Post on 11-May-2015
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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?