Aqueous electrolysis: water-derived species change the products
| English | 中文 | Pinyin |
|---|---|---|
| inert electrode | 惰性电极 | duò xìng diàn jí |
| aqueous electrolyte | 水溶液电解质 | shuǐ róng yè diàn jiě zhì |
What would explain this observation?
- Aqueous sodium chloride gives hydrogen at the cathode rather than sodium. The solution contains water-derived species as well as the dissolved salt ions.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- For the specification’s inert-electrode 惰性电极 school model, hydrogen forms at the cathode if the dissolved metal is more reactive than hydrogen; a less reactive metal such as copper can form instead. At the anode, oxygen forms unless halide ions are present, when the halogen is predicted. The GCSE account describes water supplying hydrogen and hydroxide ions that can be discharged.
- aqueous electrolyte 水溶液电解质: A water-containing ionic solution used as the conducting liquid; inert electrode: An electrode not intended to react in the specified electrolysis.
Which products are predicted for aqueous copper(II) sulfate with inert electrodes?
Aqueous copper(II) chloride therefore gives copper at the cathode and chlorine at the anode. Sodium chloride solution gives hydrogen and chlorine under the approved handbook conditions. Copper(II) sulfate gives copper and oxygen, while sodium sulfate gives hydrogen and oxygen. State that these are the specified single-solute, inert-electrode predictions; concentration and electrode material can affect actual competing reactions outside this simple rule.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Aqueous copper(II) chloride therefore gives copper at the cathode and chlorine at the anode. Sodium chloride solution gives hydrogen and chlorine under the approved handbook conditions. Copper(II) sulfate gives copper and oxygen, while sodium sulfate gives hydrogen and oxygen. State that these are the specified single-solute, inert-electrode predictions; concentration and electrode material can affect actual competing reactions outside this simple rule.
- Identify the dissolved positive and negative ions, then include water-derived ions in the explanation. Apply cathode and anode rules separately. Use only school-approved dilute solutions and a low-voltage supply, with fixed electrode spacing and appropriate ventilation. Chlorine-containing observations must follow the technician-approved small-scale method; do not smell gases or generate large quantities.
Which two habits make the investigation or model in this case more defensible?
Identify the dissolved positive and negative ions, then include water-derived ions in the explanation. Apply cathode and anode rules separately. Use only school-approved dilute solutions and a low-voltage supply, with fixed electrode spacing and appropriate ventilation. Chlorine-containing observations must follow the technician-approved small-scale method; do not smell gases or generate large quantities.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: four supplied solutions are CuCl₂, NaCl, CuSO₄ and Na₂SO₄ in water with inert electrodes. Two have copper cathode products and two hydrogen; two have chlorine anode predictions and two oxygen. This classification counts predictions from stated conditions, not proof of identical product rates or recovery across the four solutions.
Under the stated rules, how many of aqueous CuCl₂, NaCl, CuSO₄ and Na₂SO₄ have hydrogen cathode predictions? Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Under the stated rules, how many of aqueous CuCl₂, NaCl, CuSO₄ and Na₂SO₄ have hydrogen cathode predictions?
The result is 2 solutions. Known: four supplied solutions are CuCl₂, NaCl, CuSO₄ and Na₂SO₄ in water with inert electrodes. Two have copper cathode products and two hydrogen; two have chlorine anode predictions and two oxygen. This classification counts predictions from stated conditions, not proof of identical product rates or recovery across the four solutions.
Check the conclusion and its limits
- Dissolved chloride gives chlorine, not solid chloride ions, at the anode in the stated model. Aqueous sulfate does not produce sulfur by simply stripping its name from the formula. Do not apply the molten binary rule to water-containing solutions.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Water cannot affect products because it is absent from the written salt formula. This claim is false: Dissolved chloride gives chlorine, not solid chloride ions, at the anode in the stated model. Aqueous sulfate does not produce sulfur by simply stripping its name from the formula. Do not apply the molten binary rule to water-containing solutions.
Aqueous electrolysis: water-derived species change the products: Aqueous copper(II) chloride therefore gives copper at the cathode and chlorine at the anode. Sodium chloride solution gives hydrogen and chlorine under the approved handbook conditions. Copper(II) sulfate gives copper and oxygen, while sodium sulfate gives hydrogen and oxygen. State that these are the specified single-solute, inert-electrode predictions; concentration and electrode material can affect actual competing reactions outside this simple rule.
Water cannot affect products because it is absent from the written salt formula.
Dissolved chloride gives chlorine, not solid chloride ions, at the anode in the stated model. Aqueous sulfate does not produce sulfur by simply stripping its name from the formula. Do not apply the molten binary rule to water-containing solutions.
A water-containing ionic solution used as the conducting liquid: write the technical term.
aqueous electrolyte means A water-containing ionic solution used as the conducting liquid.