jonah chevrier nick jiang ushhud khalid philip van-lane
TRANSCRIPT
Jonah ChevrierNick Jiang
Ushhud KhalidPhilip Van-Lane
Gravimetric Estimation of Chloride Ions
Introduction
Gravimetric Analysis is used to determine the amount of a substance
Stoichiometry is the study of the relationships between products and reactants
Gravimetric stoichiometry is the combination of gravimetric analysis and stoichiometry
Objective
Approximate the amount of Cl- ions in AgCl
AgNO3 (aq) + NaCl(aq) AgCl(s) + NaNO3(aq)
Dealing with limiting and excess reagents
Filter out the AgCl from the NaNO3
Materials Safety Goggles Distilled Water NaCl (0.117g) and AgNO3(aq)
Beaker Erlenmeyer Flask Dropper Funnel 1 piece of (Whatman) filter paper Porcelain crucible and lid Crucible tongs Ring clamp Retort stand Clay triangle Bunsen burner Accurate scale
Procedure
1. Measured mass of empty crucible
2. NaCl solution created
3. Small amounts of AgNO3 added
4. AgCl filtered using filter paper and funnel
Procedure Part 2
5. After the filter paper had dried, it was carefully placed in the crucible
6. Filter was allowed to burn; AgCl remained in the crucible
7. Found mass of AgCl
Safety Precautions Safety goggles
were worn at all times
Workspace was free of clutter
All hot materials were handled with care
All substances were handled properly
Observations – Qualitative
• Black substances remain; carbon from filter paper which had not totally dissipated
• NaCl and AgNO3 were clear, aqueous solutions
• Precipitate of AgCl formed from a double displacement reaction
Observations – Qualitative
Observations – Quantitative
Objects Weighed Mass (g)
Mass of empty crucible 10
Mass of crucible and lid 15.871
Mass of crucible and NaCl 10.117
Mass of crucible, NaCl, and lid 15.988
Mass of NaCl 0.117
Mass of crucible and AgCl 10.3191
Mass of AgCl 0.3191
Calculations
n = Number of moleculesNA
n = _ Mass _ Molar Mass
Theoretical: 0.002 molesActual: 0.002226475 moles
Theoretical: 1.2044 * 1021 moleculesActual: 1.3407843432 * 1021 molecules
Calculations Part 2
Percentage Yield | Actual / Theoretical | *100
=111.32%
Percentage of Error| (Theoretical – Actual) / Theoretical |
*100=11.32%
Discussion
Initial problem was to separate AgCl(s) from the NaNO3(aq)
Both have very high boiling points; evaporation would not be feasible
Gravimetric analysis was used for convenience
Discussion Part 2: Analytical Chemistry
Study of chemical composition of natural and artificial materials
Deals with 3 main questionsWhat chemicals are present?Characteristics of the chemicals?Quantity of the chemicals?
QuantitativeAmount of chemicals
QualititativeDetermining presence of chemicals
Analytical Chemistry Part 2
Much focus on it between the 17th and 20th centuries
First kind of instrumental analysis flame emissive spectrometryRobert Bunsen, 1860
Most studied branch of chemistry
Discussion Part 3: Thermogravimetric Analysis
Part of instrumental analysis branch
Study of weight changes in relation to temperature
Used to determine characteristics of polymersLarge molecules composed of
repeating structural units
Discussion Part 4: Volumetric Titration
Another traditional analytical technique
Reagent of known concentration and volumeTitrant
Solution of unknown volume and concentrationTitrand
Volumetric Titration Part 2
Volume, instead of mass, is measured
Titrant is added to titrand until endpoint is reachedIndicators make endpoint obvious to
observers Most often used for neutralization
reactionsAcid + Base Water + Ionic Salt
Conclusion
Precipitate of AgCl formed through double displacement reaction
AgNO3 (aq) + NaCl(aq) AgCl(s) + NaNO3(aq)
0.3191g of AgCl1.3407843432 * 1021 Cl- ions in precipitate
Carbon particles remained Added to mass
Sources of Error
Inconsistence balance readings Contamination of chemical substances Uncertain if the Cl- ions had completely
reacted with the Ag+ ions Qualitative filter paper did not
disintegrate Residue left in crucible from previous
experiments
Suggested Modifications
Use of quantitative filter paper rather than qualitative
More accurate balances Using materials which may not
have been contaminated from previous experiments