Assuming equal concentrations of conjugate base and acid, which one of the following mixtures is suitable for making a buffer solution with an optimum pH of 3.3 - 3.4?
1) 0.1 M HCl and 0.1 M NaOH
2) 0.1 M HCl and 0.1 M HClO₄
3) 0.1 M NaOH and 0.1 M NaCl
4) 0.1 M HCl and 0.1 M NaCl