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Free Chemistry shorts

रसायन · کیمیا

23 topics, each a handful of cards plus practice questions with explanations. Free to read in full — no sign-up. Counts for TRE-4, STET, BPSC PCS, RRB NTPC, SSC CGL.

23 shorts · 184 practice questions

• Acids, Bases and Salts — pH, Indicators and Everyday Chemicalsअम्ल, क्षार एवं लवण — pH, सूचक और रोज़मर्रा के रसायनThe colour table, the pH numbers and the four salt formulas that general science papers reuse every single cycle.6 CARDS · 8 QUESTIONS
• Carbon and Its Compounds — Three General Formulas, Six Functional Groups and One Naming Ruleकार्बन एवं उसके यौगिक — तीन सामान्य सूत्र, छह क्रियात्मक समूह और एक नामकरण नियमThe whole chapter reduces to three formulas — alkane CnH2n+2, alkene CnH2n, alkyne CnH2n-2 — plus six functional groups and the rule that turns a structure into its IUPAC name. Add the allotropes (diamond does not conduct, graphite does), the 14 u gap between homologues, and why soap fails in hard water, and you have covered every question SSC CGL/CHSL, Railway NTPC/Group D, BPSC TRE-4, CTET and UPSC prelims set on carbon.6 CARDS · 8 QUESTIONS
• Catalysts and the Four Industrial Processes — Haber, Contact, Ostwald and Solvayउत्प्रेरक तथा चार औद्योगिक प्रक्रियाएँ — हैबर, संपर्क, ऑस्टवाल्ड और सॉल्वेA catalyst changes the speed of a reaction without being used up, and never changes the yield. Learn which catalyst belongs to Haber, Contact, Ostwald and Solvay, and most industrial-chemistry questions answer themselves.6 CARDS · 8 QUESTIONS
• Cement, Glass, Ceramics and Fertilisers: Raw Materials, Composition and Usesसीमेंट, काँच, मृत्तिका और उर्वरक: कच्चा माल, संघटन और उपयोगCement is limestone plus clay with gypsum to slow its setting; glass is sand, soda ash and limestone; urea carries the most nitrogen at 46%. Know each material's raw ingredients and one signature fact, and the everyday-chemistry questions in SSC, Railway and TRE-4 turn into easy marks.6 CARDS · 8 QUESTIONS
• Chemical Bonding — Ionic, Covalent, Metallic, and Why Salt Conducts but Sugar Doesn'tरासायनिक आबंधन — आयनिक, सहसंयोजक, धात्विक, और नमक बिजली क्यों चलाता है पर चीनी नहींThe octet rule, transfer versus sharing, why solid salt refuses to conduct while molten salt does, why graphite conducts and diamond doesn't, and the coordinate bond hiding inside the ammonium ion.6 CARDS · 8 QUESTIONS
• Chemical Reactions and Equations — Balancing, the Five Types, Corrosion and Rancidityरासायनिक अभिक्रियाएँ एवं समीकरण — संतुलन, पाँच प्रकार, संक्षारण और विकृतगंधिताEvery chemical equation is balanced for one reason: mass is conserved, so each element must have the same number of atoms on both sides. Learn the five reaction types — combination, decomposition, displacement, double displacement and redox — and the exam questions almost classify themselves. Add corrosion (galvanisation with zinc) and rancidity (nitrogen flushing in chip packets) and you have the whole chapter. Written for SSC CGL/CHSL, Railway NTPC, BPSC TRE-4 Part II, CTET and UPSC Prelims.6 CARDS · 8 QUESTIONS
• Chemistry in Medicine — Analgesics, Antipyretics, Antibiotics, Antiseptics, Disinfectants and Antacidsऔषधियों में रसायन — पीड़ाहारी, ज्वरनाशी, प्रतिजैविक, पूतिरोधी, विसंक्रामी और प्रतिअम्लExams classify drugs by what they do, not by brand. Six classes, a handful of standard examples, and two traps — one drug can sit in several classes, and the same chemical can change class with concentration — cover almost every question on medicinal chemistry.6 CARDS · 8 QUESTIONS
• Concentration of Solutions — Molarity, Molality, Normality, ppm and the Solution-vs-Solvent Trapविलयन की सांद्रता — मोलरता, मोललता, नॉर्मलता, ppm और विलयन बनाम विलायक का जालSix concentration formulas, and almost every wrong answer comes from one mistake: dividing by the solvent when the formula asked for the solution, or the other way round. Learn which denominator each formula wants and the numericals stop failing.6 CARDS · 8 QUESTIONS
• Ethanol and Ethanoic Acid: Sodium Test, Oxidation, Dehydration, Esterification and Saponificationएथेनॉल और एथेनॉइक अम्ल: सोडियम परीक्षण, ऑक्सीकरण, निर्जलीकरण, एस्टरीकरण और साबुनीकरणTwo carbon compounds, five reactions: what ethanol and vinegar's acid do with sodium, carbonates, heat and each other.6 CARDS · 8 QUESTIONS
• Everyday Chemistry — Common Names, Formulas and Uses You Must Recall Instantlyदैनिक जीवन का रसायन — प्रचलित नाम, सूत्र और उपयोग जो तुरंत याद होने चाहिएBaking soda vs washing soda, Plaster of Paris vs gypsum, quick lime vs slaked lime, blue vs green vitriol, methanol vs ethanol — plus the acid in an ant's sting. One-line recall questions worth 1-3 marks in SSC CGL/CHSL, Railway NTPC and Group D, BPSC TRE-4 and CTET science, and every one of them is decided by a single water molecule or a single letter.6 CARDS · 8 QUESTIONS
• Extraction of Metals — Ores, Roasting, Calcination, Smelting and Electrolytic Refiningधातुओं का निष्कर्षण — अयस्क, भर्जन, निस्तापन, प्रगलन और विद्युत-अपघटनी शोधनWhy is aluminium made with electricity while iron is made with coal? The answer is the reactivity series. Follow three real metals — mercury, zinc and aluminium — from rock to pure metal, and roasting, calcination, smelting and electrolytic refining stop being a list of words and become one logical route.6 CARDS · 8 QUESTIONS
• Fossil Fuels: Coal Ranks, Petroleum Fractions, LPG, CNG and the Octane Numberजीवाश्म ईंधन: कोयले की श्रेणियाँ, पेट्रोलियम के अंश, LPG, CNG और ऑक्टेन संख्याPeat → lignite → bituminous → anthracite, the refinery column from LPG to bitumen, LPG vs CNG and what octane 100 means: the fossil-fuel facts science papers keep repeating.6 CARDS · 8 QUESTIONS
• Fuels, Combustion and Flame — Ignition Temperature, Calorific Value and the Three Zonesईंधन, दहन तथा ज्वाला — ज्वलन ताप, ऊष्मीय मान और तीन क्षेत्रThree conditions make a fire, three zones make a flame, and one number ranks every fuel. Learn ignition temperature, the candle's three zones and calorific value, and the whole chapter falls into place — including why water must never be thrown on an oil fire.6 CARDS · 8 QUESTIONS
• Hydrogen, Heavy Water and the Gas Tests — One Formula and One Test for Every Gas Papers Ask Aboutहाइड्रोजन, भारी जल तथा गैसों की पहचान — हर पूछी जाने वाली गैस का एक सूत्र और एक परीक्षणEvery paper hides two or three marks in a single line: which gas turns lime water milky, which blackens lead acetate paper, which formula is heavy water. Learn the formula and the test together and those marks stop being guesswork.6 CARDS · 8 QUESTIONS
• Is Matter Around Us Pure — Elements, Compounds, Mixtures, Colloids and Every Separation Techniqueक्या हमारे आस-पास के पदार्थ शुद्ध हैं — तत्व, यौगिक, मिश्रण, कोलॉइड और पृथक्करण की हर विधिElement, compound, mixture — three boxes, and almost every question here is asking you to put a substance into one of them. Particle size decides the rest: under 1 nm is a solution, 1–100 nm is a colloid, above 100 nm is a suspension, and only the last two scatter light. For separation, name the property being exploited — size, density, immiscibility, sublimation or boiling point — and the technique names itself. Boiling-point gap above 25 K means simple distillation; below it, fractional.6 CARDS · 8 QUESTIONS
• Metals and Non-metals — The Reactivity Series, Extraction and Every Alloy Exams Askधातु एवं अधातु — सक्रियता श्रेणी, निष्कर्षण और परीक्षा में पूछे जाने वाले सभी मिश्रधातुWhy the reactivity series decides everything from displacement to extraction, the roasting-versus-calcination rule, aqua regia, rusting, and the alloy list — brass, bronze, solder, German silver — that SSC, Railway, CTET, UPSC and teacher-recruitment papers reuse.6 CARDS · 8 QUESTIONS
• Polymers, Plastics, Synthetic Fibres, Soaps and Detergents — The Chemistry of Everyday Materialsबहुलक, प्लास्टिक, संश्लेषित रेशे, साबुन और अपमार्जक — रोज़मर्रा की वस्तुओं का रसायनA plastic switch that will not melt, a nylon rope, a soap that fails in hard water — three everyday facts with three exact chemical reasons. This is the highest-frequency chemistry in general awareness papers and needs no equations at all.6 CARDS · 8 QUESTIONS
• Redox, Electrolysis and Cells — Where Electrons Actually Goउपचयन-अपचयन, विद्युत अपघटन और सेल — इलेक्ट्रॉन वास्तव में कहाँ जाते हैंRusting, batteries, electroplating and metal extraction are one idea wearing four costumes: electrons leaving one species and arriving at another. Learn the electron direction and the whole chapter collapses into two rules.6 CARDS · 8 QUESTIONS
• States of Matter — Change of State, Evaporation vs Boiling and the Gas Lawsपदार्थ की अवस्थाएँ — अवस्था परिवर्तन, वाष्पन बनाम क्वथन और गैस नियमThe particle model behind solids, liquids and gases; the six names for changes of state including sublimation and deposition; latent heat of fusion and vaporisation with their standard values; why evaporation cools and boiling does not; Boyle's, Charles's and Gay-Lussac's laws in one line each; plasma and Bose-Einstein condensate — with the trap patterns SSC, Railway NTPC, BPSC TRE-4, CTET and UPSC Prelims set on each.6 CARDS · 8 QUESTIONS
• Structure of the Atom — The Three Particles, the 2n² Rule and Isotopesपरमाणु की संरचना — तीन कण, 2n² नियम और समस्थानिकElectron, proton, neutron — who found each, how Rutherford's gold foil killed the plum-pudding model, the A = Z + N formula, Bohr–Bury's 2n² shell rule, and every isotope exams keep asking about. Written for the general science sections of BPSC TRE-4, CTET, SSC, Railway NTPC and UPSC Prelims.6 CARDS · 8 QUESTIONS
• The Mole Concept — Three Formulas That Convert Grams into Atoms You Cannot Countमोल संकल्पना — तीन सूत्र जो ग्राम को उन परमाणुओं में बदल देते हैं जिन्हें गिना नहीं जा सकताA chemist can weigh grams but cannot count atoms, and the mole is the bridge between the two. Three formulas carry every numerical question in the topic: moles equal given mass divided by molar mass, or particles divided by 6.022 × 10²³, or — for a gas at STP only — volume divided by 22.4 litres. Molar mass in grams per mole is numerically the same as relative molecular mass, which is why CaCO₃ works out to 100 g/mol from 40 plus 12 plus 48. Percentage composition gives the empirical formula; dividing the real molar mass by the empirical one gives the multiplier that turns CH₂O into C₆H₁₂O₆. Two traps repeat: applying 22.4 litres to something that is not a gas, and assuming the number on the packet is one mole.6 CARDS · 8 QUESTIONS
• The Periodic Table — 18 Groups, 7 Periods and Four Trendsआवर्त सारणी — 18 समूह, 7 आवर्त और चार प्रवृत्तियाँMendeleev arranged by atomic mass, Moseley fixed it to atomic number, and everything else follows from where an element sits: radius shrinks across a period, ionisation energy climbs, fluorine wins electronegativity. The table facts SSC, Railway, UPSC and teacher papers ask every cycle.6 CARDS · 8 QUESTIONS
• Valency and Radicals — The Criss-Cross Method That Writes Any Chemical Formulaसंयोजकता एवं मूलक — क्रिस-क्रॉस विधि जो हर रासायनिक सूत्र बना देती हैEvery 'write the formula' question is the same trick on two numbers: swap the valencies as subscripts, then simplify. Once you know calcium is always +2 and phosphate is always -3, calcium phosphate writes itself — Ca3(PO4)2, no memorising required.6 CARDS · 8 QUESTIONS