Copper Electrolysis Practice Cards

Vocabulary terms and definitions related to the electrolysis of aqueous copper (II) sulfate, covering experimental variables, chemical equations, and identified errors.

Electrolysis

The transformation of electrical energy into chemical energy to drive a non-spontaneous redox reaction.

Cathode (reduction)

The negative electrode where the reduction of migrating $Cu^{2+}(aq)$ cations occurs, depositing solid copper metal according to the equation $Cu^{2+}(aq) + 2e^{-} \rightarrow Cu(s)$.

Anode (oxidation)

The positive electrode where solid copper atoms lose electrons and enter the solution as ions according to the equation $Cu(s) \rightarrow Cu^{2+}(aq) + 2e^{-}$.

Faraday's First Law of Electrolysis

The principle stating that the total number of electrons transferred should remain identical if the electrical current and time are held uniform across all trials.

Independent Variable

The concentrations of aqueous $CuSO_{4}$ used in the experiment ($0.1\,M$, $0.25\,M$, $0.5\,M$, and $1.0\,M$).

Dependent Variable

The measured mass change of the copper electrodes during the electroplating process.

Controlled Variables

Factors kept constant to ensure a fair test, including voltage setting, time duration, electrode surface area, and electrode submersion depth.

Random Error

In this experiment, the inverse correlation between concentration and cathode mass gain caused by rapid copper crystal growth forming a brittle, unstable layer.

Validity

The extent to which the experiment measures what it intends to measure, influenced by controlled variables and overall experimental design.

Systematic Error

The error indicated by the anode gaining mass (e.g., $+0.07\,g$ at $0.1\,M$) instead of losing it, likely due to residual water retention or the formation of an oxide slime layer.

Oxide slime layer (CuO)

An insoluble byproduct that may form and remain bound to the anode during weighing, contributing to anomalous mass gain.

Cathode Mass Gain Result ($0.1\,M$)

A measured value of $0.57\,g$, which was the highest mass gain recorded before the concentration was increased.

Cathode Mass Gain Result ($1.0\,M$)

A measured value of $0.16\,g$, representing the lowest mass gain recorded due to crystalline instability.

What is the independant, dependant and controlled variable for the electroplating prac where we changed the concentration of copper but kept the time and voltage constant

The independent variable is the concentration of copper, the dependent variable is the mass gain of the cathode, and the controlled variables are time and voltage.

Intro

Electrolysis is a chemical process that uses an electric current to drive a non-spontaneous reaction, where oxidation occurs at the anode and reduction occurs at the cathode, in accordance with Faraday's laws of electrolysis.