammonium hydroxide are added to a solution containing both Al⁺³and Ca⁺² ions, which ion is precipitated? Why?

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17. Explain why a solution of copper chloride is acidic while that of sodium chloride is neutral.

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18.
(i) In a body centred and face centred arrangement of atoms of an element, what will be the number of atoms present in respective unit cells?

(ii) Explain why graphite is soft and can be used an a lubricant.

(i) No. of atoms present in body centred arrangement in an

unit cell = No. of particle at corners + No. of particles at centre

= 8 x 1/8 + 1 x 1

= 1 + 1

= 2

No. of atoms present in face centred arrangement

in an unit cell = No. of particulars at corners + No. of particulars at faces

= 8 x 1/8 + 6 x 1/2

= 1 + 3

= 4

(ii) Graphite has layered structure. It is made of hexagonal layers of carbon atoms which are held together by weak Van-der Wall’s forces. Therefore, they can slip over each other and graphite can be used as lubricant.

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