An aqueous solution of 1M NaCl and 1M HCl is:

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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

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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.