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ChemistryClass 10CBSE

Na₂CO₃ Is Also Basic

salt of strong base NaOH + weak acid H₂CO₃; CO₃²⁻ hydrolyses to give OH⁻; pH ≈ 11–12.

ChemistryClass 10CBSE

Is NaHCO₃ basic?

Yes justified:Salt of strong base (NaOH) + weak acid (H₂CO₃)HCO₃⁻ hydrolyses in water → produces OH⁻ ionspH of solution ≈ 8.3–8.5 (mildly alkaline)Turns red litmus blue; reacts with HCl to release CO₂Conversion of NaHCO₃ → Washing Soda:Step 1: 2NaHCO₃ --Heat→ Na₂CO₃ + H₂O + CO₂ (heating) Step 2: Na₂CO₃ + 10H₂O → Na₂CO₃·10H₂O (recrystallisation)

ChemistryClass 10CBSE

Walking on Sand or Ice

On Ice too little friction: The smooth surface cannot provide the backward reaction force (Newton's 3rd Law) needed to push you forward feet slip.On Sand surface gives way: Loose particles shift under foot pressure, absorbing energy without returning a solid reaction force. Each step requires 2–3× more energy than firm ground.Feet hurt on sand because: Calf, arch, and Achilles tendon muscles work 2–3× harder; feet sink and grip sand; constant balance correction strains ankles and knees.Class 9 Core Concept: Walking requires firm ground reaction (Newton's 3rd Law) + adequate friction both are impaired on sand and ice for opposite reasons (too loose vs. too slippery).

GeneralClass 10CBSE

Did Japan ever have wild tigers?

No tigers are not native to Japan. They exist on continental Asia (India, Russia, China, Southeast Asia).

GeneralClass 10CBSE

Which is the national animal of India?

National symbols:SymbolNameYearNational AnimalBengal Tiger1973National BirdIndian Peacock1963National FlowerLotus—National TreeBanyan—National RiverGanga2008National EmblemLion Capital of Ashoka1950National AnthemJana Gana Mana1950National SongVande Mataram1950

ScienceClass 10CBSE

How bleaching powder is made

Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O (Slaked lime + Chlorine gas at ~40°C → Bleaching powder) Uses of bleaching powder:Bleaching agent for cotton, linen, wood pulp (textile & paper industries)Disinfectant for drinking water, swimming pools, sewageKills bacteria by releasing nascent chlorine: CaOCl₂ + H₂O → Ca(OH)₂ + Cl₂Manufacturing chloroform (CHCl₃)Deodoriser for drains and public spaces

GeneralClass 10CBSE

POCSO Act Main Facts

Enacted 2012, amended 2019 (stricter penalties including death penalty)Protects all persons below 18 years of age (not 16 it's 18)Gender-neutral, covers all forms of sexual offencesMandates Special Courts and mandatory reportingFailure to report an offence is itself a crime under this Act

GeneralClass 10CBSE

POCSO vs POSCO

POCSO = Protection of Children from Sexual Offences Act (2012) India's child protection lawPOSCO = POSCO Steel Company (South Korean steel firm) completely unrelated

PhysicsClass 10CBSE

What is are force?

Force is any push or pull that changes or tends to change the state of rest or uniform motion of a body.F = ma (Newton's Second Law) | SI unit: Newton (N) = 1 kg·m/s²Four fundamental forces of nature:GravitationalElectromagneticStrong NuclearWeak NuclearSir Isaac Newton formally defined force in Principia Mathematica (1687).Force in one word: Push or Pull (technically: "Interaction").

ScienceClass 10CBSE

Is milk a type of colloid?

Milk is a liquid-state colloid specifically an oil-in-water emulsion:Dispersed phase: Fat globules (liquid)Dispersion medium: Aqueous solution (water + lactose + proteins)Stabiliser: Casein protein (emulsifier)Shows the Tyndall effect (confirms colloid)

ScienceClass 10CBSE

Is milk matter?

Yes it has mass and occupies space. It is a liquid-state heterogeneous mixture (colloid), not a state of matter itself.

ChemistryClass 10CBSE

What are the 7 fundamental units?

The 7 SI Fundamental (Base) Units:UnitSymbolQuantityMetremLengthKilogramkgMassSecondsTimeAmpereAElectric currentKelvinKTemperatureMolemolAmount of substanceCandelacdLuminous intensityNewton, Joule, and Watt are derived units, not fundamental. Kilogram, metre, and second are the fundamental units most directly used to describe a physical body.

ChemistryClass 10CBSE

What pH is eczema skin?

pH of eczema skin = 5.8 to 7.0 Higher than healthy skin's ideal 4.5–5.5. The disrupted acid mantle weakens the skin barrier.

ChemistryClass 10CBSE

What is pH in water?

pH of pure water = 7.0 at 25°C (equal H⁺ and OH⁻ concentrations of 10⁻⁷ mol/L).

ChemistryClass 10CBSE

What is meant by pH value?

pH scale:pH RangeNatureExample0–below 7AcidicLemon juice (~2), Vinegar (~3)Exactly 7NeutralPure waterAbove 7–14Basic/AlkalineBaking soda (~8), NaOH (~14)

ChemistryClass 10CBSE

What is the full name of pH?

Full name of pH of "Potential of Hydrogen" (from German "Potenz") introduced by S.P.L. Sørensen in 1909.Formula: pH = −log₁₀[H⁺]

ChemistryClass 10CBSE

Is there a 7d orbital?

Yes, theoretically but no currently known element uses it in its ground state.

ChemistryClass 10CBSE

2-8-8-18 rule

Maximum electrons per shell = 2n² (Shell 1 = 2, Shell 2 = 8, Shell 3 = 18, Shell 4 = 32)

ChemistryClass 10CBSE

Three rules governing electron configuration

Aufbau Principle fill lowest energy orbitals firstPauli Exclusion Principle: max 2 electrons per orbital, opposite spinsHund's Rule fill degenerate orbitals singly before pairing

GeneralClass 10CBSE

What information does electron configuration provide?

Distribution of electrons in shells/subshellsNumber of valence electrons → chemical reactivityMagnetic properties (paired = diamagnetic, unpaired = paramagnetic)Element's block, period, and group in the periodic table

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