Gravimetric Analysis - ANACHEM Lesson 3 PDF

Pamantasan ng Lungsod ng Valenzuela College of Education – Science Department GRAVIMETRIC ANALYSIS Mr. Jerome R. Delos Santos January 31, 2025 – 5:00 PM – 8:00 PM Objectives: 1.Define gravimetric analysis and precipitation gravimetry; 2.Determine...

Pamantasan ng Lungsod ng Valenzuela College of Education – Science Department GRAVIMETRIC ANALYSIS Mr. Jerome R. Delos Santos January 31, 2025 – 5:00 PM – 8:00 PM Objectives: 1.Define gravimetric analysis and precipitation gravimetry; 2.Determine the advantages and disadvantages of this technique; 3.Describe the steps involved in performing gravimetric analysis.; 4.Define and solve gravimetric factor; and 5.Solve problems involving gravimetric analysis.  ANALYTE A chemical constituent or substance that is the subject of chemical analysis.  GRAVIMETRIC ANALYSIS A quantitative method in analytical chemistry that determines the amount of a specific analyte based on its mass. Precipitation Gravimetry Analyte is separated from a solution of the sample as a precipitate and is converted to a compound of known composition that can be weighed.  Steps Involved in Gravimetric 1. Preparation Analysis of Sample: A known weight of the sample is dissolved in a suitable solvent. 2. Precipitation: A reagent (precipitant) is added to the solution to form an insoluble precipitate from the analyte. 3. Filtration: The precipitate is separated from the solution using filtration 4. Washing: The precipitate is washed to remove impurities. 5. Drying: The washed precipitate is dried to remove moisture. 6. Weighing: The mass of the dry precipitate is measured accurately. 7. Calculation: Using stoichiometric relationships, the mass percent of the analyte in the original sample is calculated.  Advantages and 1. High accuracy and Disadvantages precision when 1. Time-consuming performed correctly. and labor-intensive. 2. Minimal 2. Requires careful instrumental error; handling to avoid relies on direct mass losses during transfer measurement. and weighing 3. Cost-effective, requiring relatively simple apparatus.  Gravimetric Factor (GF) An algebraic expression that converts grams of a compound into grams of a single element. It is the ratio of the formula weight (FW) of the substance being sought to that of the substance weighed. Gravimetric Factor (GF) GF = Where: a and b are the number of moles of analyte in one mole of precipitate Probex #1: Solve for the gravimetric factor where Fe is the analyte (sought) and Fe2O3 is the precipitate (weighed). Probex #2: In a gravimetric analysis involving the determination of NaCl, the substance weighed was AgCl. What is the gravimetric factor? Probex #3: Analyte = Fe3O4 Precipitate = Fe2O3  In gravimetric analysis, we are generally interested in the percent composition by weight of the analyte in the sample, that is, The weight of the analyte can be solved using the formula: Probex #4: Calculate the weight of Barium and Chlorine present in 25.0 g of Barium chloride (BaCl2) Probex #5: A 0.4550 g solid mixture containing CaSO4 (aq.) is dissolved in water and treated with an excess Ba(NO3)2 (aq.), resulting in the precipitation of 0.6168 g BaSO4 (s). What percentage of the mixture was CaSO4? Probex #6: A 5.000 g solid sample contains an unknown amount of chloride. A chemist dissolves the solid into distilled water and then adds excess silver nitrate. After the reaction, the chemist determines that 8.086 g AgCl precipitate was produced. Determine the percentage of chloride in the original sample. Probex #7: A 0.2356 g sample containing only NaCl and BaCl2 yielded 0.4637 g of dried AgCl. Calculate the percent of each halogen compound in the sample. Probex #8: 25.0 g powder which contains Na2SO4 is dissolved in water and treated with BaCl2 to precipitate BaSO4. The precipitate is washed, dried, and weighed (5.342 g). Find the mass of Na2SO4 in the original sample. Probex #9: A 0.5662 g sample of an ionic compound containing chloride ions and an unknown metal cation is dissolved in water and treated with an excess of AgNO3. If 1.0882 g of AgCl precipitate forms, what is the percent by mass of Cl in the original compound. Probex #10: A 0.4500 g sample of impure potassium chloride was dissolved in water and treated with an excess of silver nitrate. A 0.8402 g of silver chloride was massed after digesting, collecting, washing and drying the precipitate. Calculate the percentage KCl in the original sample. Thank you!