1 Solution Stoichiometry Solution Stoichiometry uses molarity as a conversion factor between volume...
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Transcript of 1 Solution Stoichiometry Solution Stoichiometry uses molarity as a conversion factor between volume...
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Solution StoichiometrySolution Stoichiometry
• Solution Stoichiometry uses molarity as a conversion factor between volume and moles of a substance in a solution.
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TitrationsTitrations
Titration: A technique for determining the concentration of
a solution by measuring the volume of one solution needed
to completely react with another solution.
This is a special case of a Limiting Reagent!
Usually the reaction of an acid with a base.
TitrationsTitrations
Analyte: the solution of unknown concentration but known
volume.
Titrant: the solution of known concentration.
Process: Add titrant until all of the analyte has reacted, then
record the volume of titrant added.
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Analyte + Titrant → Products
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TitrationsTitrations
Equivalence Point: the point at which exactly the right
volume of titrant has been added to complete the reaction.
Indicator: substance that changes color when an excess of
titrant has been added (phenolphthalein, bromocresol
green).
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PhenolphthaleinPhenolphthalein
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Methyl OrangeMethyl Orange
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Delivery of TitrantDelivery of Titrant
• Adding titrant drop-wise.• How many drops fit into 1mL?
• Process: Calibration-hold the pipette in the VERTICAL position and deliver the titrant into a graduated cylinder while counting every drop.
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Copy the following “Data Tables”Copy the following “Data Tables”
VinegarMeasurement Value
Analyte
Volume
Titrant
Molarity
Calibration
Volume
Indicator
Acid
Base
Reaction
Mole Ratio
AntacidMeasurement Value
Analyte
Quantity
Titrant
Molarity
Calibration
Volume
Indicator
Acid
Base
Reaction
Mole Ratio9
1.00M
10mL
NaOH
phenolphthalein
Colorless
Vinegar
Pink
3.00M
Methyl orange
Pink
Yellow
1tablet in 20mL H2O
HCl
Antacid
____drops ____mL ____drops ____mL
Titrations CalculationsTitrations Calculations
1. Find the number of moles of titrant added to reach the endpoint.
2. Determine the moles of analyte that must have been present (use stoichiometric coefficients).
3. Determine the concentration of analyte that must have been present in the flask (use the volume of analyte).
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TitrationsTitrations
Example #1: 14.84 mL of an HCl solution of unknown
concentration is titrated with standard NaOH solution. At
the equivalence point, 25.0 mL of the 0.675 M NaOH has
been added. Calculate the concentration of the HCl
solution.
NaOH + HCl → NaCl + H2O
Hints: Titrant = ?moles Analyte = ?moles ?Liters
Answer = 1.14 M
StoichiometryStoichiometry
Measurement Calculation
moles of titrant
moles of analyte (use stoichiometric coefficients).
concentration of analyte
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