Only a very dilute solution of hydrogen chloride in water can be concentrated by boiling the solution while a very concentrated solution would become less concentrated when boiled explain why?

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Solution

As, you boil concentrated HCl the concentration should increase because you are removing solvent and increasing solute in solutions this should increase concentration but friend this not happen. As HCl is a gas and if you have seen highly concentrated HCl they keep giving out fumes of HCl and also they are kept in dark bottle to reduce photodecomposition of HCl. So, when you boil HCl it starts giving out fume and reduces the concentration of soulte in solution. So, this is why thier is decrease in Concentration of solutions take place.

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Q. Explain why? [5 MARKS]
(a) Anhydrous HCl is a poor conductor while aq. HCl is an excellent conductor of electricity.
(b) Only a very dilute solution of hydrogen chloride in water can be concentrated by boiling the solution while a very concentrated solution would become less concentrated when boiled.
(c) When the stopper of a bottle full of hydrogen chloride gas is opened, there are fumes in the air.

Explain, why (or give reasons for)
(i) In the laboratory preparation of hydrogen chloride from sodium chloride, the gas can be obtained below 200°C or above. But the lower temperature is preferred.
(ii) Hydrogen chloride is not collected over water.
(iii) Hydrochloric acid cannot be concentrated above 22.2% by boiling.
(iv) HCl gas does not conduct electricity, but hydrochloric acid conducts electricity.
(v) Only a very dilute solution of hydrogen chloride in water can be concentrated by boiling the solution while a very concentrated solution would become less concentrated when boiled.
(vi) When the stopper of a bottle full of HCl gas is opened there are fumes in the air.
(vii) A solution of HCl gas in water turns blue litmus red and conducts electricity, while HCl gas dissolves in toluene and it has no effect on litmus and does not conduct electricity.
(viii) An aqueous solution of chlorine is acidic in nature.

Q. Assertion :Dilute HCl cannot be concentrated beyond a certain concentration by boiling. Reason: HCl boiling and melting point depend on the concentration or molarity of HCl in aqueous solution. They range from a very low conc of 0% HCl to values for fuming HCl at over 40% HCl.

Q. The correct relationship between the boiling points of very dilute solution of

A l C l_{3} (T_{1} K)

and

C a C l_{2} (T_{2} K)

having the same molar concentration is :

Q. correct relationship between the boiling points of very dilute solutions of

A I C I_{3} (t_{1}) a n d C a C I_{2} (t_{2})

having the same molar concentration is :

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