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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

ChemistryClass 10CBSE

Why is [Ni(en)₃]²⁺ more stable than [Ni(NH₃)₆]²⁺?

Due to the chelate effect:Ethylenediamine (en) is bidentate each en forms a stable 5-membered chelate ring with NiReplacing 6 NH₃ with 3 en molecules releases a net gain of 3 free particles → entropy increases (ΔS > 0)More positive ΔS makes ΔG more negative → greater thermodynamic stabi

ChemistryClass 10CBSE

CFSE of Ni²⁺ (d⁸, octahedral)

Configuration: t₂g⁶ eg² CFSE = 6(−0.4Δₒ) + 2(+0.6Δₒ) = −1.2Δₒ

ChemistryClass 10CBSE

CH3Cl → CH3COOH

CH3Cl + KCN → CH3CN (SN2, chain extended to 2C) → CH3COOH (acid hydrolysis of nitrile).

ChemistryClass 10CBSE

CH3COOCH2CH3 = CH3COOC2H5? 

Both are ethyl acetate. -CH2CH3 and -C2H5 are identical (the ethyl group written in expanded vs. condensed form).

ChemistryClass 10CBSE

CH3OH → C2H5OH (chain extension)

CH3OH → CH3I (using HI) → CH3CN (using KCN) → CH3COOH (hydrolysis) → C2H5OH (reduction with LiAlH₄). Alternatively, use the Grignard route with formaldehyde.

ChemistryClass 10CBSE

CH3CH2NH2 → CH3CH2OH

Diazotisation: React ethylamine with NaNO₂ + HCl at 0–5°C to form the diazonium salt, then hydrolyse with water N₂ gas is released, yielding ethanol.

ChemistryClass 10CBSE

C2H5OH → CH3COOH (Acetic acid)

Oxidation using acidified K₂Cr₂O₇ or KMnO₄ in two stages: Ethanol → Acetaldehyde → Acetic Acid.

ChemistryClass 11CBSE

Why is it incorrect to say that an electron is 'stationary' in an atom?

It is incorrect because electrons are constantly in motion, orbiting or existing in a probability cloud around the nucleus. Their movement is a fundamental aspect of atomic structure and behavior.Electrons are not static. Their continuous motion is responsible for phenomena like chemical bonding and the atom's magnetic properties. Quantum mechanics describes their location as a probability distribution rather than a fixed orbit, but it always implies motion.

ChemistryClass 11CBSE

Imagine you have an unknown element. What single piece of information about its subatomic particles would immediately allow you to identify the element?

The number of protons (or its atomic number) would immediately allow you to identify the element.As stated, the atomic number (number of protons) is unique to each element. Knowing this value is sufficient to identify the element on the periodic table.

ChemistryClass 11CBSE

How does the concept of 'electron shells' or 'energy levels' further refine our understanding of electron 'orbiting'?

Electron shells or energy levels suggest that electrons don't orbit randomly, but occupy specific regions at discrete energy states around the nucleus. This explains the quantized nature of electron energies and how they absorb and emit light.The Bohr model and later quantum mechanical models introduced the idea that electrons exist in specific energy levels or shells. This isn't a simple planetary orbit but a probabilistic distribution of electrons within these defined energy regions, ex

ChemistryClass 11CBSE

What is the primary force that holds the protons and neutrons together within the nucleus, despite the electrostatic repulsion between protons?

The primary force is the strong nuclear force (or strong interaction).Protons, being positively charged, naturally repel each other. The strong nuclear force is an extremely powerful attractive force that acts over very short distances, overcoming this electrostatic repulsion to bind the nucleons (protons and neutrons) together in the nucleus.

ChemistryClass 11CBSE

Explain why the mass number is always a whole number, even though atomic masses often have decimal values.

The mass number represents the count of whole protons and neutrons in a single atom's nucleus, which are discrete particles. Atomic masses, however, are weighted averages of the masses of all naturally occurring isotopes of an element, which often results in decimal values.

ChemistryClass 11CBSE

If an atom has an atomic number of 20 and is electrically neutral, how many protons, neutrons, and electrons could it potentially have (give one possible combination)?

Protons = 20, Electrons = 20. For neutrons, it could vary, for example, 20 neutrons, making the mass number 40.Atomic number 20 means 20 protons. For neutrality, it must have 20 electrons. The number of neutrons can vary, creating isotopes. A common isotope for an element with 20 protons (Calcium) often has 20 neutrons.

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