Electrogravimetric Analysis

Concept #1:

Gravimetric Analysis is a chemical analysis that involves determining the weight of an isolated product and stoichiometry is the calculations of compounds from a balanced chemical reaction.


Example #1:

Iron (III) can be oxidized by an acidic K2Cr2O7 solution according to the net ionic equation below. How many microliters of a 0.250 M FeCl2 are needed to completely react with 9.12 g of a compound containing 41.5% weight K2Cr2O7?


Electrogravimetric Analysis Calculations

Example #2:

Magnesium reacts with HCl according to the reaction below. How many grams of 5.310% by weight of aqueous magnesium are required to provide a 25% excess to react with 75.0 mL of 0.0550 M HCl.


Example #3: The amount of iron within an ore sample was determined by an oxidation-reduction titration using potassium permanganate, KMnO­4, as the titrant. A 0.5600 g sample of the ore was placed into acid and the newly freed Fe3+ was then reduced to Fe2+. The titration of this solution required 39.82 mL of 0.0315 M KMnO­4 to reach the end-point. Determine the mass percent of Fe2O3 in the sample. 

Example #4: A 0.4317 g sample of CaCO3 (MW: 100.09 g/mol) is added to flask that also contained 12.50 mL of 1.530 M HBr.

CaCO3 (aq)  +  2 HBr (aq)  → CaBr2 (aq)  +  H2O (l)  +  CO2 (g)

Additional water is then added to create a 250.0 mL of Solution A. Next 20.00 mL aliquot of solution A is taken and titrated with 0.0980 M NaOH. How many milliliters of NaOH were used?

NaOH (aq)  +  HBr (aq) → H2O (l)  +  NaBr (aq)

A 9.2476 g sample of M(OH)2 was mixed with 15.00 mL of 1.530 M HI and diluted to a final 125.0 mL of solution.

M(OH)2 (aq)  +  2 HI (aq) → 2 H2O (l)  +  MCl2 (aq)

A 12.00 mL aliquot of this diluted solution was taken and titrated with 18.23 mL of 0.0695 M NaOH.

NaOH (aq)   +  HI (aq)  → H2O (l)  +  NaCl (aq)

What is the identity of the metal representing M?