13. Ethylene glycol is used as an antifreeze agent. Calculate the amount of ethylene glycol to be added to 4 kg of water of prevent it from freezing at -6°C. (K_f for H₂0 = 1.85 K mole^-1 kg) 

(b) Name the law or principle confirmed by the following observations :  

(i) When water is added to 0.01M aqueous solution of acetic acid the number of hydrogen ions increase.

(ii) When 96500 coulombs of electricity is passed through acidulated water, 5.6 litres of oxygen at s.t.p. is liberated at the anode.

Arrange Ag, Cr and Hg metals in the increasing order of reducing power. Given :

E° _Ag+/Ag = +0.80V    E° cr⁺³/cr = -0.74V    E° Hg²/Hg = +0.79V

In a first order reaction, 10% of the reactant is consumed in 25 minutes. Calculate :

(i) The half-life of the reaction.   

(ii) The time required for completing 17% of the reaction.

(a) Explain giving reasons why (Give equations in support of your answer):

(i) A solution of NH₄Cl and NH₄OH acts as a buffer.

(ii) Cu is precipitated as CuS while Zn is not precipitated when H₂S is passed through an acidic solution of Cu(NO₃)₂ and Zn(NO₃)₂ respectively.

(i) What is Schottky defect in a solid?

(ii) A bcc element (atomic mass 65) has a cell edge of 420 pm. Calculate its density in gms / cm³.

(i)Give Lewis’ definition for acids and bases.    

(ii) The solubility of Ag₂CrO₄ at 25°C is 8.0 x 10^-5 moles /litre. Calculate its solubility product.