Question

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.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Dilute HCl is a solution of HCl gas in water.

(i) At $20{}^{o}C$ and $1013$ mbar the maximum concentration achievable is $39.1\%$ (i.e. 100g of a concentrated HCl solution in water will contain 39.1g of HCl).

(ii) At boiling point (${110}^{o}C$) the equilibrium concentration is $20\%$ HCl. So, heating a solution of concentrated HCl (typically $36.5\%$) to ${110}^{o}C$ will cause HCl gas to be removed until its concentration in solution reaches $20\%$.
In both the above cases the concentration and boiling point are dependable. The maximum concentration achievable is $40\%$.
Hence, Both Assertion and Reason are correct and Reason is the correct explanation for Assertion