Question:

Which of the following combinations would not result in the formation of a buffer solution?

Updated On: Jan 30, 2025
  • $NH_3 + HCl$
  • $NH_4Cl + NH_3$
  • $CH_3COOH + NaCl$
  • $NaOH+ CH_3COOH$
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The Correct Option is B

Approach Solution - 1

Combination of $NaOH$ and $CH_3COOH$ is the mixture of alkali and acetic acid. Therefore this combination can not be buffer forming solution.
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Approach Solution -2

Ans: NaOH and CH3COOH cannot form a buffer solution. This is because, to make a buffer a weak acid with its conjugate base must be present, in the specific proportion. NaOH and a weak acid like CH3COOH does not meet the criteria.  

NaOH is a strong base. It will dissociate completely into hydroxide ions and sodium ions. If there is any weak acid present in the solution, it will be easily neutralised. 

CH3COOH on the other hand is a weak acid. It will dissociate partially and produce hydrogen ions and acetate ions. Its concentration in the solution will be low. 

When NaOH is added to acetic acid, the strong base will react with the weak acid to form water and the acetate ion (CH3COO-)

NaOH + CH3COOH → CH3COO- + H2O

Therefore, the acetic acid will be neutralised. 


 

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Concepts Used:

Buffer solutions

The buffer solution is a solution that is able to maintain its Hydrogen ion concentration (pH) with only minor changes on the dilution or addition of a small amount of either acid or base. They are used in fermentation, food preservatives, drug delivery, printing, the activity of enzymes and many more.

Buffer solutions are aqueous solutions containing a weak acid and its salt - acid buffer or a weak base and its salt - base buffer.

Types of Buffer Solution

Acidic Buffers

These solutions are used to maintain acidic environments. Also, it has acidic pH and is prepared by mixing a weak acid and its salt with a strong base. An aqueous solution of an equal concentration of acetic acid and sodium acetate has a pH of 4.74.

Alkaline Buffers

These solutions are used to maintain basic conditions. It has a basic pH and is prepared by mixing a weak base and its salt with strong acid. The aqueous solution of an equal concentration of ammonium hydroxide and ammonium chloride has a pH of 9.25.