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ISC Class 12 Chemistry Solved Question Paper 2004

Short Answer Type

11.

Correct the following statements:
Ethyl acetate undergoes saponification on treatment with dilute hydrochloric acid.

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12.

Correct the following statements:
Aromatic compounds undergo nucleophilic substitution reaction.

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13.

Correct the following statements:
Isotopes have the same mass number and atomic number.

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14. Why does soda water fizz when the bottle is opened ? Name the law that explains this phenomenon.

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15. Explain nuclear fission with one example. Mention any two applications of nuclear fission.

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16. An aqueous solution containing 0.2 g of compound A in 21.7 g of water freezes at 272.814 K. If the value of K_ffor water is 1.86 K kg mol^{– 1}, calculate molecular weight of compound A.

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17. Draw the electron dot or equivalent structure of HClO₄ and name the types of bonds present.

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18. Explain the purification of common salt by bubbling hydrogen chloride gas through its solution.

The purification of common salt by bubbling hydrogen chloride gas through its solution takes place due to common ion effect.

In both the common salt (NaCl) and hydrogen chloride (HCl), the chloride ion (Cl^–) is common so the concentration of Cl^– increases on bubbling hydrogen chloride through its solution. This leads the reaction in opposite direction and common salt (NaCl) is precipitated.

$NaCl space rightwards harpoon over leftwards harpoon space Na to the power of plus space plus space Cl to the power of minus HCl space rightwards harpoon over leftwards harpoon straight H to the power of plus Cl to the power of minus$

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19. The initial rate of a reaction A + B → products is doubled when the initial concentration of A is doubled and increases eight fold when the initial concentration of both A and B were doubled. State the order of the reaction with respect to A and with respect to B. Write the rate equation.

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20. A gas cylinder of 5 litre capacity containing 4 kg of helium gas at 27°C developed a leak leading to the escape of gas into the atmosphere. If the atmospheric pressure was 1.0 atmosphere, calculate the work done by the gas, assuming ideal behaviour.

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