Examkin

Question

Difficulty: EasyAnalyzing Experimental Procedures and Apparatus

Experiment 1

A student constructs an electrolytic cell apparatus to measure the rate of copper electroplating. As shown in the setup, a nickel cathode strip is submerged in an aqueous 1.0 M CuSO41.0\text{ M } \text{CuSO}_4 solution alongside a copper anode. Both electrodes are connected to a DC power supply and an ammeter. Before turning on the power supply, the student thoroughly washes the nickel cathode with distilled water and acetone, allows it to dry completely, and measures its mass on an analytical balance.

What is the primary procedural purpose of drying the nickel cathode completely before recording its initial mass?

  1. To ensure that residual solvent weight does not inflate the baseline mass measurement.Answer
  2. B
    To prevent the copper anode from dissolving into the electrolyte solution when current flows.
  3. C
    To increase the electrical conductivity of the cathode surface before applying voltage.
  4. D
    To maintain a constant concentration of copper ions in the electrolyte bath during the trial.

Answer

The primary procedural purpose of drying the nickel cathode completely before measuring its mass is to ensure that residual solvent weight does not inflate the baseline mass measurement.
In experimental procedure analysis, cleaning and drying a solid substrate before recording its initial mass ensures that extraneous mass from washing liquids (like water or acetone) is not included in the baseline measurement. Without complete drying, the initial mass would be artificially high, resulting in an inaccurate calculation of the mass of copper plated onto the cathode.

Step-by-Step Solution

1
Identify the variable being measured in the electroplating experiment.
The student intends to determine the mass of copper plated onto the cathode by taking the difference between the final mass and initial mass of the cathode.
Accurate mass difference calculations require precise initial and final mass measurements of the metal electrode alone.
2
Analyze the impact of remaining liquid/solvent on the initial balance measurement.
If solvent remains on the electrode during the initial weighing, the recorded baseline mass will be higher than the true mass of the nickel strip.
Any liquid mass added to the initial measurement leads to an underestimation of the actual mass of copper deposited during electrolysis.
3
Evaluate the procedural step of drying the electrode.
Drying removes liquid solvent so that only the mass of the dry nickel cathode is recorded.
This establishes a clean, accurate baseline measurement free of confounding mass variables.

Key Concept

Establishing an accurate baseline measurement in gravimetric procedural design
Estimated Time:45s
Rate this question

Topics

Analyzing Experimental Procedures and Apparatus

More questions from this topic