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ChemistryClass 10CBSE

Na-22 vs Na-23

Na-23 is the naturally occurring stable form; Na-22 is a radioactive isotope used in PET scans. For all school chemistry: atomic mass of Na = 23 u.

ChemistryClass 10CBSE

Why sodium's mass is 23

Na has 11 protons + 12 neutrons = 23 u. It has only one stable isotope (Na-23) unlike most elements, no weighted average is needed.

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

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

ChemistryClass 10CBSE

What are the 7 fundamental units?

The 7 SI Fundamental (Base) Units:UnitSymbolQuantityMetremLengthKilogramkgMassSecondsTimeAmpereAElectric currentKelvinKTemperatureMolemolAmount of substanceCandelacd<td

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

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

ChemistryClass 10CBSE

What happens when chuna (lime) is mixed with water?

Chuna (CaO / quicklime) reacts with water to produce bujha hua chuna (slaked lime, Ca(OH)₂) in a highly exothermic reaction. The powder swells, crumbles, and heats dramatically.

ChemistryClass 10CBSE

Is CaO + H₂O → Ca(OH)₂ balanced?

Yes verified:ElementLeftRightCa11O22H22All atoms balance no coefficients needed.

ChemistryClass 10CBSE

When you add water to calcium oxide (CaO)?

A vigorous exothermic reaction occurs, producing calcium hydroxide (slaked lime) with significant heat release:CaO + H₂O → Ca(OH)₂ + Heat This is called "slaking of lime." The mixture heats up, hisses, and steams.

ChemistryClass 10CBSE

What is a Type 2 and Type 4 indicator?

These are not standard classifications in CBSE/ICSE curricula. If a numbered-type system is being used, the likely mapping is:Type 1 = NaturalType 2 = SyntheticType 3 = UniversalType 4 = Olfactory (smell-based, e.g., onion or vanilla change o

ChemistryClass 10CBSE

What are the Big 3 indicators?

IndicatorIn AcidIn NeutralIn BaseLitmusRedPurpleBluePhenolphthaleinColourlessColourlessPinkMethyl OrangeRedOrangeYellow

ChemistryClass 10CBSE

What are the two types of indicators?

Natural Indicators — plant-based (litmus, turmeric, red cabbage juice)Synthetic Indicators — lab-made (phenolphthalein, methyl orange, methyl red)

ChemistryClass 10CBSE

What are the two natural indicators?

Litmus — from lichens; turns red in acid, blue in baseTurmeric — turns reddish-brown in alkaline solutions, stays yellow in acidic or neutral

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