ACT SSC Chemistry · Unit 3
ACT SSC Chemistry Unit 3: Equilibrium and Redox Reactions — Flashcards & Quiz
ACT SSC Chemistry Unit 3 covers equilibrium and redox reactions within the BSSS framework. This unit explores chemical equilibrium, Le Chatelier’s principle, reaction rates, collision theory, oxidation-reduction reactions and electrochemistry. These flashcards and quiz questions help you revise the key concepts tested in ACT assessments.
Key Terms
- Chemical Equilibrium
- A dynamic state in a reversible reaction where the forward and reverse reaction rates are equal, so concentrations of reactants and products remain constant; a central concept in BSSS Chemistry Unit 3 assessments.
- Le Chatelier's Principle
- When a system at equilibrium is subjected to a change in concentration, temperature or pressure, the system shifts to partially counteract the change; a key qualitative prediction tool in ACT SSC Chemistry.
- Equilibrium Constant (K)
- A numerical value expressing the ratio of product concentrations to reactant concentrations at equilibrium, each raised to their stoichiometric coefficients; calculating K is a core quantitative skill in BSSS assessments.
- Oxidation
- The loss of electrons by a species in a chemical reaction, corresponding to an increase in oxidation state; always occurs simultaneously with reduction in ACT SSC redox problems.
- Reduction
- The gain of electrons by a species in a chemical reaction, corresponding to a decrease in oxidation state; identifying the species being reduced is essential for balancing BSSS half-equations.
- Galvanic Cell
- An electrochemical cell that converts chemical energy into electrical energy through spontaneous redox reactions occurring at two separate electrodes; assessed in ACT SSC Chemistry for cell diagrams and voltage calculations.
- ICE Table
- A systematic method (Initial, Change, Equilibrium) for organising concentration data when solving quantitative equilibrium problems; a standard technique expected in BSSS Chemistry Unit 3 calculations.
Sample Flashcards
Q1: What is a hydrocarbon? Distinguish between saturated and unsaturated hydrocarbons.
A hydrocarbon is a compound containing only carbon and hydrogen. Saturated hydrocarbons (alkanes) have only single C–C bonds. Unsaturated hydrocarbons (alkenes, alkynes) contain at least one C=C double or C≡C triple bond.
Q2: Name the first four alkanes and give their molecular formulae.
Methane (CH₄), ethane (C₂H₆), propane (C₃H₈), butane (C₄H₁₀). Alkanes follow the general formula CₙH₂ₙ₊₂.
Q3: What is a functional group? Name four common functional groups.
A functional group is a specific group of atoms within a molecule that determines its chemical properties and reactions. Common groups: hydroxyl (–OH, alcohols), carboxyl (–COOH, carboxylic acids), amino (–NH₂, amines), carbonyl (C=O, aldehydes/ketones).
Q4: Outline the steps for naming an organic compound using IUPAC rules.
1) Find the longest continuous carbon chain (parent chain). 2) Number from the end nearest the first substituent or functional group. 3) Name and number each substituent. 4) Use prefixes (di-, tri-) for repeated substituents. 5) List substituents alphabetically before the parent name.
Q5: Classify alcohols as primary, secondary or tertiary.
Primary (1°): the carbon bearing –OH is bonded to one other carbon. Secondary (2°): bonded to two other carbons. Tertiary (3°): bonded to three other carbons. Classification affects oxidation behaviour.
Q6: What are structural isomers?
Structural isomers have the same molecular formula but different structural arrangements of atoms (different connectivity). They may have different functional groups, chain lengths or positions of substituents.
Q7: What is geometric (cis-trans) isomerism?
Geometric isomerism occurs in molecules with restricted rotation (e.g. C=C double bonds) where different groups are on the same side (cis) or opposite sides (trans) of the double bond. It requires two different groups on each carbon of the double bond.
Q8: What is an addition reaction? Give an example.
In an addition reaction, atoms or groups are added across a double or triple bond, converting an unsaturated molecule to a more saturated one. No atoms are lost.
Sample Quiz Questions
Q1: Alkenes are saturated hydrocarbons.
Answer: FALSE
Alkenes are UNSATURATED — they contain at least one C=C double bond. Alkanes are saturated.
Q2: The general formula for alkanes is CₙH₂ₙ₊₂.
Answer: TRUE
Alkanes follow CₙH₂ₙ₊₂: methane CH₄, ethane C₂H₆, propane C₃H₈.
Q3: The hydroxyl group (–OH) is characteristic of carboxylic acids.
Answer: FALSE
The hydroxyl group (–OH) is characteristic of alcohols. Carboxylic acids have the carboxyl group (–COOH).
Q4: In IUPAC naming, the parent chain is the longest continuous carbon chain.
Answer: TRUE
The parent chain determines the base name. Substituents are named as prefixes.
Q5: Structural isomers have the same molecular formula and the same structural formula.
Answer: FALSE
Structural isomers have the same molecular formula but DIFFERENT structural formulae (different connectivity).
Why It Matters
Equilibrium and redox reactions in ACT SSC Chemistry Unit 3 connects reaction kinetics with the concepts of dynamic balance and electron transfer. BSSS assessments require you to write equilibrium expressions, apply Le Chatelier’s principle, perform ICE table calculations, assign oxidation states, and balance redox half-equations. This unit develops both qualitative reasoning about how chemical systems respond to change and quantitative skills in equilibrium and redox analysis. Students who master the systematic approach to equilibrium calculations and redox balancing build the analytical foundation essential for the more applied chemistry in Unit 4. Equilibrium concepts connect to the structure and design unit, where Le Chatelier's principle guides industrial process optimisation, and redox half-equations underpin electrochemical cell analysis. BSSS exam questions on equilibrium and redox commonly require you to set up ICE tables or balance half-equations under timed conditions, so practise both methods until you can complete them accurately within two minutes each.
Key Concepts
Reaction Rates and Collision Theory
Collision theory explains how temperature, concentration, surface area, and catalysts affect the rate of chemical reactions. Understanding activation energy, energy profile diagrams, and the role of catalysts provides the kinetic foundation for understanding why reactions reach equilibrium.
Chemical Equilibrium
At equilibrium, forward and reverse reactions continue at equal rates with constant macroscopic properties. Writing equilibrium expressions, calculating Kc from concentration data, using ICE tables, and interpreting the magnitude of K are essential quantitative skills for BSSS assessments.
Le Chatelier’s Principle and Acids/Bases
Systems at equilibrium shift to partially counteract imposed changes. Predicting the direction and extent of shift for changes in concentration, temperature and pressure, and applying equilibrium concepts to acid-base chemistry, are the most frequently tested qualitative skills.
Oxidation-Reduction Reactions
Redox reactions involve the transfer of electrons between species. Assigning oxidation states, writing and balancing half-equations, and identifying oxidising and reducing agents are systematic skills that underpin the electrochemistry studied in Unit 4.
Common Mistakes to Avoid
- Stating that equilibrium means the reaction has stopped — BSSS examiners penalise this misconception; at equilibrium both forward and reverse reactions continue at equal rates, making it a dynamic state.
- Applying Le Chatelier's principle to a catalyst — adding a catalyst does not shift the equilibrium position; it only increases the rate at which equilibrium is reached, which is a common ACT SSC exam trap.
- Confusing oxidation with reduction by forgetting the mnemonic OIL RIG — in BSSS half-equation balancing, always verify that Oxidation Is Loss of electrons and Reduction Is Gain of electrons.
- Writing equilibrium expressions that include solids or pure liquids — ACT Board of Senior Secondary Studies marking guides require only aqueous and gaseous species in the equilibrium constant expression.
- Forgetting to balance both mass and charge in redox half-equations — BSSS assessments require that atoms and net charge are balanced on both sides of each half-equation.
Study Tips
- Practise ICE table calculations regularly, beginning with straightforward equilibrium problems and advancing to those involving quadratic solutions.
- Build flashcards for Le Chatelier’s responses to each type of disturbance and for oxidation state rules, reviewing with spaced repetition.
- Always write the balanced equation and equilibrium expression before attempting any equilibrium problem to prevent stoichiometric errors.
- Drill oxidation state assignments and half-equation balancing with diverse compounds until the process becomes automatic.
- Link equilibrium and redox concepts to industrial examples like the Haber process and electrochemical cells to practise applying theory to real contexts.
- Before your exam, work through the practice questions in this set at least twice using spaced repetition. Testing yourself repeatedly is the most effective revision strategy for long-term retention.
Related Topics
Frequently Asked Questions
What does ACT SSC Chemistry Unit 3 cover?
Unit 3 covers chemical equilibrium, Le Chatelier’s principle, reaction rates, collision theory, acids and bases, oxidation-reduction reactions and electrochemistry fundamentals.
How many flashcards are in this set?
This free set contains 20 flashcards and 20 true/false quiz questions covering all key concepts in Unit 3, aligned to the BSSS Chemistry framework.
Are these flashcards aligned to the ACT curriculum?
Yes — every flashcard and quiz question is mapped to the BSSS Science Framework for ACT SSC Chemistry Unit 3.
Last updated: March 2026 · 20 flashcards · 20 quiz questions · Content aligned to the BSSS Framework