In a titration, a standard solution of hydrochloric acid (concentration 0.2 mol dm^-3) was added to 25 cm³ of a sodium hydroxide solution, concentration unknown. On addition of 18.5 cm³ HCl, the equivalence point was reached. What is the concentration of the sodium hydroxide solution?

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Quizplus · Accepted Answer

The moles of HCl added are 0.2 mol/dm³ * 18.5 cm³ * (1 dm³/1000 cm³) = 0.0037 mol. At the equivalence point, moles of NaOH = moles of HCl, so 0.0037 mol of NaOH is present in 25 cm³. The concentration of NaOH is 0.0037 mol / 0.025 dm³ = 0.148 mol/dm³.

In a Titration, a Standard Solution of Hydrochloric Acid (Concentration