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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 odour in acid/base)

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 stabilityStability constant (log K) for [Ni(en)₃]²⁺ is significantly higher than for [Ni(NH₃)₆]²⁺

ChemistryClass 10CBSE

CFSE of Ni²⁺ (d⁸, octahedral)

Configuration: t₂g⁶ eg² CFSE = 6(−0.4Δₒ) + 2(+0.6Δₒ) = −1.2ΔₒNickel's oxidation states:Most common: +2 (Ni²⁺) — found in NiCl₂, NiSO₄, most coordination complexesAlso known: 0 (Ni(CO)₄), +1 (rare), +3 (NiOOH), +4 (NiO₂)

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 10ICSE

. A metal salt MX when exposed to light splits up to form metal M and a gas X2. Metal M is used in making ornaments whereas gas X2 is used in making bleaching powder. The salt MX is itself used in black and white photography. (a) What do you think metal M is? (b) What could be gas X2? (c) Name the metal salt MX. (d) Name any two salt solutions which on mixing together can produce a precipitate of salt MX. (e) What type of chemical reaction takes place when salt MX is exposed to light? Write the equation of the reaction.

Silver will be metal X Chlorine is the gas evolved when MX salt is exposed to light Silver chloride is the metal salt MX which is used in black and white Silver nitrate and Sodium chloride are the two salt solutions which on mixing together produce a precipitate of salt silver chloride Decomposition reaction is the reaction taking place here when compound decomposes to form simpler new products. Silver chloride decomposes to form silver and chloride gas 2AgCl → 2Ag + Cl2

ChemistryClass 10ICSE

When a strip of red-brown metal X is placed in a colourless salt solution YNO3 then metal Y is set free and a blue coloured salt solution X(NO3)2 is formed. The liberated metal Y forms a shining white deposit on the strip of metal X. (a) What do you think metal X is? (b) Name the salt YNO3. (c) What could be metal Y? (d) Name the salt X(NO3)2 (e) What type of reaction takes place between metal X and salt solution YNO3?

Copper is the metal X which is a red brown strip Silver nitrate is the salt YNO3 which is a colourless salt Silver is the metal formed Y upon reaction of copper and silver nitrate solution thus it forms a shining white deposit on the strip metal X Copper nitrate is X(NO3)2 the salt formed which is blue coloured as copper is present in it Displacement reaction will be the type of reaction taking place here Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2Ag(s)

ChemistryClass 10ICSE

A red-brown metal X forms a salt XSO4. When hydrogen sulphide gas is passed through an aqueous solution of XSO4, then a black precipitate of XS is formed along with sulphuric acid solution. (a) What could the salt XSO4 be? (b) What is the colour of salt XSO4? (c) Name the black precipitate XS. (a) By using the formula of the salt obtained in (a) above, write an equation of the reaction which takes place when hydrogen sulphide gas is passed through its aqueous solution. (e) What type of chemical reaction takes place in this case?

Copper sulphate will be the salt formed named as XSO4 Blue colour is the colour of the salt as it is copper sulphate Copper sulphide is responsible for the black precipitate XS CuSO4 (aq) + H2S (g) → CuS (s) + H2SO4 (aq) Double displacement reaction in which reactant ions exchange places to form new products which results in precipitation reaction.

ChemistryClass 10ICSE

Two metals X and Y form the salts XSO4 and Y2SO4, respectively. The solution of salt XSO4 is blue in colour whereas that of Y2SO4 is colourless. When barium chloride solution is added to XSO4 solution, then a white precipitate Z is formed along with a salt which turns the solution green. And when barium chloride solution is added to Y2SO4 solution, then the same white precipitate Z is formed along with colourless common salt solution. (a) What could the metals X and Y be? (b) Write the name and formula of salt XSO4. (c) Write the name and formula of salt Y2SO4. (d) What is the name and formula of white precipitate Z? Write the name and formula of the salt which turns the solution green in the first case.

Copper is Metal X and Metal Y is Both forms sulphate salts on reaction Copper sulphate, CuSO4is XSO4, the salt formed which is blue in colour Sodium sulphate, Na2SO4 is Y2SO4 which is a colourless salt Barium sulphate, BaSO4 is Z which is a white precipitate formed upon the reaction when barium chloride is added to copper sulphate and turns the solution green Copper chloride, CuCl2 is the salt having yellowish brown colour which turns the solution green

ChemistryClass 10ICSE

A metal X forms a water soluble salt XNO3. When an aqueous solution of XNO3 is added to common salt solution, then a white precipitate of compound Y is formed alongwith sodium nitrate solution. Metal X is said to be the best conductor of electricity and it does not evolve hydrogen when put in dilute hydrochloric acid. (a) What is metal X ? (b) What is salt XNO3? (c) Name the compound Y. (d) Write the chemical equation of the reaction which takes place on reacting XNO3 solution and common salt solution giving the physical states of all the reactants and products. What type of chemical reaction is illustrated by the above equation?

Silver (Ag) will be metal which conducts electricity and does not evolve hydrogen when put in dilute hydrochloric acid Silver nitrate (AgNO3) is XNO3 which is reacts with NaCl (common salt) to give white precipitate Silver chloride (AgCl) is the compound Y formed which is the white precipitate formed from the reaction of silver nitrate and sodium chloride. AgNO3(aq) + NaCl (aq)→ AgCl (s) + NaNO3 (aq) Double displacement reaction where two compounds react and the positive ions and negative ions of the two reactants switch places forming new compounds.

ChemistryClass 10ICSE

When a black metal compound XO is heated with a colourless gas Y2, then metal X and another compound Y2O are formed. Metal X is red-brown in colour which does not react with dilute acids at all. Gas Y2 can be prepared by the action of a dilute acid on any active metal. The compound Y2O is a liquid at room temperature which can turn anhydrous copper sulphate blue. (a) What do you think is metal X? (b) What could be gas Y 2? (c) What is compound XO? (d) What is compound Y2O? (e) Write the chemical equation of the reaction which takes place on heating XO with Y2. What type of chemical reaction is illustrated in the above equation?

Copper (Cu) will be the metal X which is red brown in colour and does not react with dilute acids Hydrogen (H2) is the colourless gas Y2 Copper oxide (CuO) will be the compound XO a black metal compound Water (H2O) is the product formed Y2O CuO + H2 →Cu + H2O Displacement reaction (which is also a redox reaction).Which one active element displaces a less reactive element from its salt solution

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