Acid-Base Reactions

Titrations can be used in the analysis of Acid-base reactions Redox reactions H2SO4 + 2NaOH 2H2O + Na2SO4 5Fe2+ + MnO4- + 8H+ Mn2+ + 5Fe3+ + 4H2O

Neutralization Reaction acid + base salt + water HCl (aq) + NaOH (aq) NaCl (aq) + H2O H+ + Cl- + Na+ + OH- Na+ + Cl- + H2O net ionic equation for strong acids and strong bases H+ + OH- H2O

Titrant or Standard Solution (known concentration) Analyte (unknown concentration) stopcock Titration In a titration, a solution of accurately known concentration (standard) is added gradually added to another solution of unknown concentration (analyte) until the chemical reaction between the two solutions is complete.

Titration vocab mol H+ = mol OH- Equivalence point – the point at which the moles are equal mol H+ = mol OH- Indicator – substance that changes color at (or near) the end point End point—the point which the indicator used in titration changes color

When doing a titration… Be sure to add the indicator used in titration changes color and measure your titrant each run. Slowly add base to unknown acid UNTIL the indicator changes color (pink)

Strong Acid-Strong Base Titrations NaOH (aq) + HCl (aq) H2O (l) + NaCl (aq) OH- (aq) + H+ (aq) H2O (l)

The titration curve of a strong acid with a strong base.

Weak Acid-Strong Base Titrations CH3COOH (aq) + NaOH (aq) CH3COONa (aq) + H2O (l) CH3COOH (aq) + OH- (aq) CH3COO- (aq) + H2O (l) At equivalence point (pH > 7)

Example 1 9.50 mL of 0.500 M NaOH was needed to titrate 5.89 mL of nitric acid. Calculate the molarity of the acid.

2RbOH(aq) + H2SO4(aq) → 2H2O(l) + Rb2SO4(aq) Example 2 In a titration, 43.21 mL of a 0.03020 M RbOH solution is required to exactly neutralize 30.00 mL of sulfuric acid. What is the molarity of the sulfuric acid solution? 2RbOH(aq) + H2SO4(aq) → 2H2O(l) + Rb2SO4(aq) 43.21 mL RbOH 1 L 0.03020 mol RbOH 1 mol H2SO4 = 0.000652471mol H2SO4 1000 mL 2 mol RbOH 0.000652471 mol H2SO4 1000 mL = 0.02175 M H2SO4 30.00 mL 1 L

The perfect endpoint color for phenolphthalein is light pink.

This is one drop beyond the perfect equivalence point light pink.

Well beyond the perfect equivalence point light pink.