Question

Suppose you believe your unknown compound is NaOH, and you prepare 20 mL of a 0.1 mol/L solution of it. The stockroom provides a 0.2 mol/L HCl solution as the titrant. What volume of HCl (in mL) is needed to reach the equivalence (stoichiometric) point if your unknown compound is NaOH? NaOH(aq) + HCl(aq) --> NaCl(aq) + H2O(l)

Answer 1

Answer : Volume of HCl ( in ml)  is 10 ml.

Solution : Given,   Concentration of NaOH = 0.1 mol/L

                                Volume of NaOH = 20 ml

                                Concentration of HCl = 0.2 mol/L

                                 Volume of HCl =  ?

    Formula used :   Moles = Volume ×  Concentration

    In the reaction, we see that 1 mole of NaOH react with the 1 mole of HCl.

    so,

                       Moles of NaOH = Moles of HCl

    Moles of HCl = Moles of NaOH = Volume of NaOH ( in L) × Concentration of NaOH

    Converstion ml into L :      1000 ml = 1 L

             Moles of HCl =  $\frac{20}{1000}$ × 0.1

                                    =  0.002 mol

             Volume of HCl = Moles / Comcentration of HCl

                                       = $\frac{0.002 mole}{0.2mole/L}$

                                       =  0.01 L

             Volume of HCl (in ml) =  0.01 × 1000 = 10 ml