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