Titrations 19.4

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# Titrations 19.4 - PowerPoint PPT Presentation

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

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### 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 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?