Which pair of compounds will form a buffer in aqueous solution? HCN and NaCN HCl and NaOH NaCN and NaOH HCN and HCl HCl and NaCl NaCN and KCN
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.
Identify the strong acid/strong base.
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.
Identify the strong acid/strong base.
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.
Identify the strong acid or strong base.
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.
Identify the strong acid/strong base.
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.
Identify the strong acid/strong base.
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.
Answer only
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.
