To verify Faraday's first law of electrolysis by measuring the mass of copper deposited on the cathode of a copper voltameter as a function of total electric charge, determine the electrochemical equivalent of copper (Z) and the Faraday constant (F), and estimate Avogadro's number. Explore a virtual apparatus, collect readings and analyse a graph.
Ready for a virtual observation.
Adjust the apparatus, then take a reading.
Timing is generated from the model; a short on-screen trial represents a longer physical interval. Animation is illustrative.
Calculations assume 100% current efficiency with zero hydrogen gas co-evolution, negligible cuprous ion (Cu⁺) intermediate formation, and ideal analytical balance precision without atmospheric oxidation. Real voltameter deposits can suffer mass loss if spongy dendrites flake off during washing or mass gain if residual sulfate salts are incompletely rinsed or if high-temperature drying oxidizes copper into Cu₂O.
Provides a heavy-walled glass electrolytic vessel with an insulating crossbar supporting two outer electrolytic copper anode plates and a central removable cathode plate immersed in acidified copper sulfate electrolyte solution.
Measures the mass of the clean, dry copper cathode plate before and after electrolysis with 0.0001 g (0.1 mg) resolution and high repeatability.
Provides an adjustable, filtered direct-current source (0–30 V, 0–3 A) paired with a heavy wirewound rheostat to maintain a strictly constant current (I = 1.000 A) throughout each deposition trial.
Measures and monitors the electrolysis current with 0.001 A resolution (accuracy ±0.2%) to verify constant charge delivery rate.
Times the duration of electrolysis with 0.01 s precision, enabling exact computation of the total electrical charge Q = I · t.
Supplies distilled water wash bottles, high-purity ethanol rinsing baths, and a warm-air desiccator to rinse and dry the deposited copper cathode without surface oxidation prior to weighing.
To verify Faraday's first law of electrolysis by measuring the mass of copper deposited on the cathode of a copper voltameter as a function of total electric charge, determine the electrochemical equivalent of copper (Z) and the Faraday constant (F), and estimate Avogadro's number. Suggested independent settings: 600.0, 1200.0, 1800.0, 2400.0, 3000.0, 3600.0 C.
Clean the copper cathode plate thoroughly using fine emery cloth to remove any oxide film, rinse in distilled water, dip in pure ethanol, and dry gently in a warm-air stream. Once cooled to room temperature, weigh the dry cathode plate on the four-decimal analytical balance and record its initial tare mass m₀ to the nearest 0.0001 g.
A spotless metallic surface free of grease and oxide is essential for uniform crystalline adherence of deposited copper, while exact initial mass determines the net deposited gain.
Connect the circuit in series: DC power supply positive terminal to the voltameter anode plates, central cathode terminal to the digital ammeter, and ammeter through the rheostat and knife switch back to the negative terminal. Insert a dummy test plate, close the switch, adjust the rheostat until the current reads exactly I = 1.000 A, then open the switch and replace the dummy with the weighed cathode.
Pre-adjusting the current with a sacrificial plate ensures that the experimental cathode experiences a perfectly constant current from the exact moment the circuit is energized.
Simultaneously close the knife switch and start the digital chronometer. Monitor the ammeter continuously, making micro-adjustments to the rheostat if needed to maintain current at precisely 1.000 A. Run the electrolysis for an initial duration of 10.0 minutes (t = 600 s, delivering charge Q = 600 C), then open the knife switch and stop the timer simultaneously.
Simultaneous switching and timing guarantees that total electric charge Q = I · t is recorded with negligible timing latency error.
Carefully remove the cathode by its stem, handling it only by the dry upper clamp edge. Gently rinse it in a gentle stream of distilled water, immerse in ethanol to displace residual water, and dry in a desiccated warm-air stream for 3 minutes. Allow it to reach thermal equilibrium, weigh on the analytical balance, and record final mass m₁.
Ethanol displaces water and evaporates rapidly, preventing the warm moist copper from oxidizing into cuprous or cupric oxides that would inflate the measured mass.
Repeat the electrolysis procedure for cumulative durations of 20.0 min (1200 C), 30.0 min (1800 C), 40.0 min (2400 C), 50.0 min (3000 C), and 60.0 min (3600 C), cleaning, drying, and re-weighing the cathode after each run to record the net deposited copper mass m = m₁ − m₀.
Sampling six evenly spaced charge levels spanning 600 C to 3600 C provides robust statistical leverage across the entire working domain.
Tabulate the total charge Q (in Coulombs) on the horizontal axis and the deposited copper mass m (in grams) on the vertical axis. Compute ordinary least-squares regression to determine slope Z and intercept b. Calculate the Faraday constant as F = M / (2Z) and Avogadro's number as N_A = F / e.
Linear regression over all six charge levels averages out microbalance rounding and washing losses, yielding an unbiased estimate of the electrochemical equivalent Z.
Points are your observations. The fit uses SI x and y values before display scaling.
| # | Electric charge Q (C) | Deposited copper mass m (g) | Electric charge Q (C) | Deposited copper mass m (g) | Remove |
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