Class 12 Chemistry - Chapter The d-and f-Block Elements NCERT Solutions | How would you account for the following:

Explain why Cu⁺ ion is not stable in aqueous solutions?

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

The E^θ(M²⁺/M) value for copper is positive (+0.34V). What is possibly the reason for this? (Hint: consider its high Δ_aHV and low Δ_hydHV)

Actinoid contraction is greater from element to element than lanthanoid contraction. Why?

Which is a stronger reducing agent Cr²⁺ or Fe²⁺ and why?

Explain giving reasons:

(i) Transition metals and many of their compounds show paramagnetic behaviour.

(ii) The enthalpies of atomisation of the transition metals are high.

(iii) The transition metals generally form coloured compounds.

(iv) Transition metals and their many compounds act as good catalyst.

Give examples and suggest reasons for the following features of the transition metal chemistry:

(i)The lowest oxide of transition metal is basic, the highest is amphoteric/acidic.

(ii)A transition metal exhibits highest oxidation state in oxides and fluorides.

(iii) The highest oxidation state is exhibited in oxoanions of a metal.

Predict which of the following will be coloured in aqueous solution?

Ti³⁺, V³⁺, Cu⁺, Sc³⁺, Mn²⁺, Fe³⁺ and Co²⁺.

Give reasons for each.

Describe the preparation of potassium dichromate from iron chromite ore. What is the effect of increasing pH on a solution of potassium dichromate?

How would you account for the irregular variation of ionization enthalpies (first and second) in the first series of the transition elements?

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

Which of the ores mentioned in Table 6.1 can be concentrated by magnetic separation method?

Why are pentahalides more covalent than trihalides?

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

What are micelles? Give an example of a micellers system.

The two strands in DNA are not identical but are complementary. Explain.

Explain the term target molecules or drug targets as used in medicinal chemistry.

Write balanced equations for the following:

(i) NaCl is heated with sulphuric acid in the presence of MnO₂.

(ii) Chlorine gas is passed into a solution of NaI in water.

Discuss the trends in chemical reactivity of group 15 elements.

Aqueous copper sulphate solution (blue in colour) gives:

(i) a green precipitate with aqueous potassium fluoride, and

(ii) a bright green solution with aqueous potassium chloride

Explain these experimental results.

Why does NH₃ form hydrogen bond but PH₃ does not?

How many lattice points are there in one unit cell of each of the following lattice?

(i) Face-centred cubic

(ii) Face-centred tetragonal

(iii) Body-centred

The hexaquo manganese(II) ion contains five unpaired electrons, while the hexacyanoion contains only one unpaired electron. Explain using Crystal Field Theory.

Knowing the electron gain enthalpy values for O → O^- and O → O^2- as -141 and 702 kJ mol^-1 respectively, how can you account for the formation of a large number of oxides having O^2- species and not O^-? (Hint: Consider lattice energy factor in the formation of compounds).