How do you calculate the concentration of sodium hydroxide?

How can we calculate the concentration of diluted acid?

• A 50.0 mL sample of sulphuric acid was diluted to 1.00 L. A sample of the diluted sulphuric acid was analysed by titrating it with aqueous sodium hydroxide. In the titration, 25.00 mL of 1.00 M aqueous sodium hydroxide required 20.0 mL of the diluted sulphuric acid for neutralisation. 1)Calculate the concentration of the diluted acid. 2)Calculate the concentration of the original concentrated sulphuric acid solution. 3)Suggest a suitable indicator for the above titration. glad if somebody can help...appreciate it,tq

• Answer:

  Hi Dyana, 1) Calculate the concentration of the diluted acid ¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯ H2SO4 + 2 NaOH = Na2SO4 + 2 H2O . . . accordingto the equation : 2 n(H2SO4) = n(NaOH) 2 x Ca x Va = Cb x Vb Ca = Cb x Vb / (2 x Va) Ca = 1,00 x 25 / (2 x 20) Ca = 0,625 mol/L 2)Calculate the concentration of the original concentrated sulphuric acid solution. ¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯ Co x Vo = Ca x Va Co = Ca x Va / Vo Co = 0,625 x 1,00 / 0,050 Co = 12,5 mol/L 3)Suggest a suitable indicator for the above titration ¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯ pKa2 = 1,9 pH(equivalence) = pKw / 2 + pKa2 / 2 + log(SO4(2-)) / 2 pH(equivalence) = pKw / 2 + pKa2 / 2 +log(Ca x Va / (Va + Vb)) pH(equivalence) = 14 / 2 + 1,9 / 2 + log(0,625 x 20 / (20 + 25)) pH(equivalence) = 6,1 http://fr.wikipedia.org/wiki/Indicateur_de_pH BBt is a correct indicator . . . !