Lesson note
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)
PbOCOPbCO₂
- Photolytic decomposition is another name for decomposition caused by: (1)
- heat
- pressure
- light
- electricity
Section B - Reasoning questions - 6 marks
- Water gives hydrogen and oxygen in a cathode:anode volume ratio of
2:1, but their mass ratio is1:8. Explain both ratios. (2)
- In
2CuO + C → 2Cu + CO₂, identify the oxidising agent and reducing agent. Explain using oxygen transfer. (2)
- White silver bromide is placed in sunlight. State the observation, name the reaction type and write the balanced equation. (2)
Section C - Observation to equation - 3 marks
- A student strongly heats a white metal nitrate in a boiling tube. Brown fumes are released, a yellow residue remains while hot, and a colourless gas that supports burning is also formed.
(a) Identify the metal nitrate and the brown gas. (1)
(b) Write the balanced equation with the condition. (1)
(c) Name the reaction type. (1)
Section D - Case-based transfer - 6 marks
- A laboratory has three stations:
- Station P passes electricity through acidified water.
- Station Q heats lead(II) oxide with hydrogen:
PbO + H₂ → Pb + H₂O. - Station R places pale-yellow silver bromide in sunlight.
(a) At Station P, why is the water acidified? Name the gases at the cathode and anode. (2)
(b) At Station Q, identify the oxidising agent and reducing agent. Explain each choice using oxygen. (2)
(c) At Station R, state the colour change and write the balanced equation with its condition. (2)
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.
- Pale-yellow silver bromide turns grey because silver forms. It is photochemical or photolytic decomposition:
2AgBr(s) →[Sunlight] 2Ag(s) + Br₂(g)Section C
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 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 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.
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.
End-of-lesson comic recap
Comic recap
Quick scene, quick smile, quick memory. Read this once and the idea sticks better.
4-panel 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.