Industrial electrolysis and electroplating

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Big idea: industrial electrolysis and electroplating

Key concept: Systems. Metal ions gain electrons at the cathode to form a coating. The electrode arrangement and electrolyte must suit the metal being deposited.
Related concepts: Models and evidence. Use a scientific explanation to make predictions, then test it against observations.
Global context: Scientific and technical innovation. Electroplating improves appearance or resistance to corrosion using a thin metal coating.

What is Electroplating?

Electroplating coats the surface of one metal with a layer of a different metal using electrolysis.
The cathode (negative electrode) is the object to be plated.
The anode (positive electrode) is made of the pure metal that will be plated onto the object.
The electrolyte is an aqueous solution of a soluble salt of the anode metal (e.g., tin(II) chloride for tin plating).
At the anode: metal atoms lose electrons (oxidation) and go into solution as ions.
At the cathode: metal ions gain electrons (reduction) and deposit as metal atoms on the object.
Example half-equations for tin plating: Anode: Sn(s) → Sn²⁺(aq) + 2e⁻; Cathode: Sn²⁺(aq) + 2e⁻ → Sn(s).

Uses of Electroplating

To improve appearance – e.g., silver-plating cutlery and jewellery.
To increase resistance to corrosion – e.g., chromium and nickel plating, galvanising (zinc coating on iron/steel).
To reduce wear or provide a harder surface.

Electroplating Setup

The object to be plated must be very clean and free of grease to ensure good adhesion.
The anode must be the same metal as the plating layer (e.g., silver anode for silver plating).
The electrolyte must contain ions of the plating metal (e.g., silver nitrate for silver plating).
The power supply provides direct current; the object is connected to the negative terminal.

Electroplating a strip of iron with tin

Hydrogen Fuel Cells – Basics

A fuel cell is an electrochemical cell that converts chemical energy from a fuel into electricity.
In a hydrogen-oxygen fuel cell, hydrogen is the fuel and oxygen is the oxidant.
The only product is water; no pollutants are produced.
Overall reaction: 2H₂ + O₂ → 2H₂O (hydrogen + oxygen → water).
At the anode: H₂ → 2H⁺ + 2e⁻ (oxidation of hydrogen).
At the cathode: O₂ + 4H⁺ + 4e⁻ → 2H₂O (reduction of oxygen).
The electrolyte (e.g., potassium hydroxide solution) allows ion flow between electrodes.

Hydrogen-oxygen fuel cell

Advantages of Hydrogen Fuel Cells

No pollutants – only water is produced, unlike petrol engines which emit CO₂, NOₓ, and CO.
High efficiency – more energy per kilogram than petrol or diesel.
Renewable – hydrogen can be produced by electrolysis of water using renewable electricity.

Disadvantages of Hydrogen Fuel Cells

Hydrogen production – most hydrogen currently comes from fossil fuels (releases CO₂); electrolysis requires large amounts of electricity.
Storage and safety – hydrogen is highly flammable and requires high-pressure tanks, making storage difficult and expensive.
Cost and infrastructure – fuel cell materials are expensive; very few hydrogen filling stations exist.

Think like a scientist

Use teacher-provided electroplating data to compare deposited metal masses at different plating times with the same current.
Comparison: the electroplating time. Outcome: the mass of metal deposited.
Control: keep the current and electrolyte composition constant. 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

Electroplating improves appearance or resistance to corrosion using a thin metal coating.
A coating's benefit must be weighed against electrical energy use and the treatment of chemical waste.
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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Câu hỏi luyện tập

Xem trước miễn phí — 8 trên 52 câu hỏi. Đăng ký để xem tất cả.

1.What is electroplating?
Easy
- ACoating the surface of one metal with a layer of a different metal
- BExtracting metals from their ores using electricity
- CBreaking down a compound using heat
- DA method of sacrificial protection
2.In electroplating, the object to be plated is connected to which electrode?
Easy
- AThe negative electrode (cathode)
- BThe positive electrode (anode)
- CThe electrolyte
- DThe power supply
3.What is the product of the reaction in a hydrogen fuel cell?
Easy
- AWater
- BHydrogen peroxide
- COxygen
- DCarbon dioxide
4.Which half-equation represents the reaction at the cathode when electroplating an iron spoon with silver?
Medium
- AAg⁺ + e⁻ → Ag
- BAg → Ag⁺ + e⁻
- CFe²⁺ + 2e⁻ → Fe
- DFe → Fe²⁺ + 2e⁻
5.Which substance is used as the electrolyte when electroplating an iron spoon with copper?
Easy
- AAqueous copper nitrate
- BAqueous iron nitrate
- CCopper rod
- DIron rod
6.In a hydrogen fuel cell, what happens to hydrogen at the anode?
Medium
- AHydrogen is oxidised to form H⁺ ions and electrons
- BHydrogen is reduced to form H⁻ ions
- CHydrogen combines with oxygen to form water
- DHydrogen is produced from water
7.Which of the following is a disadvantage of using hydrogen fuel cells in cars?
Easy
- AHydrogen is difficult to store safely
- BThe only product is water
- CFuel cells are very quiet
- DHydrogen is a renewable fuel
8.Why does the concentration of metal ions in the electrolyte remain constant during electroplating?
Medium
- AMetal ions are removed at the cathode and replenished at the anode at the same rate
- BThe electrolyte is continuously stirred
- CMetal ions are neither produced nor consumed
- DThe power supply is alternating current

Thêm câu hỏi

9.Which of the following is a reason for electroplating an object?
Easy
- ATo improve appearance
- BTo increase its mass
- CTo make it magnetic
- DTo lower its melting point
10.In electroplating, the anode is made from which material?
Easy
- AThe pure metal that will be plated onto the object
- BThe same metal as the object being plated
- CAn inert metal like platinum
- DThe electrolyte solution
11.What is the balanced symbol equation for the overall reaction in a hydrogen fuel cell?
Medium
- A2H₂ + O₂ → 2H₂O
- BH₂ + O₂ → H₂O₂
- C2H₂ + O₂ → 2H₂O₂
- DH₂ + O → H₂O
12.Which of the following statements about electroplating is correct?
Medium
- AThe object to be plated is the cathode
- BThe electrolyte is always a solid
- COxidation occurs at the cathode
- DThe anode is made of the same metal as the object
13.In the electroplating of a steel spoon with silver, the spoon must be very clean and free of grease. What is the most likely reason for this?
Medium
- ATo prevent the silver from reacting with grease
- BTo ensure the silver layer adheres properly to the spoon
- CTo reduce the amount of electricity needed
- DTo avoid contamination of the electrolyte
14.In a hydrogen fuel cell, which substance undergoes oxidation?
Easy
- AOxygen
- BWater
- CHydrogen
- DPotassium hydroxide
15.The overall reaction in a hydrogen fuel cell is 2H2 + O2 → 2H2O. What is the ratio of hydrogen to oxygen consumed in the reaction?
Easy
- A1:1
- B2:1
- C1:2
- D3:1
16.In the electroplating of an iron object with nickel, the electrolyte used is aqueous nickel(II) sulfate. During the process, the concentration of nickel ions in the electrolyte remains constant. Which statement explains this?
Medium
- ANickel ions are reduced at the cathode and oxidised at the anode at equal rates
- BNickel ions are produced at the cathode and used up at the anode
- CThe electrolyte is replenished by adding more nickel sulfate
- DNickel ions do not participate in the reaction
17.A hydrogen fuel cell produces electricity with water as the only product. If methane (CH4) were used as the fuel instead, which additional product would be formed?
Medium
- ACarbon dioxide
- BCarbon monoxide
- CMethanol
- DHydrogen peroxide
18.In a hydrogen fuel cell, the half-equation at the cathode is O2 + 4H+ + 4e− → 2H2O. What is the half-equation at the anode?
Medium
- AH2 → 2H+ + 2e−
- B2H+ + 2e− → H2
- CO2 + 2H2O + 4e− → 4OH−
- D4OH− → O2 + 2H2O + 4e−
19.Which of the following is a disadvantage of using hydrogen fuel cells in vehicles?
Easy
- AThey produce harmful pollutants
- BHydrogen is difficult to store safely
- CThey are less efficient than petrol engines
- DThey require frequent recharging
20.In the electroplating of a steel spoon with silver, the anode is made of silver. What is the purpose of the anode?
Medium
- ATo provide a source of silver ions for the electrolyte
- BTo be plated with silver
- CTo complete the electrical circuit
- DTo reduce silver ions to silver metal
21.A student wants to electroplate an iron rod with copper. Which electrolyte should be used?
Easy
- AAqueous iron(II) sulfate
- BAqueous copper(II) sulfate
- CAqueous silver nitrate
- DPure water
22.In a hydrogen fuel cell, which substance acts as the electrolyte?
Easy
- AHydrogen gas
- BOxygen gas
- CPotassium hydroxide solution
- DWater
23.In a hydrogen fuel cell, hydrogen enters at one electrode and oxygen enters at the other. Which electrode is the anode?
Medium
- AThe electrode where hydrogen enters
- BThe electrode where oxygen enters
- CThe electrolyte
- DThe external circuit
24.In the electroplating of a steel spoon with silver, the spoon is first cleaned and degreased. Which of the following is the most likely reason for this step?
Medium
- ATo ensure good contact between the electrolyte and the spoon so the silver adheres evenly
- BTo ensure the spoon is negatively charged
- CTo increase the conductivity of the spoon
- DTo prevent the silver from reacting with grease
25.A student electroplates an iron rod with nickel. The electrolyte is aqueous nickel(II) sulfate. Which half-equation correctly represents the reaction at the cathode?
Medium
- ANi → Ni2+ + 2e−
- BNi2+ + 2e− → Ni
- CNi + 2e− → Ni2+
- DNi2+ → Ni + 2e−
26.In a hydrogen fuel cell, the half-equation at the anode is H2 → 2H+ + 2e−. Which of the following describes the role of hydrogen in this reaction?
Easy
- AHydrogen is reduced as it gains electrons
- BHydrogen is oxidised as it loses electrons
- CHydrogen acts as the electrolyte
- DHydrogen is the oxidising agent
27.Which of the following is a suitable electrolyte for electroplating an iron spoon with copper?
Easy
- AAqueous iron(II) nitrate
- BAqueous copper(II) nitrate
- CCopper rod
- DIron rod
28.Which of the following materials would NOT be suitable for electroplating?
Easy
- AIron
- BCopper
- CGlass
- DSteel
29.A student sets up an electrolysis cell to electroplate an iron rod with nickel. The iron rod is connected to the positive terminal of the power supply, and a nickel strip is connected to the negative terminal. The electrolyte is aqueous nickel(II) sulfate. What error has the student made?
Medium
- AThe electrolyte should contain iron ions
- BThe iron rod should be connected to the negative terminal
- CBoth electrodes should be made from iron
- DThe circuit should contain a switch
30.In the electroplating of a steel object with copper, the concentration of copper(II) ions in the electrolyte remains constant. Which of the following explains this?
Medium
- ACopper ions are neither produced nor consumed at the electrodes
- BCopper atoms from the anode dissolve to replace copper ions deposited at the cathode
- CThe electrolyte is replenished by adding more copper sulfate crystals
- DCopper ions are recycled by the power supply
31.Complete the sentence:
Easy
In electroplating, the anode is made from the ____ that will be plated onto the object.
32.State the purpose of galvanising.
Easy
33.In a hydrogen fuel cell, the overall reaction is 2H₂ + O₂ → 2H₂O. How many moles of water are produced when 6 moles of hydrogen are consumed?
Medium
34.Complete the sentence about electroplating.
Easy
In electroplating, the object to be plated is connected to the ____ electrode, and the anode is made from the pure ____ that will be plated.
35.A hydrogen fuel cell uses hydrogen and oxygen to produce electricity. Which of the following is a disadvantage of using hydrogen fuel cells in cars?
Easy
- AThe only product is water, which is harmless
- BHydrogen is a renewable fuel
- CHydrogen is difficult to store safely
- DFuel cells produce no noise pollution
36.A student investigates electroplating by coating a copper coin with zinc. The coin is connected to the negative terminal of a power supply, and a zinc electrode is connected to the positive terminal. The electrolyte is aqueous zinc sulfate. After 10 minutes, the coin is removed and weighed. Which of the following would be observed?
Medium
- AThe coin loses mass as copper dissolves
- BThe coin gains mass as zinc is deposited
- CThe zinc electrode gains mass as zinc is deposited
- DThe electrolyte becomes colourless
37.Which of the following is an advantage of using a hydrogen fuel cell compared to a petrol engine?
Easy
- AHydrogen is cheaper than petrol
- BThe only product is water, so no pollutants are produced
- CHydrogen fuel cells are more efficient at low temperatures
- DHydrogen is a liquid at room temperature
38.In an experiment, a student electroplates an iron nail with copper using a copper anode and aqueous copper(II) sulfate as electrolyte. The student uses a variable resistor to control the current. Which of the following changes would increase the mass of copper deposited on the nail in a given time?
Medium
- ADecreasing the current
- BIncreasing the current
- CUsing a larger iron nail
- DUsing a more concentrated electrolyte
39.A student electroplates an iron rod with copper using a copper anode and aqueous copper(II) sulfate. After some time, the concentration of copper(II) ions in the electrolyte is found to be unchanged. Which statement explains this observation?
Medium
- ACopper ions are reduced at the cathode and oxidised at the anode at equal rates
- BCopper ions are not consumed because the electrolyte is a catalyst
- CThe anode dissolves but no copper is deposited on the iron
- DThe iron rod prevents the copper ions from reacting
40.In a hydrogen fuel cell, the overall reaction is 2H2 + O2 → 2H2O. If 4 moles of hydrogen are used, how many moles of oxygen are consumed and how many moles of water are produced?
Medium
- A2 moles of oxygen and 4 moles of water
- B1 mole of oxygen and 2 moles of water
- C4 moles of oxygen and 4 moles of water
- D2 moles of oxygen and 2 moles of water
41.Use teacher-provided electroplating data to compare deposited metal masses at different plating times with the same current. What is the independent variable?
Easy
- Athe mass of metal deposited
- Bthe number of repeated trials
- Cthe electroplating time
- Dthe scientific explanation written afterwards
42.Use teacher-provided electroplating data to compare deposited metal masses at different plating times with the same current. Which observation or quantity is the dependent variable?
Easy
- Athe electroplating time
- Bthe title given to the investigation
- Cthe number of references in the report
- Dthe mass of metal deposited
43.Use teacher-provided electroplating data to compare deposited metal masses at different plating times with the same current. Which decision best controls another factor in this comparison?
Medium
- Akeep the current and electrolyte composition constant
- Bchange every condition for each trial
- Cuse a different measurement method for every result
- Drecord only results that agree with the prediction
44.Use teacher-provided electroplating data to compare deposited metal masses at different plating times with the same current. Why should the class repeat measurements or check multiple comparable observations?
Medium
- ATo guarantee that every systematic error disappears
- BTo assess variation and judge how consistent the evidence is
- CTo make an unsupported prediction become correct
- DTo avoid reporting results that disagree with a model
45.A class is evaluating an application of industrial electrolysis and electroplating. 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 coating's benefit must be weighed against electrical energy use and the treatment of chemical waste.
- DA conclusion needs no evidence when a scientific term is used
46.Use teacher-provided electroplating data to compare deposited metal masses at different plating times with the same current. Which conclusion is most justified by a controlled comparison?
Hard
- AA claim that the result must hold in all possible conditions
- BA claim that alternative explanations never need testing
- CA claim based only on the most convenient observation
- DA conclusion restricted to the tested conditions, with uncertainty and limitations stated
47.Use teacher-provided electroplating data to compare deposited metal masses at different plating times with the same current. Select the two practices that strengthen the validity of this comparison.
Medium
- Akeep the current and electrolyte composition constant
- Bchange the measurement method whenever a result is unexpected
- Crecord the mass of metal deposited using the same agreed procedure
- Dreport only observations that confirm the prediction
48.When evaluating evidence about industrial electrolysis and electroplating, select the two scientifically defensible statements.
Hard
- AOne result proves the explanation in every situation
- BA coating's benefit must be weighed against electrical energy use and the treatment of chemical waste.
- 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 teacher-provided electroplating data to compare deposited metal masses at different plating times with the same current. Identify what to compare, what to record and one control.
Medium
50.Explain one use of the science in industrial electrolysis and electroplating and evaluate one limitation of the evidence or application.
Hard
51.A plating process deposits 0.20 g in 10 min and 0.40 g in 20 min at constant current. Which prediction is most reasonable for 30 min under the same stable conditions?
Hard
- AAbout 0.60 g, subject to checking that the relationship continues
- BExactly 6.0 g regardless of conditions
- C0.20 g because time has no effect
- DNo deposit because the current is constant
52.A manufacturer doubles current and plating time simultaneously and observes more deposited metal. What can the data establish?
Hard
- AOnly time caused the increase
- BThe combined change increases deposition, but it does not isolate either factor's effect
- COnly current caused the increase
- DThe experiment proves there is no energy cost

Ghi chú ôn tập

## Big idea: industrial electrolysis and electroplating - **Key concept: Systems.** Metal ions gain electrons at the cathode to form a coating. The electrode arrangement and electrolyte must suit the metal being deposited. - **Related concepts: Models and evidence.** Use a scientific explanation to make predictions, then test it against observations. - **Global context: Scientific and technical innovation.** Electroplating improves appearance or resistance to corrosion using a thin metal coating. ## What is Electroplating? - **Electroplating** coats the surface of one metal with a layer of a different metal using electrolysis. - The **cathode** (negative electrode) is the object to be plated. - The **anode** (positive electrode) is made of the pure metal that will be plated onto the object. - The **electrolyte** is an aqueous solution of a soluble salt of the anode metal (e.g., tin(II) chloride for tin plating). - At the **anode**: metal atoms lose electrons (oxidation) and go into solution as ions. - At the **cathode**: metal ions gain electrons (reduction) and deposit as metal atoms on the object. - Example half-equations for tin plating: Anode: Sn(s) → Sn²⁺(aq) + 2e⁻; Cathode: Sn²⁺(aq) + 2e⁻ → Sn(s). ## Uses of Electroplating - To **improve appearance** – e.g., silver-plating cutlery and jewellery. - To **increase resistance to corrosion** – e.g., chromium and nickel plating, galvanising (zinc coating on iron/steel). - To **reduce wear** or provide a harder surface. ## Electroplating Setup - The object to be plated must be **very clean and free of grease** to ensure good adhesion. - The **anode** must be the same metal as the plating layer (e.g., silver anode for silver plating). - The **electrolyte** must contain ions of the plating metal (e.g., silver nitrate for silver plating). - The **power supply** provides direct current; the object is connected to the negative terminal. ## Hydrogen Fuel Cells – Basics - A **fuel cell** is an electrochemical cell that converts chemical energy from a fuel into electricity. - In a **hydrogen-oxygen fuel cell**, hydrogen is the fuel and oxygen is the oxidant. - The only product is **water**; no pollutants are produced. - Overall reaction: 2H₂ + O₂ → 2H₂O (hydrogen + oxygen → water). - At the **anode**: H₂ → 2H⁺ + 2e⁻ (oxidation of hydrogen). - At the **cathode**: O₂ + 4H⁺ + 4e⁻ → 2H₂O (reduction of oxygen). - The **electrolyte** (e.g., potassium hydroxide solution) allows ion flow between electrodes. ## Advantages of Hydrogen Fuel Cells - **No pollutants** – only water is produced, unlike petrol engines which emit CO₂, NOₓ, and CO. - **High efficiency** – more energy per kilogram than petrol or diesel. - **Renewable** – hydrogen can be produced by electrolysis of water using renewable electricity. ## Disadvantages of Hydrogen Fuel Cells - **Hydrogen production** – most hydrogen currently comes from fossil fuels (releases CO₂); electrolysis requires large amounts of electricity. - **Storage and safety** – hydrogen is highly flammable and requires high-pressure tanks, making storage difficult and expensive. - **Cost and infrastructure** – fuel cell materials are expensive; very few hydrogen filling stations exist. ## Think like a scientist - Use teacher-provided electroplating data to compare deposited metal masses at different plating times with the same current. - **Comparison:** the electroplating time. **Outcome:** the mass of metal deposited. - **Control:** keep the current and electrolyte composition constant. 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 - Electroplating improves appearance or resistance to corrosion using a thin metal coating. - A coating's benefit must be weighed against electrical energy use and the treatment of chemical waste. - **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.

Evaluating Fuel Cells vs Petrol Engines: Compare advantages and disadvantages of hydrogen fuel cells with petrol engines, focusing on chemical and environmental aspects.
Writing Fuel Cell Half-Equations: Write half-equations for the reactions at the electrodes in a hydrogen-oxygen fuel cell.
Explaining Purposes of Electroplating: State and explain reasons for electroplating, such as corrosion resistance and improved appearance.
Describing Electroplating Setup: Identify the anode, cathode, and electrolyte in an electroplating cell and explain their roles.
Describing Hydrogen Fuel Cell: Describe the structure and operation of a hydrogen-oxygen fuel cell, including the overall reaction.
Writing Electroplating Half-Equations: Write balanced half-equations for the oxidation at the anode and reduction at the cathode during electroplating.
Designing scientific inquiries: Plan a fair comparison: Use teacher-provided electroplating data to compare deposited metal masses at different plating times with the same current.
Evaluating evidence and impacts: Electroplating improves appearance or resistance to corrosion using a thin metal coating. A coating's benefit must be weighed against electrical energy use and the treatment of chemical waste.
What is Electroplating?: **Electroplating** coats the surface of one metal with a layer of a different metal using electrolysis.
Uses of Electroplating: To **improve appearance** – e.g., silver-plating cutlery and jewellery.
Electroplating Setup: The object to be plated must be **very clean and free of grease** to ensure good adhesion.
Hydrogen Fuel Cells – Basics: A **fuel cell** is an electrochemical cell that converts chemical energy from a fuel into electricity.
Advantages of Hydrogen Fuel Cells: **No pollutants** – only water is produced, unlike petrol engines which emit CO₂, NOₓ, and CO.
Disadvantages of Hydrogen Fuel Cells: **Hydrogen production** – most hydrogen currently comes from fossil fuels (releases CO₂); electrolysis requires large amounts of electricity.
Electroplating: **Electroplating** coats the surface of one metal with a layer of a different metal using electrolysis.
cathode: At the **cathode**: O₂ + 4H⁺ + 4e⁻ → 2H₂O (reduction of oxygen).

Thẻ ghi nhớ

What is electroplating?

Coating the surface of one metal with a layer of a different metal Electroplating is defined as coating the surface of one metal with a layer of a different metal. The other options describe extraction, thermal decomposition, and sacrificial protection.

In electroplating, the object to be plated is connected to which electrode?

The negative electrode (cathode) The object to be plated is the cathode (negative electrode) where metal ions gain electrons and deposit as metal atoms.

What is the product of the reaction in a hydrogen fuel cell?

Water The overall reaction in a hydrogen fuel cell is hydrogen + oxygen → water, so water is the only product.

Which half-equation represents the reaction at the cathode when electroplating an iron spoon with silver?

Ag⁺ + e⁻ → Ag At the cathode, reduction occurs: silver ions gain electrons to form silver metal. The correct half-equation is Ag⁺ + e⁻ → Ag.

Which substance is used as the electrolyte when electroplating an iron spoon with copper?

Aqueous copper nitrate The electrolyte must be a soluble salt of the metal being plated (copper), so aqueous copper nitrate is suitable.

In a hydrogen fuel cell, what happens to hydrogen at the anode?

Hydrogen is oxidised to form H⁺ ions and electrons At the anode, hydrogen undergoes oxidation: H₂ → 2H⁺ + 2e⁻. The electrons flow through the external circuit.

Which of the following is a disadvantage of using hydrogen fuel cells in cars?

Hydrogen is difficult to store safely Hydrogen is highly flammable and requires high-pressure tanks for safe storage, which is a disadvantage. The other options are advantages.

Why does the concentration of metal ions in the electrolyte remain constant during electroplating?

Metal ions are removed at the cathode and replenished at the anode at the same rate At the anode, metal atoms lose electrons to form ions (oxidation), replacing the ions that are deposited at the cathode (reduction), so the concentration stays constant.

Which of the following is a reason for electroplating an object?

To improve appearance Electroplating is used to improve appearance and make metals more resistant to corrosion or damage.

In electroplating, the anode is made from which material?

The pure metal that will be plated onto the object The anode is made from the pure metal that will be plated onto the object, so it can supply metal ions to the electrolyte as it oxidises.

What is the balanced symbol equation for the overall reaction in a hydrogen fuel cell?

2H₂ + O₂ → 2H₂O The overall reaction is hydrogen + oxygen → water, balanced as 2H₂ + O₂ → 2H₂O.

Which of the following statements about electroplating is correct?

The object to be plated is the cathode In electroplating, the object to be plated is the cathode (negative electrode) where reduction occurs. Oxidation occurs at the anode.

In the electroplating of a steel spoon with silver, the spoon must be very clean and free of grease. What is the most likely reason for this?

To ensure the silver layer adheres properly to the spoon A clean, grease-free surface allows the silver to deposit evenly and bond strongly to the spoon; grease would prevent adhesion.

In a hydrogen fuel cell, which substance undergoes oxidation?

Hydrogen Hydrogen loses electrons to form H+ ions at the anode; loss of electrons is oxidation. The half-equation is H2 → 2H+ + 2e−.

The overall reaction in a hydrogen fuel cell is 2H2 + O2 → 2H2O. What is the ratio of hydrogen to oxygen consumed in the reaction?

2:1 From the balanced equation, 2 moles of H2 react with 1 mole of O2, so the ratio is 2:1.

In the electroplating of an iron object with nickel, the electrolyte used is aqueous nickel(II) sulfate. During the process, the concentration of nickel ions in the electrolyte remains constant. Which statement explains this?

Nickel ions are reduced at the cathode and oxidised at the anode at equal rates At the anode, nickel metal dissolves to form Ni2+ ions, and at the cathode, Ni2+ ions are deposited as nickel metal. These two processes occur at equal rates, keeping the concentration constant.

How would you design the inquiry for industrial electrolysis and electroplating?

Use teacher-provided electroplating data to compare deposited metal masses at different plating times with the same current. Compare the electroplating time; record the mass of metal deposited; keep the current and electrolyte composition constant.

What limitation matters when applying industrial electrolysis and electroplating?

A coating's benefit must be weighed against electrical energy use and the treatment of chemical waste.

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