Course

A2 Chemistry: Kinetics and Electrochemistry (9701)

Name: A2 Chemistry: Kinetics and Electrochemistry (9701)
Price: 1499 BDT

Order is measured, never read off an equation, and a feasible reaction may never happen. Rate equations as evidence about mechanism, then electrode potentials as comparisons.

18 lessons1h 50mEnglish

What you'll learn

Write a rate equation from experimental data, and say why the balanced equation cannot supply it
Deduce an order from initial rates by comparing runs that differ in one concentration
Deduce an order from a concentration-time graph, using a constant half-life as the test for first order
Derive the units of a rate constant from the overall order by cancelling
Explain what a zero-order reactant reveals about the position of the rate-determining step
Check a proposed mechanism against both the overall equation and the observed rate equation
Explain homogeneous and heterogeneous catalysis, and why a catalyst leaves ΔH and the equilibrium position alone
Use the Arrhenius equation, in its linear form and in its two-temperature form, to find an activation energy
Explain why no single electrode potential can be measured, and what the hydrogen electrode is for
Calculate a cell potential, identify each electrode, and say why feasible is not the same as fast
Predict whether a redox reaction occurs from the series, and write the balanced ionic equation
Predict the effect of a non-standard concentration on an electrode potential using Le Chatelier
Carry out an electrolysis calculation from current and time through to a mass or a gas volume
Evaluate a hydrogen fuel cell, including where the hydrogen came from

Requirements

AS kinetics: collision theory, activation energy and the Boltzmann distribution
AS redox: oxidation numbers and simple half-equations
AS stoichiometry: the mole, concentration and reacting-mass calculations

Course content

18 lessons · 1h 50m

26.1 · Rate equations

Order is measured, never read off the equation. Two experimental routes to it, and the units of k derived by cancelling rather than recalled.

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Order and the rate equation

The exponents come from experiment, not from the balanced equation. A zero-order reactant is needed and still absent from the rate equation.

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Order from initial rates

Change one concentration at a time and watch what the rate does. Doubling for no change is zero order, for double is first, for quadruple is second.

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Order from a concentration-time graph

A constant half-life is the signature of first order, and it is the only order where the half-life does not depend on where you start.

The rate constant and its units

Substitute mol dm⁻³ and cancel, exactly as for Kc. The units of k tell you the overall order and cost nothing to derive.

26.2 · Mechanism and temperature

A rate equation is evidence about a sequence nobody can watch. Then catalysis, and the equation that connects the rate constant to the activation energy.

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The rate-determining step

Only species up to and including the slow step appear in the rate equation, which makes the rate equation evidence about the mechanism.

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Catalysis

A catalyst provides a different route with a lower activation energy. It changes k, which concentration never does.

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The Arrhenius equation

Why a small rise in temperature makes such a large difference, and how a graph of ln k against 1/T measures the activation energy.

24.2 · Electrode potentials

Every E° is a comparison against the same reference. Combine two, predict a reaction, then ask what changes when the conditions are not standard.

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Standard electrode potential

No single electrode potential can be measured, so every value is against hydrogen, which is zero by definition rather than by measurement.

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Cell potential and feasibility

Subtract the less positive from the more positive. A positive cell potential means the reaction can happen, not that it will happen quickly.

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Predicting reactions from the series

The more positive half-equation runs forwards and the other runs backwards. That single rule replaces memorising a reactivity list.

When conditions are not standard

Change a concentration and apply Le Chatelier to the half-equation. No new equation is needed, and reaching for one is the error.

24.1 · Electrolysis and cells

Force the reaction that would not happen, count the electrons as a reagent, and then look at the devices built on both directions.

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Electrolysis and Faraday's laws

Q = It, divide by F for moles of electrons, then use the half-equation ratio. The AS mole calculation with electrons as the reagent.

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Cells and fuel cells

What a battery is doing while it works and when it is flat, and why a hydrogen fuel cell is only as clean as its hydrogen.

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Kinetics and electrochemistry: exam question

One structured Paper 4 question across orders, the rate-determining step, a cell potential and an electrolysis calculation.

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