Acid – Base Titration

(titration is a neutralization reaction) 30/09/99 Titration: the progressive addition of a base to an acid or an acid to a base. It is a volumetric method of analysis used to find the concentration of an acid or base. NaOH + HCl  H2O + NaCl (titration is a neutralization reaction) Endpoint: the point when the indicator colour changes (usually at the end of the titration) Equivalence point: The point when the number of equivalents mixed together are the same (in acid-base titrations equivalents refer to the number of moles of H+ and OH–)

Titration Formula #H x MA x VA = #OH x MB x VB 30/09/99 #H x MA x VA = #OH x MB x VB MA = concentration of acid MB= concentration of base VA = volume of acid VB = volume of base #H = the number of H’s in the acid #OH = the number of OH’s in the base

Titration problems What volume of 0.10 mol/L NaOH is needed to neutralize 25.0 mL of 0.15 mol/L H3PO4? 25.0 mL of HCl(aq) was neutralized by 40.0 mL of 0.10 mol/L Ca(OH)2 solution. What was the concentration of HCl? A truck carrying sulfuric acid is in an accident. A laboratory analyzes a sample of the spilled acid and finds that 20 mL of acid is neutral-ized by 60 mL of 4.0 mol/L NaOH solution. What is the concentration of the acid?

Titration problems 1. (3)(0.15 M)(25 mL) = (1)(0.10 M)(VB) VB= (3)(0.15 M)(25 mL) / (1)(0.10 M) = 112.5 mL 2. (1)(MA)(25 mL) = (2)(0.10 M)(40 mL) MA= (2)(0.10 M)(40 mL) / (1)( 25mL) = 0.32 M 3. Sulfuric acid = H2SO4 (2)(MA)(20 mL) = (1)(4.0 mol/L)(60 mL) MA = (1)(4.0 M)(60 mL) / (2)(20 mL) = 6.0 M