Determine the concentration of silver ions in an unknown solution. Precipitate the silver as silver chloride, weigh the dried solid, and work back to the moles and concentration of Ag⁺ — then confirm it by a precipitation titration. In each section, calculate your answer first, then check it against the experiment.
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Theory — Gravimetric Analysis
The Idea of Gravimetric Analysis
Gravimetric analysis finds the amount of a substance by converting it into a solid of known composition, then weighing that solid. To find silver ions, chloride is added so the silver precipitates as insoluble silver chloride, AgCl. The precipitate is filtered, dried, and weighed.
% Cl in a sample = (mass Cl in AgCl ÷ sample mass) × 100
Precipitation Titration
The same 1:1 reaction can be used as a titration: a standard silver nitrate solution is added to a chloride sample until all the chloride has reacted (the equivalence point). At that point the moles of Ag⁺ added equal the moles of Cl⁻ present.
Ag⁺ + Cl⁻ → AgCl(s); an insoluble solid that can be filtered and weighed.
Mole Bridge
1 mol AgCl = 1 mol Ag⁺. The weighed solid gives the moles directly.
Constant Mass
Dry the precipitate to constant mass before weighing for an accurate result.
Species
Molar mass (g/mol)
AgCl
143.32
Ag
107.87
Cl
35.45
AgNO₃
169.87
Apparatus
The equipment a real gravimetric-analysis experiment uses. In the simulation these are modelled for you, but the readings correspond to what each instrument would measure.
Filter funnel
Separates the precipitate from the solution.
Crucible & tongs
Holds the precipitate while it is dried or ignited.
Analytical balance
Weighs the dried precipitate to find the analyte mass.
Desiccator
Cools the sample without absorbing moisture before weighing.
Drying oven / hot plate
Drives off water to constant mass.
Beaker
Where the precipitate is formed from the reagents.
Instructions — Running the Virtual Experiment
The simulation has three sections. In each one, calculate the answer yourself first, then run the experiment to check it, and record both values in your lab report with screenshots.
Part 1 — Precipitate & Weigh (Gravimetric tab)
1
Open Simulation → Gravimetric. Choose an unknown Ag⁺ sample and its volume, then add excess chloride and click Precipitate & weigh to obtain the mass of dry AgCl.
2
Calculate [Ag⁺] yourself from the weighed AgCl (moles AgCl → moles Ag⁺ → divide by volume), then compare with the value the experiment reports. Record the AgCl mass, your calculated [Ag⁺], and the lab value.
Part 2 — Percent Chloride (% Cl tab)
1
Open % Cl. Enter the mass of a sample and the mass of AgCl obtained from it. Calculate the percent chloride yourself first (mass of Cl in the AgCl ÷ sample mass × 100), then check.
Part 3 — Precipitation Titration (Titration tab)
1
Open Titration. Set the standard AgNO₃ concentration, the chloride sample volume, and the volume of AgNO₃ added to reach the equivalence point. Calculate [Cl⁻] yourself first with M(Ag⁺)V(Ag⁺) = M(Cl⁻)V(Cl⁻), then check.
Weigh the precipitate, work out [Ag⁺], type it, then check.
Reaction
Cl⁻ in sample + Ag⁺ → AgCl(s)↓ All the chloride ends up as AgCl
How to find % chloride
mass Cl = (35.45 ÷ 143.32) × mass AgCl
% Cl = (mass Cl ÷ sample mass) × 100
Determine the percent chloride in a weighed solid sample
Step 1 — choose a fixed sample
Given in the experiment
Mass of sample— g
Mass of AgCl obtained— g
Step 2 — calculate, then check
mass of Cl—
Your % Cl—
Correct % Cl—
Work out the percent chloride, type it, then check.
Reaction
Ag⁺(aq) + Cl⁻(aq) → AgCl(s)↓ At the equivalence point, mol Ag⁺ added = mol Cl⁻ present (1 : 1)
How to find [Cl⁻]
mol Ag⁺ = M(AgNO₃) × V(AgNO₃ in L)
[Cl⁻] = mol Ag⁺ ÷ V(Cl⁻ in L)
Add AgNO₃ to the chloride sample
Step 1 — choose a fixed titration
Measured in the experiment
AgNO₃ conc.— M
Cl⁻ volume— mL
AgNO₃ at equivalence— mL
Step 2 — calculate, then check
mol Ag⁺ = mol Cl⁻—
Your [Cl⁻]—
Correct [Cl⁻]—
Titrate, work out [Cl⁻], type it, then check.
Team Questions
Question 1. A precipitate of AgCl weighs 0.2867 g. How many moles of AgCl is that? (Molar mass 143.32; type to 5 decimals, e.g. 0.00200)
Question 2. How many moles of Ag⁺ were in the sample that gave 0.00200 mol of AgCl? (1:1 ratio)
Question 3. If those 0.00200 mol of Ag⁺ came from a 50.0 mL (0.0500 L) sample, what is [Ag⁺]? (Type to 4 decimals)
Question 4. What mass of Ag⁺ is in 0.00200 mol of silver? (Molar mass 107.87; type in g to 4 decimals)
Question 5. A 0.300 g sample gives 0.500 g of AgCl. What is the percent chloride? (mass Cl = (35.45/143.32)×0.500; type % to 1 decimal)
Question 6. In a titration, 24.0 mL of 0.100 mol/L AgNO₃ reaches the equivalence point with 25.0 mL of chloride. What is [Cl⁻]? (Type to 4 decimals)
Question 7 — Challenge. Why must the AgCl precipitate be dried to constant mass before weighing? (Answer in a phrase)
Example Lab Report
Sample report demonstrating the expected format. Include your weighed precipitate data, the full calculation of [Ag⁺], and the titration check, with labelled screenshots.
To determine the concentration of silver ions in an unknown solution by precipitating the silver as silver chloride, weighing the dry precipitate, and calculating [Ag⁺], then confirming the result by precipitation titration.
Theory
Silver ions react with chloride to form insoluble AgCl. Because 1 mole of AgCl contains 1 mole of Ag⁺, weighing the dry precipitate gives the moles of silver, and dividing by the sample volume gives the concentration.
Titration check: 0.100 mol/L AgNO₃, 20.0 mL to reach equivalence with 50.0 mL sample → [Ag⁺] = (0.100 × 20.0)/50.0 = 0.0400 mol/L, matching the gravimetric result.
Analysis
The gravimetric and titration methods gave the same concentration of silver ions, confirming the result. The 1:1 mole relationship between AgCl and Ag⁺ is the key bridge from the weighed mass to the concentration. Sources of error include incomplete precipitation, loss of solid during filtering, or weighing before the precipitate was fully dry.
Conclusion
The concentration of silver ions in the unknown was determined to be 0.0400 mol/L by gravimetric analysis, confirmed by precipitation titration. Gravimetric analysis is an accurate way to find an ion concentration because it relies only on a mass measurement and a known mole relationship.
Practice Questions
Show all work. Molar masses: AgCl 143.32, Ag 107.87, Cl 35.45 g/mol. Use mol = mass/molar mass and [Ag⁺] = mol/volume.
Question 1
A 25.0 mL silver sample gives 0.3583 g of dry AgCl. Calculate the moles of Ag⁺ and the concentration [Ag⁺].
