Q.

40 mL of a mixture of CH3COOH and HCl (aqueous solution) is titrated against 0.1 M NaOH solution conductometrically. Which of the following statement is correct
[2025]

1 The concentration of CH3COOH in the original mixture is 0.005 M.  
2 The concentration of HCl in the original mixture is 0.005 M.  
3 CH3COOH is neutralised first followed by neutralisation of HCl.  
4 Point ‘C’ indicates the complete neutralisation of HCl.  

Ans.

(2)

First NaOH reacts with HCl. Point B indicates complete neutralization of HCl. 2 mL of NaOH is used to neutralize HCl.

When NaOH completely neutralizes HCl:

mmol of NaOH=mmol of HCl

MNaOH×VNaOH(that reacts with HCl)=MHCl×VHCl

0.1×2=MHCl×40

MHCl=0.005 M

When HCl is completely neutralized, then NaOH reacts with CH3COOH.  Thus, (5−2) mL = 3 mL of NaOH reacts with CH3COOH.  Point C indicates complete neutralization of CH3COOH.

When NaOH completely neutralizes CH3COOH:

mmol of NaOH=mmol of CH3COOH

MNaOH×VNaOH (that reacts with CH3COOH)

=MCH3COOH×VCH3COOH

0.1×3=MCH3COOH×40

MCH3COOH =0.0075 M