Acid Base Properties of Salt Solutions

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Acid Base Properties of Salt Solutions-Lab


Your goal is to experimentally determine the pH of the various salt solutions available, using a variety of indicators. You will then
calculate then pH, using the published Ka and/or Kb values.
There are six solutions you will be testing. See the diagram on the board for filling your well plate. Then you will add a drop of
indicator to each solution in order to experimentally determine the color. Complete the chart below for each solution.
Salt and
concentration
Dissociation reaction and
parent acid/base
Indicator Data
Sodium
carbonate
(0.1M)
Salt dissociation
Methyl violet-------Methyl orange –--Methyl red---------Bromothymol bluePhenolpthalein----Litmus paper--------
Parent acid:
Parent base:
Sodium
bicarbonate
(0.1M)
Salt dissociation
Parent acid:
Parent base:
Iron(III)
nitrate
(0.05M)
Ka=4.0x10-3
Sodium
acetate
(0.1m)
Salt dissociation
Parent acid:
Parent base:
Salt dissociation
Parent acid:
Parent base:
Methyl violet-------Methyl orange –--Methyl red---------Bromothymol bluePhenolpthalein----Litmus paper-------Methyl violet-------Methyl orange –--Methyl red---------Bromothymol bluePhenolpthalein----Litmus paper-------Methyl violet-------Methyl orange –--Methyl red---------Bromothymol bluePhenolpthalein----Litmus paper--------
Expt
determined
pH
Acid or Base Reaction
Calculation based pH
 Use App D for Ka/Kb values.
 Show all work!
Ammonium
chloride
(0.1M)
Salt dissociation
Parent acid:
Parent base:
Sodium
chloride
(0.1M)
Salt dissociation
Parent acid:
Parent base:
water
xxxxxxxxxxxxxxxxxxx
Methyl violet-------Methyl orange –--Methyl red---------Bromothymol bluePhenolpthalein----Litmus paper-------Methyl violet-------Methyl orange –--Methyl red---------Bromothymol bluePhenolpthalein----Litmus paper-------xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
A few questions:
1) Consider the difference in the pH (both expt and calculated) for the carbonate and bicarbonate solutions. Explain their difference
pH in terms of Ka/Kb values.
2) Which ions are always spectators in A/B chemistry? Put this in terms of the parent acid and base.
3) Which ions from a salt tend to increase the pH of a solution? Put this in terms of the parent acid and base.
4) Which ions from a salt tend to decrease the pH of a solution? Put this in terms of the parent acid and base.
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