Electrolysis and moving ions

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Lektionsnotizen

Big idea: electrolysis and moving ions

Key concept: Systems. Mobile positive ions move towards the negative cathode and gain electrons. Negative ions move towards the positive anode and lose electrons.
Related concepts: Models and evidence. Use a scientific explanation to make predictions, then test it against observations.
Global context: Scientific and technical innovation. Electrolysis separates elements from compounds using electrical energy.

Electrolysis Principles

Electrolysis is the breakdown of a molten or aqueous ionic compound by an electric current.
Covalent compounds and solid ionic compounds cannot undergo electrolysis because they have no free mobile ions.
Electrolyte: molten or dissolved ionic compound that conducts electricity.
Anode (positive electrode) attracts anions (negative ions).
Cathode (negative electrode) attracts cations (positive ions).
Use PANIC: Positive is Anode, Negative Is Cathode.
Electrons flow from the negative terminal of the power supply to the cathode; they do not pass through the electrolyte.
Reduction (gain of electrons) occurs at the cathode; oxidation (loss of electrons) occurs at the anode.

Ionic conductivity: solid vs molten/dissolved

Electrolysis of Molten Compounds

Molten binary ionic compounds decompose into their elements: metal at cathode, non-metal at anode.
Example: molten PbBr₂ → Pb (grey metal) at cathode, Br₂ (brown gas) at anode.
Ions must be free to move – compound must be molten (or in solution).
Electrodes must be inert (e.g., graphite or platinum) to avoid side reactions.
Half-equation at cathode: Pb²⁺ + 2e⁻ → Pb.
Half-equation at anode: 2Br⁻ → Br₂ + 2e⁻.

Electrolysis of molten lead(II) bromide

Electrolysis of Aqueous Sodium Chloride (Brine)

Brine contains Na⁺, Cl⁻, H⁺, OH⁻ ions.
At cathode: H⁺ is discharged (less reactive than Na⁺) → hydrogen gas.
At anode: Cl⁻ is discharged → chlorine gas.
Na⁺ and OH⁻ remain in solution → sodium hydroxide forms.
Industrial uses: Cl₂ → bleach; H₂ → margarine; NaOH → soap and detergents.

Electrolysis of aqueous sodium chloride (brine)

Electrolysis of Dilute Sulfuric Acid

Contains H⁺, SO₄²⁻, OH⁻ ions.
At cathode: H⁺ gains electrons → hydrogen gas.
At anode: OH⁻ loses electrons → oxygen gas (and water).
Volume of H₂ produced is twice the volume of O₂.
Gas tests: H₂ – lit splint gives 'squeaky pop'; O₂ – glowing splint relights.

Electrolysis of Aqueous Solutions

Water dissociates: H₂O ⇌ H⁺ + OH⁻ – these ions compete with solute ions.
At cathode: if metal is less reactive than hydrogen, metal is deposited; if more reactive, hydrogen gas is produced.
At anode: if halide ions (Cl⁻, Br⁻, I⁻) are present, halogen forms; otherwise oxygen from OH⁻.
Concentration matters: concentrated halide → halogen; dilute halide → oxygen.
Example: CuSO₄(aq) with graphite electrodes → Cu at cathode, O₂ at anode; blue colour fades.
With copper electrodes: anode dissolves (Cu → Cu²⁺ + 2e⁻), cathode gains mass (Cu²⁺ + 2e⁻ → Cu); solution concentration remains constant.

Ionic Half-Equations

Oxidation Is Loss (of electrons), Reduction Is Gain (OIL RIG).
REDuction at CAThode (RED CAT); ANode for OXidation (AN OX).
Metal formation: Mⁿ⁺ + n e⁻ → M (reduction).
Hydrogen formation: 2H⁺ + 2e⁻ → H₂.
Halogen formation: 2X⁻ → X₂ + 2e⁻ (oxidation).
Oxygen formation: 4OH⁻ → O₂ + 2H₂O + 4e⁻.
Half-equations must balance atoms and charges.

Summary Table of Common Electrolyses

Molten PbBr₂: anode – Br₂; cathode – Pb.
Concentrated NaCl(aq): anode – Cl₂; cathode – H₂.
Dilute H₂SO₄: anode – O₂; cathode – H₂.
CuSO₄(aq) (inert electrodes): anode – O₂; cathode – Cu.

Think like a scientist

Use a teacher-approved simulation to compare ion movement when the power supply is switched on and off.
Comparison: whether the direct-current supply is on. Outcome: ion movement and products at each electrode.
Control: keep the electrolyte and electrode materials unchanged. Explain why this makes the comparison fairer.
Evidence: Use a consistent method, repeated observations where appropriate and a table with labelled quantities and units. Keep unexpected results and investigate their cause.
Safety: Practical activities need teacher supervision and an appropriate risk assessment. Use the provided data or simulation where the investigation specifies it.
Inquiry task: State a testable question, predict the outcome using the science, then explain how your observations would support or challenge the prediction.

Evaluate the science

Electrolysis separates elements from compounds using electrical energy.
Products depend on the electrolyte, water and electrode materials; molten and aqueous electrolytes can give different products.
Evaluation task: Link your conclusion to evidence, identify a limitation and suggest a specific improvement. Distinguish a measured result from an explanation of its cause.

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Übungsfragen

Gratis-Vorschau — 8 von 52 Fragen. Registriere dich, um alle zu sehen.

1.What is the name of the process in which a molten ionic compound is broken down by an electric current?
Easy
- AElectrolysis
- BElectroplating
- CElectrorefining
- DElectrolysis of aqueous solutions
2.Which electrode is the positive electrode in an electrolysis cell?
Easy
- AAnode
- BCathode
- CElectrolyte
- DTerminal
3.What type of ion is attracted to the cathode?
Easy
- ACation
- BAnion
- CElectron
- DNeutral atom
4.During electrolysis, what happens at the anode?
Easy
- AOxidation (loss of electrons)
- BReduction (gain of electrons)
- CNo reaction
- DFormation of metal
5.In the electrolysis of molten lead(II) bromide, what is produced at the cathode?
Easy
- ALead
- BBromine
- COxygen
- DHydrogen
6.During the electrolysis of concentrated aqueous sodium chloride (brine), which gas is produced at the anode?
Easy
- AChlorine
- BOxygen
- CHydrogen
- DNitrogen
7.In the electrolysis of dilute sulfuric acid, what is the volume ratio of hydrogen to oxygen produced?
Medium
- A2:1
- B1:2
- C1:1
- D3:1
8.Which of the following is a suitable material for inert electrodes?
Easy
- AGraphite
- BCopper
- CIron
- DZinc

Mehr Fragen

9.In the electrolysis of aqueous copper(II) sulfate with graphite electrodes, what is observed at the anode?
Medium
- ABubbles of oxygen gas
- BCopper metal deposited
- CBubbles of chlorine gas
- DSolution turns green
10.What is the correct balanced half-equation for the formation of hydrogen gas at the cathode during electrolysis?
Medium
- A2H⁺ + 2e⁻ → H₂
- BH⁺ + e⁻ → H
- C2H₂O + 2e⁻ → H₂ + 2OH⁻
- DH₂O + e⁻ → H⁺ + OH⁻
11.In the electrolysis of aqueous sodium chloride, why is hydrogen produced at the cathode instead of sodium?
Medium
- ASodium is more reactive than hydrogen
- BHydrogen is more reactive than sodium
- CSodium ions are not present
- DThe solution is acidic
12.Which of the following is a use of chlorine produced during the electrolysis of brine?
Easy
- AMaking bleach
- BMaking margarine
- CMaking soap
- DMaking detergents
13.During the electrolysis of concentrated aqueous sodium chloride (brine), which product is formed at the cathode?
Easy
- ASodium metal
- BChlorine gas
- CHydrogen gas
- DOxygen gas
14.A student electrolyses dilute sulfuric acid using platinum electrodes. A gas is collected at the anode that relights a glowing splint. What is this gas?
Medium
- AHydrogen
- BChlorine
- COxygen
- DSulfur dioxide
15.Why must lead(II) chloride be molten for electrolysis to occur?
Easy
- ATo allow ions to move freely
- BTo increase the voltage
- CTo prevent side reactions
- DTo make it conduct heat
16.The half-equation for the formation of oxygen at the anode during electrolysis of dilute sulfuric acid is: 4OH⁻ → O₂ + 2H₂O + 4e⁻. How many electrons are released per molecule of oxygen?
Medium
- A2
- B4
- C1
- D8
17.In the electrolysis of molten aluminium oxide, what is the ionic half-equation at the negative electrode?
Medium
- AAl³⁺ + 3e⁻ → Al
- BAl → Al³⁺ + 3e⁻
- C2O²⁻ → O₂ + 4e⁻
- DAl³⁺ + e⁻ → Al²⁺
18.A student electrolyses dilute sodium chloride solution. Which gas is produced at the anode?
Medium
- AChlorine
- BHydrogen
- COxygen
- DSodium vapour
19.In an experiment to electrolyse molten lead(II) bromide, a student uses graphite electrodes. Which statement explains why graphite is a suitable material for the electrodes?
Medium
- AGraphite is a non-metal that conducts electricity and is inert.
- BGraphite is a metal that conducts electricity and is reactive.
- CGraphite is an insulator that does not react with the electrolyte.
- DGraphite is a covalent compound that conducts electricity when molten.
20.A student electrolyses dilute sulfuric acid using platinum electrodes. After some time, the volume of hydrogen collected is 20 cm³. What is the volume of oxygen collected under the same conditions?
Medium
- A10 cm³
- B20 cm³
- C40 cm³
- D5 cm³
21.During the electrolysis of concentrated aqueous sodium chloride (brine), a student tests the gas produced at the anode with damp litmus paper. What is the expected result?
Medium
- AThe damp litmus paper turns red and then bleaches to white.
- BThe damp litmus paper turns blue.
- CThe damp litmus paper turns red and stays red.
- DThe damp litmus paper turns green.
22.In the electrolysis of aqueous copper(II) sulfate using graphite electrodes, the blue colour of the solution fades. Which statement explains this observation?
Medium
- ACopper(II) ions are reduced to copper metal at the cathode, removing Cu²⁺ from the solution.
- BCopper(II) ions are oxidised to copper metal at the cathode, removing Cu²⁺ from the solution.
- CSulfate ions are reduced to sulfur dioxide at the anode, removing SO₄²⁻ from the solution.
- DWater molecules are reduced to hydrogen gas at the cathode, consuming H₂O.
23.Which of the following is a correct test for hydrogen gas?
Easy
- AA lit splint produces a squeaky pop.
- BA glowing splint relights.
- CDamp litmus paper turns red then white.
- DLimewater turns milky.
24.A student sets up an electrolysis cell with molten magnesium bromide. Which pair of products is formed at the electrodes?
Easy
- ACathode: magnesium; Anode: bromine
- BCathode: bromine; Anode: magnesium
- CCathode: magnesium; Anode: oxygen
- DCathode: hydrogen; Anode: bromine
25.In the electrolysis of dilute sulfuric acid, the ionic half-equation at the anode is 4OH⁻ → O₂ + 2H₂O + 4e⁻. Which statement about this half-equation is correct?
Medium
- AHydroxide ions are oxidised because they lose electrons.
- BHydroxide ions are reduced because they gain electrons.
- COxygen is produced at the cathode.
- DThe half-equation shows reduction because electrons are on the right.
26.A student electrolyses dilute barium chloride solution using inert electrodes. Which gas is produced at the anode?
Medium
- AOxygen
- BChlorine
- CHydrogen
- DBarium
27.Which of the following substances can undergo electrolysis?
Easy
- AMolten sodium chloride
- BSolid sodium chloride
- CSugar solution
- DPure water
28.In the electrolysis of molten aluminium oxide (Al₂O₃), what is the ionic half-equation at the negative electrode?
Easy
- AAl³⁺ + 3e⁻ → Al
- BAl³⁺ → Al + 3e⁻
- C2O²⁻ → O₂ + 4e⁻
- DAl + 3e⁻ → Al³⁺
29.A student uses copper electrodes to electrolyse aqueous copper(II) sulfate. Which observation is correct?
Medium
- AThe blue colour of the solution remains unchanged.
- BThe blue colour of the solution fades.
- CThe anode increases in mass.
- DOxygen gas is produced at the anode.
30.What is the definition of electrolysis?
Easy
- AThe breakdown of a molten ionic compound by an electric current
- BThe breakdown of any compound by heat
- CThe movement of electrons through a solid metal
- DThe reaction between an acid and a base
31.Complete the sentence.
Easy
In electrolysis, negatively charged ions are called ____ and are attracted to the ____.
32.State the test for hydrogen gas and the expected result.
Easy
33.Complete the ionic half-equation for the formation of oxygen gas at the anode during electrolysis of dilute sulfuric acid.
Medium
4OH⁻ → ____ + 2H₂O + 4e⁻
34.Explain why the concentration of copper(II) sulfate solution remains constant when copper electrodes are used instead of graphite electrodes for electrolysis.
Hard
35.What is the name of the negative electrode in an electrolytic cell?
Easy
- AAnode
- BCathode
- CElectrolyte
- DTerminal
36.In the electrolysis of molten lead(II) bromide, what is observed at the anode?
Easy
- AA grey solid deposits
- BBubbles of a brown gas
- CBubbles of a colourless gas
- DThe electrode dissolves
37.Which of the following is a correct test for oxygen gas?
Easy
- AA lit splint gives a squeaky pop
- BA glowing splint relights
- CDamp litmus paper turns red then white
- DLimewater turns milky
38.In the electrolysis of dilute sulfuric acid using inert electrodes, the half-equation at the anode is: 4OH⁻ → O₂ + 2H₂O + 4e⁻. Which statement about this half-equation is correct?
Medium
- AOxidation occurs because electrons are gained
- BReduction occurs because electrons are lost
- COxidation occurs because electrons are lost
- DReduction occurs because electrons are gained
39.What is the name of the negative electrode in an electrolysis cell?
Easy
- AAnode
- BCathode
- CElectrolyte
- DAnion
40.Ionic compounds in the solid state can conduct electricity.
Easy
True or false?
41.Use a teacher-approved simulation to compare ion movement when the power supply is switched on and off. What is the independent variable?
Easy
- Aion movement and products at each electrode
- Bthe number of repeated trials
- Cthe scientific explanation written afterwards
- Dwhether the direct-current supply is on
42.Use a teacher-approved simulation to compare ion movement when the power supply is switched on and off. Which observation or quantity is the dependent variable?
Easy
- Aion movement and products at each electrode
- Bwhether the direct-current supply is on
- Cthe title given to the investigation
- Dthe number of references in the report
43.Use a teacher-approved simulation to compare ion movement when the power supply is switched on and off. Which decision best controls another factor in this comparison?
Medium
- Achange every condition for each trial
- Bkeep the electrolyte and electrode materials unchanged
- Cuse a different measurement method for every result
- Drecord only results that agree with the prediction
44.Use a teacher-approved simulation to compare ion movement when the power supply is switched on and off. Why should the class repeat measurements or check multiple comparable observations?
Medium
- ATo guarantee that every systematic error disappears
- BTo make an unsupported prediction become correct
- CTo assess variation and judge how consistent the evidence is
- DTo avoid reporting results that disagree with a model
45.A class is evaluating an application of electrolysis and moving ions. Which statement identifies a relevant limitation?
Hard
- AAll scientific models reproduce every feature of the real world
- BOne favourable result proves that a technology has no disadvantages
- CA conclusion needs no evidence when a scientific term is used
- DProducts depend on the electrolyte, water and electrode materials; molten and aqueous electrolytes can give different products.
46.Use a teacher-approved simulation to compare ion movement when the power supply is switched on and off. Which conclusion is most justified by a controlled comparison?
Hard
- AA conclusion restricted to the tested conditions, with uncertainty and limitations stated
- BA claim that the result must hold in all possible conditions
- CA claim that alternative explanations never need testing
- DA claim based only on the most convenient observation
47.Use a teacher-approved simulation to compare ion movement when the power supply is switched on and off. Select the two practices that strengthen the validity of this comparison.
Medium
- Akeep the electrolyte and electrode materials unchanged
- Bchange the measurement method whenever a result is unexpected
- Crecord ion movement and products at each electrode using the same agreed procedure
- Dreport only observations that confirm the prediction
48.When evaluating evidence about electrolysis and moving ions, select the two scientifically defensible statements.
Hard
- AOne result proves the explanation in every situation
- BProducts depend on the electrolyte, water and electrode materials; molten and aqueous electrolytes can give different products.
- CA conclusion should state the conditions and uncertainty of the evidence
- DModels never need revision when new evidence appears
49.Design a fair investigation for this question: Use a teacher-approved simulation to compare ion movement when the power supply is switched on and off. Identify what to compare, what to record and one control.
Medium
50.Explain one use of the science in electrolysis and moving ions and evaluate one limitation of the evidence or application.
Hard
51.In molten lead bromide, which change occurs at the negative electrode?
Hard
- APb2+ loses two electrons to form lead
- BPb2+ gains two electrons to form lead
- CBr- gains electrons to form bromine
- DLead atoms split into protons and electrons
52.Solid and molten ionic compounds contain ions. Why does electrolysis require the melt or a suitable solution?
Hard
- AOnly molten compounds contain any charged particles
- BElectrolysis requires the ions to have no charge
- CIons must move to the electrodes to transfer charge and form products
- DThe positive and negative electrodes must be joined directly

Lernnotizen

## Big idea: electrolysis and moving ions - **Key concept: Systems.** Mobile positive ions move towards the negative cathode and gain electrons. Negative ions move towards the positive anode and lose electrons. - **Related concepts: Models and evidence.** Use a scientific explanation to make predictions, then test it against observations. - **Global context: Scientific and technical innovation.** Electrolysis separates elements from compounds using electrical energy. ## Electrolysis Principles - **Electrolysis** is the breakdown of a molten or aqueous ionic compound by an electric current. - Covalent compounds and solid ionic compounds **cannot** undergo electrolysis because they have no free mobile ions. - **Electrolyte**: molten or dissolved ionic compound that conducts electricity. - **Anode** (positive electrode) attracts **anions** (negative ions). - **Cathode** (negative electrode) attracts **cations** (positive ions). - Use **PANIC**: **P**ositive is **A**node, **N**egative **I**s **C**athode. - Electrons flow from the negative terminal of the power supply to the cathode; they do **not** pass through the electrolyte. - **Reduction** (gain of electrons) occurs at the **cathode**; **oxidation** (loss of electrons) occurs at the **anode**. ## Electrolysis of Molten Compounds - Molten binary ionic compounds decompose into their elements: **metal at cathode**, **non-metal at anode**. - Example: molten PbBr₂ → **Pb** (grey metal) at cathode, **Br₂** (brown gas) at anode. - Ions must be free to move – compound must be **molten** (or in solution). - Electrodes must be **inert** (e.g., graphite or platinum) to avoid side reactions. - Half-equation at cathode: Pb²⁺ + 2e⁻ → Pb. - Half-equation at anode: 2Br⁻ → Br₂ + 2e⁻. ## Electrolysis of Aqueous Sodium Chloride (Brine) - Brine contains Na⁺, Cl⁻, H⁺, OH⁻ ions. - At **cathode**: H⁺ is discharged (less reactive than Na⁺) → **hydrogen gas**. - At **anode**: Cl⁻ is discharged → **chlorine gas**. - Na⁺ and OH⁻ remain in solution → **sodium hydroxide** forms. - Industrial uses: Cl₂ → bleach; H₂ → margarine; NaOH → soap and detergents. ## Electrolysis of Dilute Sulfuric Acid - Contains H⁺, SO₄²⁻, OH⁻ ions. - At **cathode**: H⁺ gains electrons → **hydrogen gas**. - At **anode**: OH⁻ loses electrons → **oxygen gas** (and water). - Volume of H₂ produced is **twice** the volume of O₂. - Gas tests: H₂ – lit splint gives 'squeaky pop'; O₂ – glowing splint relights. ## Electrolysis of Aqueous Solutions - Water dissociates: H₂O ⇌ H⁺ + OH⁻ – these ions compete with solute ions. - At **cathode**: if metal is **less reactive than hydrogen**, metal is deposited; if **more reactive**, hydrogen gas is produced. - At **anode**: if **halide ions** (Cl⁻, Br⁻, I⁻) are present, halogen forms; otherwise **oxygen** from OH⁻. - **Concentration** matters: concentrated halide → halogen; dilute halide → oxygen. - Example: CuSO₄(aq) with graphite electrodes → **Cu** at cathode, **O₂** at anode; blue colour fades. - With copper electrodes: **anode dissolves** (Cu → Cu²⁺ + 2e⁻), **cathode gains mass** (Cu²⁺ + 2e⁻ → Cu); solution concentration remains constant. ## Ionic Half-Equations - **Oxidation Is Loss** (of electrons), **Reduction Is Gain** (OIL RIG). - **REDuction at CAThode** (RED CAT); **ANode for OXidation** (AN OX). - Metal formation: Mⁿ⁺ + n e⁻ → M (reduction). - Hydrogen formation: 2H⁺ + 2e⁻ → H₂. - Halogen formation: 2X⁻ → X₂ + 2e⁻ (oxidation). - Oxygen formation: 4OH⁻ → O₂ + 2H₂O + 4e⁻. - Half-equations must balance atoms and charges. ## Summary Table of Common Electrolyses - Molten PbBr₂: anode – Br₂; cathode – Pb. - Concentrated NaCl(aq): anode – Cl₂; cathode – H₂. - Dilute H₂SO₄: anode – O₂; cathode – H₂. - CuSO₄(aq) (inert electrodes): anode – O₂; cathode – Cu. ## Think like a scientist - Use a teacher-approved simulation to compare ion movement when the power supply is switched on and off. - **Comparison:** whether the direct-current supply is on. **Outcome:** ion movement and products at each electrode. - **Control:** keep the electrolyte and electrode materials unchanged. Explain why this makes the comparison fairer. - **Evidence:** Use a consistent method, repeated observations where appropriate and a table with labelled quantities and units. Keep unexpected results and investigate their cause. - **Safety:** Practical activities need teacher supervision and an appropriate risk assessment. Use the provided data or simulation where the investigation specifies it. - **Inquiry task:** State a testable question, predict the outcome using the science, then explain how your observations would support or challenge the prediction. ## Evaluate the science - Electrolysis separates elements from compounds using electrical energy. - Products depend on the electrolyte, water and electrode materials; molten and aqueous electrolytes can give different products. - **Evaluation task:** Link your conclusion to evidence, identify a limitation and suggest a specific improvement. Distinguish a measured result from an explanation of its cause.

Predicting Products of Aqueous Solutions: Predict the products at the electrodes during electrolysis of aqueous solutions, considering ion discharge based on reactivity and concentration.
Writing Half-Equations for Electrolysis: Write balanced ionic half-equations for reactions at the anode and cathode during electrolysis.
Electrolysis Principles: **Electrolysis** is the breakdown of a molten or aqueous ionic compound by an electric current.
Predicting Products of Molten Compounds: Predict the products at the anode and cathode during electrolysis of molten binary ionic compounds.
Designing scientific inquiries: Plan a fair comparison: Use a teacher-approved simulation to compare ion movement when the power supply is switched on and off.
Evaluating evidence and impacts: Electrolysis separates elements from compounds using electrical energy. Products depend on the electrolyte, water and electrode materials; molten and aqueous electrolytes can give different products.
Electrolysis of Molten Compounds: Molten binary ionic compounds decompose into their elements: **metal at cathode**, **non-metal at anode**.
Electrolysis of Aqueous Sodium Chloride (Brine): Brine contains Na⁺, Cl⁻, H⁺, OH⁻ ions.
Electrolysis of Dilute Sulfuric Acid: Contains H⁺, SO₄²⁻, OH⁻ ions.
Electrolysis of Aqueous Solutions: Water dissociates: H₂O ⇌ H⁺ + OH⁻ – these ions compete with solute ions.
Ionic Half-Equations: **Oxidation Is Loss** (of electrons), **Reduction Is Gain** (OIL RIG).
Summary Table of Common Electrolyses: Molten PbBr₂: anode – Br₂; cathode – Pb.
Electrolysis: **Electrolysis** is the breakdown of a molten or aqueous ionic compound by an electric current.
cannot: Covalent compounds and solid ionic compounds **cannot** undergo electrolysis because they have no free mobile ions.
Electrolyte: **Electrolyte**: molten or dissolved ionic compound that conducts electricity.
Anode: **Anode** (positive electrode) attracts **anions** (negative ions).

Karteikarten

What is the name of the process in which a molten ionic compound is broken down by an electric current?

Electrolysis Electrolysis is defined as the process in which a molten ionic compound is broken down by an electric current.

Which electrode is the positive electrode in an electrolysis cell?

Anode The anode is the positive electrode in an electrolysis cell.

What type of ion is attracted to the cathode?

Cation Cations are positively charged ions and are attracted to the negative cathode.

During electrolysis, what happens at the anode?

Oxidation (loss of electrons) At the anode, negatively charged ions lose electrons, which is oxidation.

In the electrolysis of molten lead(II) bromide, what is produced at the cathode?

Lead Lead ions (Pb²⁺) are attracted to the cathode, gain electrons, and form lead metal.

During the electrolysis of concentrated aqueous sodium chloride (brine), which gas is produced at the anode?

Chlorine Chloride ions (Cl⁻) are discharged at the anode, losing electrons to form chlorine gas.

In the electrolysis of dilute sulfuric acid, what is the volume ratio of hydrogen to oxygen produced?

2:1 Twice as much hydrogen is produced compared to oxygen, so the ratio is 2:1.

Which of the following is a suitable material for inert electrodes?

Graphite Inert electrodes such as graphite or platinum do not participate in side reactions.

In the electrolysis of aqueous copper(II) sulfate with graphite electrodes, what is observed at the anode?

Bubbles of oxygen gas Hydroxide ions (OH⁻) are discharged at the anode, forming oxygen gas and water.

What is the correct balanced half-equation for the formation of hydrogen gas at the cathode during electrolysis?

2H⁺ + 2e⁻ → H₂ Two hydrogen ions gain two electrons to form one hydrogen molecule: 2H⁺ + 2e⁻ → H₂.

In the electrolysis of aqueous sodium chloride, why is hydrogen produced at the cathode instead of sodium?

Sodium is more reactive than hydrogen Hydrogen ions (from water) are less reactive than sodium ions, so they are discharged preferentially.

Which of the following is a use of chlorine produced during the electrolysis of brine?

Making bleach Chlorine is used to make bleach, while hydrogen is used for margarine and sodium hydroxide for soap/detergents.

During the electrolysis of concentrated aqueous sodium chloride (brine), which product is formed at the cathode?

Hydrogen gas In brine, Na⁺ and H⁺ are present. H⁺ is less reactive than Na⁺, so H⁺ is discharged at the cathode, producing hydrogen gas.

A student electrolyses dilute sulfuric acid using platinum electrodes. A gas is collected at the anode that relights a glowing splint. What is this gas?

Oxygen At the anode, OH⁻ ions are discharged to form oxygen gas. Oxygen relights a glowing splint.

Why must lead(II) chloride be molten for electrolysis to occur?

To allow ions to move freely In solid state, ions are fixed in place and cannot move to carry charge. When molten, ions are free to move and conduct electricity.

The half-equation for the formation of oxygen at the anode during electrolysis of dilute sulfuric acid is: 4OH⁻ → O₂ + 2H₂O + 4e⁻. How many electrons are released per molecule of oxygen?

4 The balanced half-equation shows 4OH⁻ lose 4 electrons to form one O₂ molecule. So 4 electrons are released per O₂.

How would you design the inquiry for electrolysis and moving ions?

Use a teacher-approved simulation to compare ion movement when the power supply is switched on and off. Compare whether the direct-current supply is on; record ion movement and products at each electrode; keep the electrolyte and electrode materials unchanged.

What limitation matters when applying electrolysis and moving ions?

Products depend on the electrolyte, water and electrode materials; molten and aqueous electrolytes can give different products.

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