Use the titration results to calculate the moles of H_2 SO_4, that were used to

Question

Use the titration results to calculate the moles of H_2 SO_4, that were used to reach the equivalence point in each trial. Use your titration results to calculate the molar concentration (molarity) of the Ba (OH)_2 solution using the molar amount ofH2Soe used in each trial. Convert the mass of the barium sulfate precipitate, formed in each trial, to moles. Use the moles of BaSO_4 from 3 above to calculate the molarity of the Ba (OH)_2 solution. Compare the results of your calculations from 2 and 4 above with the actual molarity of the Ba (OH)_2 solution. Which method of analysis, equivalence point or gravimetric determination, was more accurate in your experiment? Why?

Explanation / Answer

Reaction taking place is:

Ba(OH)2 + H2SO4 ---> BaSO4 + 2H2O

(1)

Moles of H2SO4 used = Volume*Molarity = 0.00838*0.1 = 0.000838 moles

(2)

According to reaction stoichiometry, same number of moles of Barium hydroxide must be present.

So, molarity of Ba(OH)2 = moles/Volume = 0.000838/0.01 = 0.0838 M

(3)

Moles of BaSO4 formed in the experiment = Mass/MW = 0.61/233.38 = 0.00261 moles

(4)

According to reaction stoichiometry,

Moles of Barium hydroxide must be present = Moles of BaSO4 formed

So, molarity of Ba(OH)2 = moles/Volume = 0.000261/0.01 = 0.0261M

(5)

The results from (2) qnd (4) show that the conc. in (4) is much less than the conc in (2). So this method is not very accurate.

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