Calculations involving neutralization reactions Titrations 19.4 Calculations involving neutralization reactions

Learning Objectives Understand the neutralization reaction … strong acid and base reaction Concept of titration, end point, and equivalence point and how they relate to neutralization reaction How to solve titration problems … how to determine unknown acid or base concentration

Neutralization Reaction Acid + Base  Salt + Water Called a neutralization reaction Is a double replacement reaction Requires use of an indicator to identify neutralization point Strong acid + Strong base = neutral solution If # of H+ = # of OH-

Titration A titration is a reaction where a solution of known concentration (standard solution) is used to identify a solution of unknown concentration

Practical Examples of Titrations Determining blood glucose levels. Determination of medical proportions in a IV drip. Amount of salt and sugar in food. Level of acidity in wine and cheese. Level of acidity in fresh water samples.

End Point The end point of a titration is when the solution just barely changes color The equivalence point is the point where the acid and base exactly react with one another Ideally, the end point should be the same as the equivalence point

Titration Calculation In a titration, 27.4 ml of a 0.0154 M HCl solution is added to 20.0 mL sample of NaOH solution of unknown concentration. What is the molarity of the basic solution? HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq) SA SB Neutralization First we need to figure moles of HCl used to neutralize NaOH in reaction. 0.0274 L x 0.0154 mol/L = 4.22 x 10-4 mol of HCl

Titration Calculation = 4.22 x 10-4 mol of HCl HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq) = 4.22 x 10-4 mol of NaOH M of NaOH = 4.22 x 10-4 mol of NaOH .0200 L M of NaOH = .021 M

Titration Endpoint How can you tell when you have added enough NaOH?

Titration Curve

Titration Calculation Shortcut Objective: to find the M of the unknown acid or base. Use a balanced chemical equation to determine the mole/mole ratio of acid to base. MaVana=MbVbnb M = molarity V = volume n = # of H3O+ ions in the acid or OH- ions in the base. (if there are no OH- ions in the base, n = 1)

Cool Down How many moles of sulfuric acid are required to completely neutralize 0.50 mol of sodium hydroxide? How many moles of potassium hydroxide are needed to completely neutralize 1.56 mol of phosphoric acid?