Class 12 Chemistry - Chapter General Principles and Processes of Isolation of Elements NCERT Solutions | Is it true that under certain conditions

What is the significance of leaching in the extraction of aluminium?

Write down the reactions taking place in different zones in the blast furnace during the extraction of iron.

Copper can be extracted by hydrometallurgy but not zinc. Explain.

Outline the principles of refining of metals by the following methods:

(i) Zone refining

(ii) Electrolytic refining

(iii) Vapour phase refining

Name the common elements present in the anode mud in electrolytic refining of copper. Why are they so present ?

The reaction,

      Cr₂O₃  +  2Al    →    Al₂O₃  + 2Cr            (ΔG_o = -421kJ)

is thermodynamically feasible as is apparent from the Gibbs energy value. Why does it not take place at room temperature?

How can you separate alumina from silica in bauxite ore associated with silica? Give equations, if any.

Why is the extraction of copper from pyrites more difficult than that from its oxide ore through reduction?

Write chemical reactions taking place in the extraction of zinc from zinc blende.

Describe a method for refining nickel.

For the reaction R → P, the concentration of a reactant changes from 0.03 M to 0.02 M in 25 minutes. Calculate the average rate of reaction using units of time both in minutes and seconds.

Write the formulas for the following coordination compounds:

(i) Tetraamminediaquacobalt (III) chloride

(ii) Potassium tetracyanonickelate(II)

(iii) Tris(ethane-1,2-diamine) chromium(III) chloride

(iv) Amminebromidochloridonitrito-N-platinate(II)

(v) Dichloridobis(ethane-1,2-diamine)platinum(IV) nitrate

(vi) Iron(III) hexacyanoferrate(II)

(i) Write structures of different isomeric amines corresponding to the molecular formula, C4H11N

(ii) Write IUPAC names of all the isomers.

(iii) What type of isomerism is exhibited by different pairs of amines?

Why are solids rigid?

Write any two characteristics of Chemisorption.

Write the structures of the following compounds.

(i) α-Methoxypropionaldehyde

(ii) 3-Hydroxybutanal

(iii) 2-Hydroxycyclopentane carbaldehyde

(iv) 4-Oxopentanal

(v) Di-sec-butyl ketone

(vi) 4-Fluoroacetophenone

Why are pentahalides more covalent than trihalides?

Silver atom has completely filled d orbitals (4d10) in its ground state. How can you say that it is a transition element?

Glucose or sucrose are soluble in water but cyclohexane or benzene (simple six membered ring compounds) are insoluble in water. Explain.

Write structures of the following compounds:

(i) 2-Chloro-3-methylpentane

(ii) 1-Chloro-4-ethylcyclohexane

(iii) 4-tert. Butyl-3-iodoheptane

(iv) 1,4-Dibromobut-2-ene

(v) 1-Bromo-4-sec. butyl-2-methylbenzene

Arrange the compounds of each set in order of reactivity towards SN2 displacement:

(i) 2-Bromo-2-methylbutane, 1-Bromopentane, 2-Bromopentane

(ii) 1-Bromo-3-methylbutane, 2-Bromo-2-methylbutane, 3-Bromo-2- methylbutane

(iii) 1-Bromobutane, 1-Bromo-2,2-dimethylpropane, 1-Bromo-2-methylbutane, 1-Bromo-3-methylbutane.

Explain on the basis of valence bond theory that [Ni(CN)₄]^2- ion with square planar structure is diamagnetic and the [Ni(CN)₄]^2- ion with tetrahedral geometry is paramagnetic.

Which one of the following has the highest dipole moment?

(i) CH₂Cl₂

(ii) CHCl₃

(iii) CCl₄

When 3-methylbutan-2-ol is treated with HBr, the following reaction takes place:

Give a mechanism for this reaction.

(Hint : The secondary carbocation formed in step II rearranges to a more stable tertiary carbocation by a hydride ion shift from 3rd carbon atom.

Give two reactions that show the acidic nature of phenol. Compare acidity of phenol with that of ethanol.

Classify the following as primary, secondary and tertiary alcohols:

(i)

(ii) CH₂C = CH - CH₂OH 

(iii) CH₃ - CH₂ - CH₂ - OH

(iv)

(v)

(vi)

Specify the oxidation numbers of the metals in the following coordination entities:

(i) [Co(H₂O)(CN)(en)₂]²⁺

(ii) [CoBr₂(en)₂]⁺

(iii) [PtCl₄]^2-

(iv) K₃[Fe(CN)₆]

(v) [Cr(NH₃)₃Cl₃]

Why is  K_a2 <<  K_a1   for H₂SO₄ in water?

Write the equation of the reaction of hydrogen iodide with:

(i) 1-propoxypropane

(ii) Methoxybenzene and

(iii) Benzyl ethyl ether

An organic compound contains 69.77% carbon, 11.63% hydrogen and rest oxygen. The molecular mass of the compound is 86. It does not reduce Tollens' reagent but forms an addition compound with sodium hydrogensulphite and give positive iodoform test. On vigorous oxidation it gives ethanoic and propanoic acid. Write the possible structure of the compound.