Chemistry in RRB Group D: What to Study
Chemistry questions in RRB Group D General Science are set at Class 10 NCERT level. The same few areas repeat: common names and formulas of compounds, acids-bases-salts and pH, types of chemical reactions, metals and non-metals, carbon compounds, the periodic table, and the mole concept. Most are one-line facts; a few are short calculations such as molar mass or pH.
Key takeaway: Memorise the 20 common-name formulas and the pH scale below, know which reaction type each NCERT example belongs to, and be able to add atomic masses to get molar mass. That covers most chemistry questions in Group D and NTPC.
Every molar mass and calculation below was computed in Python (atomic masses H 1, C 12, N 14, O 16, Na 23, S 32, Cl 35.5, Ca 40).
RRB Group D Chemistry Important Topics
| Chapter (NCERT Class 9–10) | What is asked most |
|---|---|
| Matter and its states | Sublimation, evaporation, latent heat, diffusion |
| Atoms and molecules | Mole, Avogadro number, molar mass, valency |
| Structure of atom | Protons, neutrons, electrons, isotopes, isobars |
| Chemical reactions and equations | Combination, decomposition, displacement, redox, rusting, rancidity |
| Acids, bases and salts | pH, indicators, common salts and their uses |
| Metals and non-metals | Reactivity series, ores, corrosion, alloys |
| Carbon and its compounds | Covalent bonding, homologous series, functional groups, soaps and detergents |
| Periodic classification | Mendeleev, modern periodic law, groups and periods |
Common Names and Chemical Formulas (Most Asked List)
| Common name | Chemical name | Formula |
|---|---|---|
| Common salt | Sodium chloride | NaCl |
| Baking soda | Sodium hydrogen carbonate | NaHCO₃ |
| Washing soda | Sodium carbonate decahydrate | Na₂CO₃·10H₂O |
| Bleaching powder | Calcium oxychloride (calcium hypochlorite) | CaOCl₂ |
| Plaster of Paris | Calcium sulphate hemihydrate | CaSO₄·½H₂O |
| Gypsum | Calcium sulphate dihydrate | CaSO₄·2H₂O |
| Quicklime | Calcium oxide | CaO |
| Slaked lime | Calcium hydroxide | Ca(OH)₂ |
| Limestone / marble / chalk | Calcium carbonate | CaCO₃ |
| Caustic soda | Sodium hydroxide | NaOH |
| Caustic potash | Potassium hydroxide | KOH |
| Blue vitriol | Copper sulphate pentahydrate | CuSO₄·5H₂O |
| Green vitriol | Ferrous sulphate heptahydrate | FeSO₄·7H₂O |
| Laughing gas | Nitrous oxide | N₂O |
| Dry ice | Solid carbon dioxide | CO₂ |
| Marsh gas | Methane | CH₄ |
| Heavy water | Deuterium oxide | D₂O |
| Oil of vitriol | Sulphuric acid | H₂SO₄ |
| Muriatic acid | Hydrochloric acid | HCl |
| Potash alum | Potassium aluminium sulphate | K₂SO₄·Al₂(SO₄)₃·24H₂O |
Acids, Bases and pH Scale for RRB Group D
| pH | Nature | Everyday example |
|---|---|---|
| Below 7 | Acidic | Lemon juice, vinegar, gastric juice (HCl) |
| 7 | Neutral | Pure water |
| Above 7 | Basic (alkaline) | Baking soda solution, soap solution, milk of magnesia |
| Natural acid | Found in |
|---|---|
| Citric acid | Lemon, orange |
| Acetic acid | Vinegar |
| Lactic acid | Curd, sour milk |
| Tartaric acid | Tamarind, unripe grapes |
| Oxalic acid | Tomato, spinach |
| Formic (methanoic) acid | Ant and nettle sting |
Indicators: litmus turns red in acid and blue in base; phenolphthalein is colourless in acid and pink in base; methyl orange is red in acid and yellow in base.
pH rule: pH = −log[H⁺]. A solution with [H⁺] = 10⁻³ mol/L has pH 3. Each step of 1 in pH is a 10-times change in H⁺ concentration.
Types of Chemical Reactions (NCERT Examples)
| Reaction type | Example |
|---|---|
| Combination | CaO + H₂O → Ca(OH)₂ (quicklime + water, releases heat) |
| Decomposition | CaCO₃ → CaO + CO₂ (on heating) |
| Displacement | Fe + CuSO₄ → FeSO₄ + Cu (iron nail turns brown, solution loses blue colour) |
| Double displacement | Na₂SO₄ + BaCl₂ → BaSO₄ (white precipitate) + 2NaCl |
| Redox | CuO + H₂ → Cu + H₂O (CuO reduced, H₂ oxidised) |
| Neutralisation | NaOH + HCl → NaCl + H₂O |
Corrosion and rancidity: rusting of iron needs both oxygen and water; galvanisation coats iron with zinc. Rancidity is the oxidation of fats and oils, slowed by antioxidants and nitrogen-filled packing.
Metals and Non-Metals Facts for Railway Exams
| Fact | Answer |
|---|---|
| Liquid metal at room temperature | Mercury |
| Liquid non-metal at room temperature | Bromine |
| Best conductor of electricity | Silver (copper is used for wiring because it is cheaper) |
| Non-metal that conducts electricity | Graphite |
| Hardest natural substance | Diamond |
| Metal stored in kerosene | Sodium (and potassium) |
| Non-metal stored in water | White phosphorus |
| Most abundant metal in Earth's crust | Aluminium |
| Brass | Copper + zinc |
| Bronze | Copper + tin |
| Stainless steel | Iron + chromium + nickel (+ carbon) |
| Solder | Lead + tin |
Chemistry Solved Questions for RRB Group D
- Molar mass of water (H₂O)? 2 × 1 + 16 = 18 g/mol.
- Molar mass of calcium carbonate (CaCO₃)? 40 + 12 + 3 × 16 = 100 g/mol.
- Molar mass of sulphuric acid (H₂SO₄)? 2 + 32 + 64 = 98 g/mol.
- How many moles are in 36 g of water? 36 ÷ 18 = 2 mol, that is 2 × 6.022 × 10²³ ≈ 1.2 × 10²⁴ molecules.
- Molar mass of glucose (C₆H₁₂O₆)? 72 + 12 + 96 = 180 g/mol.
- A solution has [H⁺] = 10⁻³ mol/L. Its pH? 3 (acidic).
- Heating limestone gives quicklime and which gas? Carbon dioxide (decomposition reaction).
- Which compound is used to make Plaster of Paris? Gypsum (CaSO₄·2H₂O), heated to about 373 K.
- The chemical formula of baking soda? NaHCO₃.
- Which gas is evolved when zinc reacts with dilute sulphuric acid? Hydrogen (Zn + H₂SO₄ → ZnSO₄ + H₂).
Chemistry Mistakes to Avoid in RRB Group D
- Confusing baking soda (NaHCO₃) with washing soda (Na₂CO₃·10H₂O).
- Mixing quicklime (CaO) and slaked lime (Ca(OH)₂).
- Thinking pH 4 is "a little" more acidic than pH 5: it has 10 times more H⁺.
- Calling brass a copper–tin alloy (that is bronze).
Chemistry for RRB Group D FAQs
What is the level of chemistry in RRB Group D?
Class 10 NCERT level: common names and formulas, acids and bases, reaction types, metals and non-metals, carbon compounds and the periodic table.
How many chemistry questions come in RRB Group D?
General Science has 25 questions in the 100-question CBT, shared between physics, chemistry and biology; chemistry usually accounts for about a third of them.
What is the chemical formula of bleaching powder?
CaOCl₂ (calcium oxychloride), made by passing chlorine over dry slaked lime.
What is the pH of pure water?
7 (neutral) at 25 °C.
Which metal is liquid at room temperature?
Mercury. Bromine is the non-metal that is liquid at room temperature.
Practice Next
- New SSC CGL practice: SSC CGL Science Mock Test 01.
- Mock tests: RRB Group D General Science Chemistry Sectional Mock Test 01, Chemistry Sectional Mock Test 02, RRB Group D General Science Mini Quiz 01, RRB Group D General Science Biology Sectional Mock Test 01 and RRB NTPC CBT 1 Full Mock Test 02.
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