LIVE Course for free

Rated by 1 million+ students
Get app now
0 votes
31 views
in Chemistry by (30.0k points)
closed by
An aqueous solution of 1M NaCl and 1M HCl is:
1. Not a buffer but pH <7
2. Not a buffer but pH > 7
3. A buffer with pH <7
4. A buffer with pH >7

1 Answer

0 votes
by (54.3k points)
selected by
 
Best answer
Correct Answer - Option 1 : Not a buffer but pH <7

Concept:

  • pH (Power of Hydrogen): The degree of acidity or alkalinity of a substance is expressed in pH value.
  • pH is a scale (0 to 14) used to specify the acidity or basicity of an aqueous solution.
  • Lower pH values of solutions represent more acidic in nature,
  • While higher pH values of solutions represent more basic or alkaline.


pH = - log [H+] For acid

pOH = - log [OH-] For base

  • Buffer solution: A buffer solution contains either a weak acid and its salt with a strong base or a weak base and its salt with strong acid. Buffers resist a change in pH when acids or bases are added to them.

  • Buffer can be classified into two types;

    • Acidic Buffer: The buffer is formed from the solution of a weak acid and its salt of a strong base. acid. Acidic buffers generally have a pH of less than 7. Example of the acidic buffer is CH3COOH and CH3COONa.

    • Basic Buffer: The buffer is formed from the solution of a weak base and its salt with a strong acid. basic buffers have a pH of more than 7. An example of a basic buffer is NH4OH and NH4Cl.

    • For buffer solution,​

\({\rm{pH}} = {\rm{pKa}} + \log \left[ {\frac{{{\rm{salt}}}}{{{\rm{acid}}}}} \right] = {\rm{pKa}}\)


Explanation:

  • Given is a solution of 1M NaCl and 1M HCl.
  • NaCl is formed by the reaction of strong base NaOH and strong acid HCl.
  • NaCl is a salt of strong acid and a strong base. whereas HCl is a strong acid.
  • When equimolar amounts of them are mixed together, they do not form a buffer because a strong acid the salt of the strong acid does not form the buffer.
  • The solution of 1M NaCl and 1M HCl cannot resist the change in pH when acid or base are added to it.
  • Also, the mixture is strongly acidic because, upon hydrolysis, NaCl gives NaOH and HCl, and HCl is also present there.
  • So there is twice the amount of HCl as compared to NaOH. This renders the solution acidic in nature.
  • Hence, the pH of the solution will be less than 7.


Hence, the correct answer is an aqueous solution of 1M NaCl and 1M HCl is not a buffer but pH < 7.

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...