Class 12 chemistry numericals revision: a weekly plan, Dwarka
Numericals in Class 12 chemistry are won by steady practice, not by last-minute cramming.
This post gives parents in Dwarka and Gurugram a four-week plan for solutions, kinetics and electrochemistry, and shows how to check progress at home.
Why these three chapters need a plan
Solutions, chemical kinetics and electrochemistry are the chapters in Class 12 physical chemistry where a student must calculate, not just recall. A child who reads the NCERT text well can still struggle here. A numerical asks for three skills at once: choosing the right formula, putting in the right units, and doing the arithmetic without slips.
Many students leave these chapters for the end. Then they meet all three together, a few weeks before the board exam, and feel they know nothing. Spreading the work out removes that pressure.
The same few problem types repeat in each chapter. Once a student sees the pattern, the numerical stops feeling new. That is the idea behind this plan.
The four-week plan at a glance
This plan assumes the student has already finished the three chapters once in class. If a chapter is still incomplete, finish the theory first. Numericals on half-understood theory only create frustration.
| Week | Chapter | Problem types to practise |
|---|---|---|
| 1 | Solutions | Concentration terms, lowering of vapour pressure, boiling point rise, freezing point fall, osmotic pressure |
| 2 | Electrochemistry | Cell potential, cell potential at other concentrations, conductivity, electrolysis |
| 3 | Chemical kinetics | Rate law, first-order integrated equation, half-life, effect of temperature on rate |
| 4 | All three, mixed | Timed sets, error notebook review, weak types again |
The order is a suggestion. If your child finds kinetics easier, start there to build confidence, and keep the heavier chapter for the second week.
Week 1: solutions
Start with concentration terms: molarity, molality, mole fraction and percentage by mass. Most errors begin here. Molarity uses litres of solution. Molality uses kilograms of solvent. A student who mixes these up will get every later step wrong.
Then move to colligative properties. These are properties that depend on the number of dissolved particles, not on what the particles are. Practise them in this order:
- Relative lowering of vapour pressure when a non-volatile solute is added.
- Rise in boiling point = a constant for the solvent × molality.
- Fall in freezing point = a different constant for the solvent × molality.
- Osmotic pressure = concentration × gas constant × temperature in kelvin.
- The factor i, which compares the number of particles actually present with the number you would expect if nothing split or joined. It is needed when a solute breaks into ions or joins into larger units.
Ask your child one question before every problem: does this solute dissolve as it is, or does it split into ions? That single question decides whether i is needed.
Worked example: boiling point rise. 18 g of glucose (molar mass 180 g/mol) is dissolved in 1 kg of water. Find the rise in boiling point. Take the boiling point constant of water as 0.52 K kg/mol.
- Moles of glucose = 18 ÷ 180 = 0.1 mol.
- Molality = 0.1 mol ÷ 1 kg = 0.1 mol/kg.
- Glucose does not split into ions, so i = 1.
- Rise in boiling point = 0.52 × 0.1 = 0.052 K.
Notice the steps. Mass to moles, moles to molality, check i, then the formula. A student who writes these four lines every time rarely goes wrong.
Week 2: electrochemistry
This chapter has many formulae, so a one-page formula sheet written by the student is useful. The act of writing it also helps memory. Group the formulae under three headings: cells and potential, conductance, and electrolysis.
For cells, practise finding the standard cell potential from two electrode potentials. Then practise the equation that gives the cell potential when concentrations are not 1 mol/L. Many students forget to find the number of electrons transferred, n. Tell your child to write n first, before anything else.
For conductance, learn the link between conductivity, molar conductivity and concentration. Then learn how the molar conductivity of a salt at infinite dilution is built from the values for its separate ions. For electrolysis, the numerical becomes a simple chain: charge from current and time, moles of electrons from charge, moles of product from the half-reaction.
Common slips this week:
- Using the wrong sign for the cathode and anode potentials.
- Mixing minutes and seconds when finding charge.
- Forgetting that conductivity and molar conductivity have different units.
- Leaving out the link between free energy change and cell potential, which also needs n.
Week 3: chemical kinetics
Kinetics is the study of how fast a reaction goes. Begin with the rate law and the order of a reaction, found from data given in a table. Then spend most of the week on first-order reactions, because they are the most common type in the chapter.
For a first-order reaction, the student should know two forms by heart: the integrated equation, k = (2.303 ÷ t) × log([R]0 ÷ [R]), and the half-life, t1/2 = 0.693 ÷ k. The half-life of a first-order reaction does not depend on the starting concentration. Ask your child to say this in their own words.
Worked example: half-life. A first-order reaction has k = 0.0693 min−1. Find its half-life, and the fraction left after two half-lives.
- t1/2 = 0.693 ÷ 0.0693 = 10 min.
- After one half-life, half remains. After two, half of that remains.
- Fraction left = ¼, after 20 minutes.
Finish the week with the equation that links the rate constant to temperature and activation energy. Students often make errors with temperature here. Always convert °C to kelvin first, and check that the gas constant and the energy unit match.
Week 4: mixed practice and the error notebook
Now combine all three chapters. Give timed sets of five or six questions, mixed from different chapters. The mix matters, because in the exam the student must recognise the chapter from the question alone.
Use the error notebook every day. For each wrong answer, the student writes three things: the question number, the exact mistake, and the corrected step. After a few days, a pattern appears. Perhaps it is always the unit of the boiling point constant, or always the sign of an electrode potential. Fixing a pattern is worth more than doing ten fresh questions.
A daily routine that fits a school day
Keep it short and regular. A simple routine for most evenings:
- Five minutes: read the formula sheet for that day's chapter.
- Thirty to forty minutes: solve numericals on paper, writing every step.
- Ten minutes: check answers and update the error notebook.
Writing every step is not optional. Board examiners award marks for steps, and a student who writes them also finds their own mistakes faster. Parents do not need to know the chemistry to help. Check that the notebook is being filled and that a fixed time is kept.
On school days with heavy homework, shorten the practice block but do not skip the day. Ten careful minutes keep the habit alive, and the habit is what makes the plan work.
How a home tutor helps with numericals
Numericals are personal. Two students in the same class may lose marks for completely different reasons: one in unit conversion, the other in choosing the formula. One-to-one home tuition lets the tutor watch the student solve a problem and stop at the exact step where the error happens.
Great Home Tutors offers home tuition only, with no coaching centre and no group batch. You tell us the class, subject, board and your area in Dwarka or Gurugram. A person from our team then calls to understand the student, and the first class is a trial to see the fit before anything is fixed. We also tell you plainly whether a tutor has been verified by us yet.
Key takeaways
- Give solutions, electrochemistry and kinetics one week each, then use week four for mixed sets.
- Practise a little every day and write every step of every numerical.
- Keep an error notebook and fix repeating mistakes in units, signs and formulae.
- Check i, n and the temperature in kelvin before using a formula.
- A tutor can find the exact step where a student goes wrong, but daily practice still has to come from the student.
Frequently asked questions
When should my child start this plan?
Start once the three chapters have been taught at least once in school. The earlier the better, because the four-week cycle can be repeated if the student needs more practice.
How many numericals should be solved in a day?
Quality matters more than count. Solving a few problems carefully, with every step written and checked, is better than rushing through many. Adjust the number to your child's pace.
Is NCERT enough for numericals?
NCERT is the base. Solve all its examples and exercise questions first, and understand each step. Then add extra practice questions from your school or tutor to meet more variations.
My child understands the theory but loses marks in numericals. Why?
This usually points to units, signs or a missed factor such as i or n, not to weak theory. The error notebook will show which one it is.
Can home tuition be arranged for only these chapters?
When you request a tutor, you can add timings and any preference in the "anything else" box on the form. The tutor and family then decide the plan together after the first class.
What to do next. Try it yourself on the page below.
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