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ChemistryClass 10CBSE

What is organic chemistry?

Organic chemistry is the branch of chemistry studying the structure, properties, reactions, and synthesis of carbon-containing compounds.Carbon's unique property of catenation (forming chains, rings, branching structures) creates millions of compounds.Major Areas: Hydrocarbons, functional groups, polymers, proteins, carbohydrates, fats, reaction mechanisms.Why it matters:</

ChemistryClass 10CBSE

What is a buffer solution?

A buffer solution resists changes in pH when small amounts of acid or base are added.Made of a weak acid + its conjugate base (acidic buffer) or weak base + its conjugate acid (basic buffer).Example: Acetic acid + Sodium acetate → acidic buffer (pH ~4.75)How it works:Add acid → conjugate ba

ChemistryClass 10CBSE

What is a solution in chemistry?

A solution is a homogeneous mixture where a solute is uniformly dissolved in a solvent.Particle size less than 1 nmTransparent, does not show Tyndall effectCannot be separated by filtrationTypes:TypeExample</

ChemistryClass 10CBSE

What is a solute?

A solute is the substance dissolved in a solvent to form a solution present in the smaller quantity.SolutionSoluteSolventSalt waterNaClWaterSugar waterSugarWaterCarbonated waterCO₂WaterBrassZincCopper<li data-list-item-id="e0abc399a9

ChemistryClass 10CBSE

What is the Tyndall effect?

The Tyndall effect is the scattering of light by colloidal particles, making the beam path visible. Named after John Tyndall.True solutions: particles too small → no scattering, no visible beam.Colloids: particles large enough → beam visible as a cone of light.Real-life examples:<li data-list-item-id="e1e04fb483daa63eda58a3c2c16

ChemistryClass 10CBSE

What is a colloidal solution?

A colloid has particles of 1–1000 nm scattered through a dispersion medium appearing homogeneous to the naked eye but heterogeneous under a microscope.Particles do not settle.Shows the Tyndall effect.Cannot be separated by filtration.Examples:<figure class="tab

ChemistryClass 10CBSE

What is a suspension in chemistry?

A suspension is a heterogeneous mixture where solid particles larger than 1000 nm are dispersed in a liquid but settle on standing.Opaque, unstable, particles separated by filtration.Does not show Tyndall effect clearly.Examples: Chalk in water, muddy river water, sand in water.A suspension contains large dispersed particles that

ChemistryClass 10CBSE

What is the difference between homogeneous and heterogeneous mixtures?

FeatureHomogeneousHeterogeneousCompositionUniform throughoutNon-uniformPhaseSingle phaseTwo or more phasesComponents visible?NoYesExamplesSalt water, air, alloysSalad, soil, muddy waterHomogeneous mixtures are uniform at all points; heteroge

ChemistryClass 10CBSE

What were the limitations of Mendeleev's periodic table?

Position of hydrogen: Resembles both alkali metals and halogens not correctly placed.Anomalous pairs: Some elements arranged incorrectly (e.g., iodine placed after tellurium despite lower atomic mass).No room for isotopes: Different atomic masses

ChemistryClass 10CBSE

What are transition elements?

Transition elements have partially filled d orbitals in their ground state or in a common oxidation state. They occupy the d-block (Groups 3–12).Characteristic Properties:Variable oxidation statesColoured compounds (d-d electron transitions)Good catalysts (Fe in Haber process, Ni

ChemistryClass 10CBSE

What is lanthanide contraction?

Lanthanide contraction is the gradual decrease in atomic and ionic radii across the lanthanide series (La to Lu), despite increasing atomic number.Electrons added to the inner 4f subshell which are poor shielders of nuclear charge.Effective nuclear charge on outer electrons increases → radius shrinks.Conseque

ChemistryClass 10CBSE

What is ionization enthalpy?

Ionization enthalpy is the enthalpy change when one mole of a gaseous atom loses one electron to form a gaseous cation. Always positive (endothermic).Expressed in kJ/mol.At school level, used interchangeably with ionization energy.Factors affecting it: Nuclear charge, atomic radius, shielding effect, orbital type.Ionization

ChemistryClass 10CBSE

What is ionization energy?

Ionization energy is the minimum energy required to remove the outermost electron from a neutral gaseous atom in its ground state, measured in kJ/mol.Periodic Trend:DirectionTrendReasonAcross a period (left → right)IncreasesNuclear charge increasesDown a groupDecreasesElectrons farther from nucleus</t

ChemistryClass 10CBSE

What is the thermite reaction, and where is it used?

The thermite reaction is a highly exothermic reaction in which aluminium powder reacts with iron oxide to produce molten iron and aluminium oxide at ~3000°C.Equation: 2Al + Fe₂O₃ → Al₂O₃ + 2Fe + HeatApplications:Welding railway tracks molten iron fuses rail gaps (thermite welding)Incendiary applications<li da

ChemistryClass 10CBSE

What is dry ice?

Dry ice is the solid form of carbon dioxide (CO₂) at approximately −78.5°C.Called "dry" because it sublimates directly from solid to gas no liquid state at normal pressure.Uses:Preserving food and biological samples during transportTheatrical fog/smoke effects</

ChemistryClass 10CBSE

What happens when excess carbon dioxide is passed through lime water?

When excess CO₂ is passed through lime water, the initially white precipitate dissolves and the solution clears.Step 1: (Limited CO₂): Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O (lime water turns milky)Step 2: (Excess CO₂): CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂(soluble-solution clears)Excess CO₂ converts insoluble CaCO₃ into soluble Ca(HCO₃)₂, clearing the initially milky lime water.

ChemistryClass 10CBSE

What is rancidity? Mention two methods to prevent it.

Rancidity is the oxidation of fats and oils in food, resulting in bad smell, unpleasant taste, and colour change, making food unfit for consumption.Two Methods to Prevent Rancidity:Antioxidants BHA or Vitamin E is added to inhibit oxidation.Nitrogen flushing packets of chips are filled with nitrogen gas instead of air.Other

ChemistryClass 10CBSE

What is an oxidising agent?

An oxidising agent accepts electrons from another substance, causing that substance to be oxidised, while the oxidising agent itself gets reduced.Memory trick: OIL RIG Oxidation Is Loss, Reduction Is Gain (of electrons).Common Oxidising Agents: O₂, O₃, H₂O₂, KMnO₄, concentrated H₂SO₄ and HNO₃.Example: In 2Mg + O₂ → 2MgO, oxygen is the oxidising agent.An oxidising agent accepts electrons from another substance, causing oxidation of

ChemistryClass 10CBSE

What is a precipitation reaction?

A precipitation reaction occurs when two soluble ionic solutions are mixed and an insoluble solid a precipitate forms.Example: AgNO₃(aq) + NaCl(aq) → AgCl(s)↓ + NaNO₃(aq)Precipitates are identified by colour: AgCl (white), PbS (black), BaSO₄ (white).Used in qualitative analysis to identify ions in solution.

ChemistryClass 10CBSE

What is a neutralisation reaction? Give an example.

A neutralisation reaction occurs when an acid and a base react to produce a salt and water.General Formula: Acid + Base → Salt + WaterAlways exothermic heat is released.Example: HCl + NaOH → NaCl + H₂OApplications: Antacids treat heartburn; lime treats acidic soil; baking soda treats insect stings.A neutralisation reaction between an acid

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