Which pair of compounds will form a buffer in aqueous solution

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Answer

General guidance

Concepts and reason
The concept used to solve this problem is that a buffer is formed by the combination of a weak acid and its salt of a strong acid or by the combination of a weak base and its salt of strong acid.

Fundamentals

A buffer solution is a solution that resists change in pH on addition of a strong base or a strong acid. Buffer solutions are of 2 types: 1. Acidic buffer- This is formed by a weak acid and its salt of strong base. 2. Basic buffer- This is formed by a weak base and its salt of strong acid.

Step-by-step

Step 1 of 6

Part A HCN is a weak acid and NaCN on the other hand is a salt of a weak acid HCN and a strong base NaOH.

Part A

HCN and NaCN form a buffer in aqueous Solution.


HCN is a weak acid and NaCN on the other hand is a salt of a weak acid HCN and a strong base NaOH. Therefore, according to definition, they form an acid buffer.

Step 2 of 6

Part B HCl is a strong acid and NaOH on the other hand is a strong base.

Part B

HCl and NaOH don’t form a buffer in aqueous Solution.


HCl is a strong acid and NaOH is a strong base. Together they form a salt NaCl.

Step 3 of 6

Part C NaOH is a strong base and NaCN on the other hand is a salt of a weak acid HCN and a strong base NaOH.

Part C

NaOH and NaCN will not form a buffer in aqueous Solution.


NaOH is a strong base and NaCN on the other hand is a salt of a weak acid HCN and a strong base NaOH. Therefore, according to definition, they don’t form a buffer.

Step 4 of 6

Part D HCl is a strong acid and HCN on the other hand is a weak acid.

Part D

HCl and HCN don’t form a buffer in aqueous Solution.


HCl is a strong acid and HCN on the other hand is a weak acid. So, they don’t form a buffer.

Step 5 of 6

Part E HCl is a strong acid and NaCl on the other hand is a salt of a strong acid HCl and a strong base NaOH.

Part E

HCl and NaCl will not form a buffer in aqueous Solution.


HCl is a strong acid and NaCl on the other hand is a salt of a strong acid HCl and a strong base NaOH. Therefore, according to definition, they don’t form a buffer.

Step 6 of 6

Part F

NaCN is a salt of a strong base and weak acid and KCN on the other hand is also salt of a weak acid and a strong base.

Part F

NaCN and KCN don’t form a buffer in aqueous Solution.


NaCN is a salt of a strong base and weak acid and KCN on the other hand is also salt of a weak acid and a strong base. So, they don’t form a buffer.

Answer

Part A

HCN and NaCN form a buffer in aqueous Solution.

Part B

HCl and NaOH don’t form a buffer in aqueous Solution.

Part C

NaOH and NaCN will not form a buffer in aqueous Solution.

Part D

HCl and HCN don’t form a buffer in aqueous Solution.

Part E

HCl and NaCl will not form a buffer in aqueous Solution.

Part F

NaCN and KCN don’t form a buffer in aqueous Solution.

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