General Chemistry LaboratoryUniversity of Kentucky

Acid-Base Acid-Base TitrationTitration

TitrationTitration

Analyte – the substance with an unknown value concentration that needs to be found

Standard – a substance with a known concentration that can be used to determine the unknown value of the analyte

Acid-Base TitrationAcid-Base Titration

acid + base salt + water

HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq)

H+ (aq) + OH-(aq) H2O(l)

H2SO4 (aq) +2NaOH (aq) Na2SO4 (aq) + 2H2O

Why is this considered a neutralization titration?

Analyte ConcentrationAnalyte Concentration

Equivalence Point – the point in an acid-base titration when the moles of H+ equals the moles of OH-

H+ (aq) + OH-(aq) H2O(l)

Equivalence PointEquivalence Point

pH sensor – a device that measures pH

Indicator – a solution that changes colors with a change in pH

Why is the determination of the equivalence point important?

PROCEDURE HINTS!PROCEDURE HINTS!

Should have 3 good sets of dataLook at your graphs before you leave

the lab Be sure to rinse the sensor well

between trials Be careful with pH sensors, they are

fragile and expensive

When the pH sensor is returned be sure the tip is submerged completely in the storage solution and that it is standing upright.

Data AnalysisData Analysis The second derivative will appear on the

screen. Use the information from this graph and the

instructions in the procedure (#14) to determine the equivalence point

Determine the HCl concentration for each trial, then average the values of the concentration.

STOICHIOMETRY!!!STOICHIOMETRY!!!

Solving a problem in an acid-base titration is similar to other stoichiometry problems

Start with a balanced chemical equation

Use the mole ratios to determine the amount, concentration, etc.

How To Determine ConcentrationHow To Determine Concentration

14.5 mL of 0.50 M NaOH are required to completely neutralize 25. mL of HCl. What is the concentration of the HCl solution?

M 0.29 L 0.025

mol 0.00725

volume

HCl mol HCl ofion Concentrat

HCl mol 0.00725 NaOH mol 1

HCl mol 1

mL 1000

mol 0.5 NaOH ml 5.14

HCl + NaOH NaCl + H2O

Practice Question #1Practice Question #1

What is the stoichiometric ratio between base and acid in the following reactions?

Hint: Balance the equations first.

1. NaOH + HCl NaCl + H2O

2. NaOH + H2SO4 Na2SO4 + H2O

3. NaOH + H3PO4 Na3PO4 + H2O

4. Ba(OH)2 + HCl BaCl2 + H2O

5. Ba(OH)2 + H3PO4 Ba3(PO4)2 + H2O

Practice Question #2Practice Question #2

A solution contains 30.00 g of NaOH in 1000. ml of solution. What is the molarity of the solution?

Practice Question #3Practice Question #3

How many ml of 0.10 M HCl would be required to neutralize 30ml of 0.10 M KOH?

30 mL of Ca(OH)2?