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CBSE Class 12 · Chemistry

Chemical Kinetics

Official NCERT chapter from Chemistry Part I–II (book code lech1). ExamMaster notes are original teaching at CBSE Class 12 depth.

This lesson follows the official chapter “Chemical Kinetics” in Chemistry Part I–II. The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.

  • CBSE Class 12
  • Medium level
  • 8 concepts

1Rate of a Chemical Reaction

Rate: change of concentration per time as taught. Average versus instantaneous if split. Rate is a speed-of-change, not a K-sit (that was equilibrium). One Δ[ ]/Δt is enough.

A large K as “fast” is the leftover this heading refuses.

Figure. Rate is how fast a concentration changes: −Δ[A]/Δt for a reactant. The curve falling is the story; the chord is the average rate on that interval.

How it works

  1. Name Δconcentration / ΔtimeThe rate.
  2. Keep average or slope as taughtThe sort.
  3. Refuse K as the speedTwo words.

2Factors Influencing Rate of a Reaction

Factors: concentration, T, catalyst, surface as taught. A factor is a knob that moves the rate. One extra T or a named catalyst is enough — not a biography.

A catalyst that moves K as the first claim is a miss (rates both ways).

Figure. For a first-order step, rate = k[A]. Double the concentration and the rate doubles. Temperature and a catalyst change k, not this proportion.

How it works

  1. Name the knobThe factor.
  2. Say the rate changesThe look.
  3. Keep a catalyst off the K-moveHonest.

3Integrated Rate Equations

Integrated rate: first-order ln([ ]0/[ ]) = kt as taught; half-life 0.693/k if named. A straight-line plot picks the order. Integrated is a time-write, not a first-second of the definition.

Using the differential rate as the leftover t-write is a skip.

Figure. The integrated first-order law is a straight line through the origin: −ln([A]/[A]₀) = kt. A curve here means the order is not 1.

How it works

  1. Name the order the lesson is onZero / first / second.
  2. Write the taught integrated formThe equation.
  3. Keep t1/2 as 0.693/k for first-order if askedThe extra.

First-order half-life

k=0.0693 min−1. Find t1/2 (first-order).

  • 0.693/k0.693/0.0693
  • t1/210 min
  • Readtime to half

Pro tip. First-order half-life is 0.693/k.

4Temperature Dependence of the Rate of a Reaction

Temperature: k grows with T as taught; Arrhenius k = A e^{−Ea/RT} if named. A higher Ea is a harder climb. Temperature-look is an energy-gate, not a second concentration-factor.

A lower T as “always faster” is a miss.

Figure. Arrhenius: ln k falls as 1/T rises. The slope is −Ea/R. Hotter (left) means larger k; colder (right) means smaller k.

How it works

  1. Name T and Ea as the knobsThe given.
  2. Read higher T as larger kThe trend.
  3. Keep Arrhenius if taughtHonest extra.

5Collision Theory of Chemical Reactions

Collision theory (school): molecules must meet with enough energy and a taught orientation. Theory is a why-the-rate, not a new integrated form. One meet-and-climb sentence is enough.

Every collision as a reaction is the leftover the energy-gate refuses.

Figure. Only collisions that clear the barrier Ea become product. The peak is that extra energy; products here sit lower than reactants.

How it works

  1. Name meet + enough energy (+ orientation)The theory.
  2. Keep it a whyNot a plot.
  3. Refuse every-bump-as-productThe gate.

6A definition is a test you can run

Rate-word is a test: Δ[ ]/Δt, a factor, an integrated write, Arrhenius, or a collision-gate. If you only say “fast”, you have a heading.

A stopwatch-sticker is not the test.

Figure. A definition you can run: pick two clock times, read [A], compute −Δ[A]/Δt. That number is the average rate on the interval — not a colour word.

How it works

  1. Name the write or the knobThe object.
  2. Give the school sentenceThe test.
  3. Then the word has contentThe definition ran.

7Name the given before the unknown

The given is [ ] and t, or k. The unknown is the rate or t1/2. Copy first-order before you use a second-order write.

Using 0.693/k on a zero-order dump is a silent swap.

Figure. Write the givens first: [A]₀, k, and t. The unknown is [A] after the wait. The law is only a machine for those four names.

How it works

  1. Copy the order and the numbersThe given.
  2. Name k, t, or t1/2The unknown.
  3. Then computeGiven first.

8One worked case is enough at this class

One worked case is enough: t1/2=10 min. Do not stack four plots. The case teaches 0.693/k.

A poster of ten clocks is not more science.

Figure. One case: [A]₀ = 0.80 M, k = 0.20 min⁻¹, t = 5 min. Then [A] = 0.80 e^{−1} = 0.29 M, so [A]/[A]₀ = 1/e ≈ 0.37. That single point sits on the decay.

How it works

  1. Take one first-order kThe case.
  2. Form 0.693/kThe teach.
  3. Stop — one caseThis class.
A large equilibrium K means
  1. Products sit favoured — not “fast”
  2. The rate is huge
  3. t1/2 is zero

K is not a rate.

Notes

  • Mapped to the official NCERT chapter “Chemical Kinetics”. Original teaching only — no textbook sentences.
  • Science here is Physics, Chemistry and Biology ideas at this class, never a language or social-science chapter.

Formulas

  • rate = Δ[ ]/Δt
  • first-order: t1/2=0.693/k
  • k = A e^{−Ea/RT} as taught

Recap

Hold these pegs from the official chapter “Chemical Kinetics”. The wording is ExamMaster’s teaching, not a textbook recap.

Rate of a Chemical Reaction
Rate: change of concentration per time as taught.
Factors Influencing Rate of a Reaction
Factors: concentration, T, catalyst, surface as taught.
Integrated Rate Equations
Integrated rate: first-order ln([ ]0/[ ]) = kt as taught; half-life 0.693/k if named.
Temperature Dependence of the Rate of a Reaction
Temperature: k grows with T as taught; Arrhenius k = A e^{−Ea/RT} if named.
Collision Theory of Chemical Reactions
Collision theory (school): molecules must meet with enough energy and a taught orientation.
A definition is a test you can run
Rate-word is a test: Δ[ ]/Δt, a factor, an integrated write, Arrhenius, or a collision-gate.

Practise Chemical Kinetics

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