Experiment 3: Conductimetric and Gravimetric Determination of BaSO4 Flashcards
Purpose?
Analyze conductimetric and gravimetric methods to determine the concentration of Ba(OH)2 solution.
Qualitative analysis?
What compounds/elements are present.
Quantitative analysis?
How much of a compound is present.
Flocculate?
Cause to aggregate into a mass (by heating the solution)
Experiment overview (conductimetric)?
Moniter the reaction between sulfuric acid (H2SO4) and barium hydroxide (Ba(OH)2) to determine the equivalence point and concentration of Ba(OH)2.
Overall BaSO4 equation (gravimetric)?
BaOH2(aq)+ H2SO4(aq) –> BaSO4(s) + 2H2O(l)
Cunductimetric overview?
1) As .1 M H2SO4 is added, the conductivity changes
Conductivity unit?
microsiemens per cm
mewS/cm
Gravimetric overview?
1) As H2SO4 is added, solid BaSO4 will precipitate. (must be heated)
2) From drying and weighing the precipitate we can find the amount of barium in BaSO4 and the original Ba(oh)2 solution.
For gravimetric procedure to work, the following must be true (5)….
1) Compound is pure and of known stoichiometry
2) Precipitation is complete
3) Precipitation is specific, no interacting cations
4) Solid makes large, well-formed crystals
5) Solid should have high molecular weight.
What cations could interact with precipitation? How?
strontium, mercury (I), and Lead (II). Causes higher concentration of Ba(OH)2.
Procedure gravimetric (7):
1) Add 10 ml Ba(OH)2 to 100 ml beaker
2) Add deionized water.
3) Add H2SO4 drop wise while recording volume
4) Heat titrated solution to near boil
5) use vacuum filtration
6) Clean crystals with methanol
7) Dry and weigh crystals
Why use deionized water?
Won’t affect conductivity
What is a characteristic of the equivalence point?
moles Ba(OH)2 = moles H2SO4 = moles Ba. It is also when conductivity reaches a minimum
Conductivity vs ml H2SO4 added?
V shape, bottom touches x axis, bottom is the equivalence point
