Chapter section
Board Readiness Diagnostic B - Transfer Check - 20 Marks
Attempt rules
- Time: 22 minutes writing + 5 minutes checking.
- Maximum marks: 20.
- Attempt this only after Diagnostic A.
- Use blank paper and a pen.
- Keep every lesson, revision sheet and answer reveal closed.
- The questions are original board-style practice. They are not predictions or previous-year questions.
Timed paper controller
Diagnostic B transfer attempt
Writing time22:0022 min writing + 5 min checking
Get blank paper and a pen ready. Starting is permanent for this attempt; refreshing does not reset the clock.
Question paper
Section A - Objective questions - 5 marks
- A few drops of dilute sulphuric acid are added before electrolysing water mainly to: (1)
- supply oxygen
- increase electrical conductivity
- change hydrogen into oxygen
- make the water boil
- During electrolysis,
10 cm³oxygen is collected at the anode. The expected volume of hydrogen at the cathode is: (1)
5 cm³10 cm³20 cm³80 cm³
- The cathode:anode mass ratio of gases formed during electrolysis of water is: (1)
2:11:28:11:8
- In
PbO + CO → Pb + CO₂, the reducing agent is: (1)
Final five-minute check
- Did I read volume and mass correctly?
- Did I write ratios in the order asked?
- Did I identify the substance that is oxidised before naming the reducing agent?
- Did I add heat, light or electricity over the arrow?
- Did every observation include a visible colour, gas or temperature change?
🔍 Practice feedback
Answer check
Try first, then reveal the answer
Section A
- Option 2
- Option 3
- Option 4
- Option 2
- Option 3
Section B
- The balanced equation is
2H₂O(l) →[Electricity] 2H₂(g) + O₂(g). It gives two volumes of hydrogen for one volume of oxygen, so cathode:anode volume is2:1. Two moles ofH₂have mass4 g; one mole ofO₂has mass32 g. Therefore, cathode:anode mass is4:32 = 1:8.
CuOloses oxygen and is reduced to copper, soCuOis the oxidising agent. Carbon gains oxygen and is oxidised to carbon dioxide, so carbon is the reducing agent.
Score profile
| Score | Meaning | Next action |
|---|---|---|
| 18-20 | Transfer-ready | Recheck only missed marking points after one day. |
| 14-17 | Nearly ready | Revise the first failed skill and retry with a clean sheet. |
| 9-13 | Familiar examples are not transferring reliably | Revisit Lesson 3 and the redox-agent bridge in Board Exam Practice. |
| 0-8 | Core reasoning needs repair | Return to Lessons 2-5 before repeating either diagnostic. |
Record the first failed skill: conductivity, electrode labels, volume ratio, mass ratio, observation, balancing, reaction condition, or redox agent.
Passing Diagnostic A does not cancel a failure here. A student is ready only when both papers are strong without opening the answers.
⚠️ Common mistake
Common mistakes
- Writing
2:1automatically without checking whether the question asks for mass. - Reversing a ratio when the order changes from cathode:anode to anode:cathode.
- Naming the oxidised substance as the oxidising agent.
- Writing
AgClwhen the question gives silver bromide,AgBr. - Omitting the energy condition from a decomposition equation.
💡 Board tip
Board tips
- Write the requested ratio order beside the working before calculating.
- For agents, use: change → oxidised/reduced → agent.
- In an observation answer, name both the starting colour and final colour.
- Use a new line for every case-based subpart.
⏱️ 1-Minute revision
One-minute revision
- Acid provides ions, so water conducts electricity better.
- Water electrolysis gives
H₂at the cathode andO₂at the anode. - Cathode:anode is
2:1by volume and1:8by mass. - The reducing agent is oxidised; the oxidising agent is reduced.
🎭 Memory strip
Comic recap
Quick scene, quick smile, quick memory. Read this once and the idea sticks better.
Memory strip
Panel 01Priya
I check whether the ratio asks for volume or mass.
Panel 02Rahul
Then I write the electrode order before calculating.
Panel 03Priya
I prove oxidation or reduction before naming an agent.
Panel 04Rahul
And every decomposition equation gets its energy condition.