An acidic buffer is obtained on mixing :
1. 100 mL of 0.1 M CH₃COOH and 100 mL of 0.1 M NaOH.
2. 100 mL of 0.1 M HCl and 200 mL of 0.1 M NaCl.
3. 100 mL of 0.1 M HCl and 200 mL of 0.1 M CH₃COONa.
4. 100 mL of 0.1 M CH₃COOH and 200 mL of 0.1 M NaOH.

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