Chemical Reactions and Equations rewards pattern recognition more than memorisation — once you can reliably classify a reaction and predict what it produces, balancing the equation is almost mechanical. This is 23 original problems across 5 question types, and every single equation used here has been checked atom-by-atom for correct balance before publishing.
How to use this page: Attempt each problem fully before tapping "Reveal Solution." For classification questions, name the type before checking; for balancing questions, write out your own balanced equation first.
Quick reference — the five reaction types:
| Type | Pattern | Example |
|---|---|---|
| Combination | A + B → AB | 2Mg + O₂ → 2MgO |
| Decomposition | AB → A + B | CaCO₃ → CaO + CO₂ |
| Displacement | A + BC → AC + B | Fe + CuSO₄ → FeSO₄ + Cu |
| Double Displacement | AB + CD → AD + CB | Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl |
| Oxidation-Reduction | Gain/loss of oxygen or hydrogen | CuO + H₂ → Cu + H₂O |
Every Question Type Covered
Balancing chemical equations
Identifying the reaction type
Predicting products & writing equations
Identifying oxidation and reduction
Double displacement & precipitates
Type 1 · Balancing Equations
Balance
Balance the equation: Fe + H₂O → Fe₃O₄ + H₂
Reveal Solution
Balance Fe first, then O, then H
3 Fe atoms and 4 O atoms are needed to match Fe₃O₄
Balance
Balance the equation: Al + O₂ → Al₂O₃
Reveal Solution
O₂ comes in pairs, Al₂O₃ needs 3 oxygens — find the LCM approach
Using 2 Al₂O₃ needs 6 O atoms, so 3 O₂ molecules; then 4 Al atoms needed
Balance
Balance the equation: NaOH + H₂SO₄ → Na₂SO₄ + H₂O
Reveal Solution
Na₂SO₄ needs 2 Na, so use 2 NaOH; this releases 2 H₂O
Balance
Balance the equation: BaCl₂ + Al₂(SO₄)₃ → BaSO₄ + AlCl₃
Reveal Solution
3 sulphate groups need 3 BaCl₂; 2 Al atoms need 2 AlCl₃
Check chlorine: 3 BaCl₂ gives 6 Cl, matching 2 AlCl₃'s 6 Cl
Balance
Balance the equation: Pb(NO₃)₂ → PbO + NO₂ + O₂
Reveal Solution
Start with 2 Pb(NO₃)₂ to get an even number of N and O to balance
Type 2 · Identifying Reaction Type
Classify
CaO + H₂O → Ca(OH)₂ — Identify the type of reaction.
Reveal Solution
Classify
2AgCl --(sunlight)--> 2Ag + Cl₂ — Identify the type of reaction, and its specific sub-type.
Reveal Solution
Classify
Zn + CuSO₄ → ZnSO₄ + Cu — Identify the type of reaction.
Reveal Solution
Classify
Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl — Identify the type of reaction.
Reveal Solution
Classify
2H₂O --(electricity)--> 2H₂ + O₂ — Identify the type of reaction and its specific sub-type.
Reveal Solution
Type 3 · Predicting Products
Predict & Write
Predict the products and write the balanced equation when iron reacts with copper sulphate solution.
Reveal Solution
Iron is more reactive than copper, so it displaces copper
Predict & Write
Predict the products and write the balanced equation when zinc granules react with dilute hydrochloric acid.
Reveal Solution
Predict & Write
Predict the products and write the balanced equation when calcium carbonate is heated strongly.
Reveal Solution
Predict & Write
Predict the products and write the balanced equation when solutions of lead nitrate and potassium iodide are mixed.
Reveal Solution
Predict & Write
Predict the products and write the balanced equation when hydrogen gas is passed over heated copper(II) oxide.
Reveal Solution
Type 4 · Oxidation and Reduction
Identify Oxidised/Reduced
In the reaction CuO + H₂ → Cu + H₂O, identify which substance is oxidised and which is reduced.
Reveal Solution
Check oxygen gain/loss for each reactant
H₂ gains oxygen to become H₂O — this is oxidation. CuO loses oxygen to become Cu — this is reduction.
Identify Oxidised/Reduced
In the reaction ZnO + C → Zn + CO, identify which substance is oxidised and which is reduced.
Reveal Solution
Track oxygen for each substance
Carbon gains oxygen to form CO — oxidation. ZnO loses oxygen to form Zn — reduction.
Real-World Oxidation
Explain, in terms of oxidation, why iron articles develop a reddish-brown coating over time when left exposed.
Reveal Solution
Real-World Oxidation
Why do packaged fatty and oily foods often have nitrogen gas flushed into the packet before sealing?
Reveal Solution
Type 5 · Double Displacement & Precipitates
Identify Precipitate
Silver nitrate solution is mixed with sodium chloride solution. Write the balanced equation and identify the precipitate formed.
Reveal Solution
Identify Precipitate
Sodium carbonate solution is mixed with calcium chloride solution. Write the balanced equation and identify the precipitate.
Reveal Solution
Identify Precipitate
Barium chloride solution reacts with sodium sulphate solution. Write the balanced equation and identify the precipitate.
Reveal Solution
No Precipitate Case
Sodium chloride solution is mixed with potassium nitrate solution. Will a precipitate form? Explain.
Reveal Solution
Classifying, Balancing, and Predicting Are Three Separate Skills
A student who can balance an equation correctly might still misclassify the reaction type, or fail to predict the right products for an unfamiliar reactant pair. A single chapter score doesn't reveal which of these specific gaps exists.
What a Genelis weak area map looks like after working through Chemical Reactions practice
Next session: oxidation-reduction identification (33%) — not more equation balancing. Genelis tracks accuracy by skill, not just by chapter, so it knows exactly which pattern needs more reps.
Genelis is an AI-powered personalized learning platform built on Adaptive Personalized Intelligence. The Genelis learning system generates fresh, unlabelled reaction problems across all 5 types, tracks your accuracy on each specifically, and logs every wrong answer to your wrong-question notebook for reattempt.
Learn smarter. Practice deeper. Improve continuously.
Genelis combines Adaptive Personalized Intelligence, AI-generated notes, targeted practice, mock tests, analytics, and personalised revision to help students improve every study session.
Questions Students Commonly Ask
Quick answers to the most common questions related to this guide.
What are the main types of chemical reactions tested in CBSE Class 10?
Five main types: combination reactions (two or more substances combine to form one product), decomposition reactions (one substance breaks down into two or more, further classified as thermal, electrolytic, or photolytic based on the energy source), displacement reactions (a more reactive element displaces a less reactive one from its compound), double displacement reactions (two compounds exchange ions, often forming a precipitate), and oxidation-reduction reactions (one substance gains oxygen or loses hydrogen while another loses oxygen or gains hydrogen).
How do I identify which reactant is oxidised and which is reduced in a reaction?
At Class 10 level, oxidation is defined as the gain of oxygen or the loss of hydrogen, and reduction is the loss of oxygen or the gain of hydrogen. Look at each reactant individually: if a substance has oxygen added to it or hydrogen removed from it going from reactant to product, it has been oxidised. If a substance loses oxygen or gains hydrogen, it has been reduced. Since oxidation and reduction always happen together, one reactant is oxidised while the other is simultaneously reduced.
How can I tell if a double displacement reaction will form a precipitate?
A precipitate forms when the ions exchanged between the two reactants combine to create a new compound that is insoluble in water. Common examples tested at Class 10 level include barium sulphate (from barium and sulphate ions), lead iodide (bright yellow, from lead and iodide ions), silver chloride (white, from silver and chloride ions), and calcium carbonate. If neither possible new combination of ions is insoluble, no precipitate forms and the reaction is simply an exchange of ions in solution.
What is the difference between thermal, electrolytic, and photolytic decomposition?
All three are decomposition reactions where one compound breaks into two or more products, differing only in the energy source that drives the breakdown. Thermal decomposition uses heat, such as calcium carbonate breaking into calcium oxide and carbon dioxide when heated. Electrolytic decomposition uses electricity, such as water breaking into hydrogen and oxygen gas. Photolytic decomposition uses light, such as silver chloride breaking into silver and chlorine when exposed to sunlight — this is also why silver chloride is used in photographic film.