Question

Which will make basic buffer?

• A. \(50 \ mL \ of \ 0.1 \ M NaOH+25\ mL\ of \ 0.1 \ M \ CH3COOH \)
• B. \(100 mL\ of \ 0.1 \ M\ CH3COOH \ + 100 \ mL\ of \ 0.1 \ M \ NaOH\)
• C. \( 100 mL \ of 0.1 \ M \ HCl+200 \ ml \ of \ 0.1 M \ Na OH \)
• D. \(100\ mL\ of\  0.1 M HCI+100 \ mL\  of \ 0.1 \ M \ NaOH\)

Answer 1

The Correct Option is C

A buffer solution is one that can resist changes in pH upon the addition of small amounts of acid or base. A basic buffer typically consists of a weak base and its conjugate acid (often in the form of a salt). Let's evaluate each option to determine which will create a basic buffer:

1. \(50 \ mL \ of \ 0.1 \ M \ NaOH+25 \ mL \ of \ 0.1 \ M \ CH_3COOH\):
   • Here, NaOH is a strong base and CH₃COOH is a weak acid. The reaction between NaOH and CH₃COOH will not result in a buffer solution as there will be an excess of NaOH (strong base). The weak acid and strong base will neutralize each other, leaving excess NaOH, and will not form a base-conjugate salt buffer.
2. \(100 \ mL \ of \ 0.1 \ M \ CH_3COOH + 100 \ mL \ of \ 0.1 \ M \ NaOH\):
   • This mixture also results in the neutralization of the weak acid (CH₃COOH) with an equal amount of strong base (NaOH). As they are equimolar, this will predominantly lead to the formation of water and CH₃COONa (sodium acetate), which do not effectively form a buffer unless more acetate ions are present.
3. \(100 \ mL \ of 0.1 \ M \ HCl+200 \ mL \ of \ 0.1 \ M \ NaOH\):
   • In this option, HCl is a strong acid and NaOH is a strong base. Upon mixing, we have 0.1 moles of HCl and 0.2 moles of NaOH. After complete neutralization, 0.1 moles of NaOH remain unreacted, which results in an excess of base. The remaining NaOH (unreacted after neutralizing HCl) in the solution forms a basic environment, thereby creating a basic solution that can resist changes in pH upon the addition of small amounts of acid, essentially acting as a basic buffer.
4. \(100 \ mL \ of \ 0.1 \ M \ HCl+100 \ mL \ of \ 0.1 \ M \ NaOH\):
   • This mixture is perfectly neutral as it consists of equal moles of strong acid HCl and strong base NaOH. This will not result in a buffer because the acid and base fully neutralize each other.

Therefore, option 3 (\(100 \ mL \ of 0.1 \ M \ HCl+200 \ ml \ of \ 0.1 M \ Na OH\)) will result in a basic buffer due to the excess NaOH left after the reaction with HCl.