The steady decrease in the size of lanthanide ions with the increase in atomic number is called lanthanide contraction.
Consequences:
There is not regular trend in ionization potential in the group due to lanthanide contraction.
Similarity of 2nd and 3rd transition group

Applying Nernst equation to the given cell reaction

\({ E }_{ cell }={ { E }^{ ° } }_{ cell }-\frac { 0.0591 }{ n } log\frac { \left[ { Ni }^{ 2+ } \right] }{ { \left[ { Ag }^{ + } \right] }^{ 2 } } =1.05V-\frac { 0.0591 }{ n } log\frac { 0.160 }{ { \left( 0.002 \right) }^{ 2 } } =1.05-\frac { 0.0591 }{ n } log\left( 4\times { 10 }^{ 4 } \right) \)
\(=1.05-\frac { 0.0591 }{ n } (4.6021)=1.05-0.14V\) 
E_(cell) = 0.91 V

The cell can be written as Mg | Mg²⁺(0.130M) |  Ag⁺(0.0001M) | Ag
\(E_{(\text {cell })}=E_{\text {(cell) }}^{\ominus}-\frac{\mathrm{RT}}{2 \mathrm{~F}} \ln \frac{\left[\mathrm{Mg}^{2+}\right]}{\left[\mathrm{Ag}^{+}\right]^{2}}\)
\(=3.17 \mathrm{~V}-\frac{0.059 \mathrm{~V}}{2} \log \frac{0.130}{(0.0001)^{2}}\) 
= 3.17 V – 0.21V = 2.96 V.

\(A_{\mathrm{m}(\mathrm{HAc})}^{\mathrm{o}}=\lambda_{\mathrm{H}^{+}}^{0}+\lambda_{\mathrm{Ac}^{-}}^{0}=\lambda_{\mathrm{H}^{+}}^{0}+\lambda_{\mathrm{Cl}^{-}}^{0}+\lambda_{\mathrm{Ac}^{-}}^{0}+\lambda_{\mathrm{Na}^{+}}^{0}-\lambda_{\mathrm{Cl}^{-}}^{0}-\lambda_{\mathrm{Na}^{+}}^{\mathrm{o}}\)
\(=\Lambda_{m(\mathrm{HCl}}^{0}+A_{m(\mathrm{NaAc})}^{0}-\Lambda_{m(\mathrm{NaCl}}^{\mathrm{o}}\)
= (425.9 + 91.0 – 126.4 ) S cm² mol ^–1
= 390.5 S cm² mol^–1.

i) PhCH₂CH₂COOH 
3-Phenylpropanoic acid               
ii)  (CH₃)₂C = CHCOOH      
3-Methylbut-2-enoic acid
iii) 2-Methylcyclopentane carboxylic acid
iv) 2,4,6-Trinitrobenzoic acid

Silver in its + 1 oxidation state, exhibits 4d¹⁰ 5s^o configuration. But in some compounds, it also shows +2 oxidation state, so the configuration becomes 4d¹⁰ 5s^o. Here, d-orbital is not completely fllled, Therefore, silver is a transition element.

Cr²⁺ is reducing as its configuration changes from d⁴ to d³, the latter having a half-filled t_2g level. On the other hand, the change from Mn³⁺ to Mn²⁺ results in the half-filled (d5) configuration which has extra stability.

The cell will be represented as:
Zn (s) I Zn²⁺(aq) II Ag²⁺ (aq) I Ag (s)
(i) Anode, i.e., zinc electrode will be negatively charged.
(ii) The current will flow from silver to copper in the external circuit.
(iii) At Anode: Zn (s)⇾ Zn2+(aq) + 2 e^-
At Cathode: Ag⁺ (aq) + e ⇾ Ag

We will set up a cell consisting of Mg IMgSO₄ (1M) as one electrode (by dipping a magnesium wire in 1M MgSO₄solution) and standard hydrogen electrode Pt, H₂(1 atm H⁺I (1 M) as the second electrode and measure the EMF of the cell and also note the direction of deflection in the voltmeter. The direction of deflection shows that electrons flow from magnesium electrode to hydrogen electrode, i.e., oxidation takes place on magnesium electrode and reduction on hydrogen electrode. Hence, the cell may be represented as:
\(Mg|{ Mg }^{ 2+ }\left( 1M \right) ||{ H }^{ + }\left( 1M \right) |{ H }_{ 2 },(1 \ atm),Pt\)
\({ { E }^{ ° } }_{ cell }={ { E }^{ ° } }_{ { H }^{ + },1/2{ H }_{ 2 } }-{ { E }^{ ° } }_{ { Mg }^{ 2+ },Mg }\)
\(Put \ { { \ E }^{ ° } }_{ { H }^{ + },1/2{ H }_{ 2 } }=0\)
Hence, E ° Mg²⁺, Mg = - E° cell

(i) In 2,2,6-trimethylcyclohexanone, three methyl groups are present at alpha position with respect to carbonyl group. Hence, the attack of cyanide nucleophile is sterically hindered. In cyclohexanone, there is little steric hinderance. Hence, cyclohexanone forms cyanohydrin in good yield but 2,2,6-trimethylcyclohexanone  does not.
(ii) In senicarbazide, out of two −NH₂ ​ groups, one is involved in resonance with amide carbonyl. The lone pair of electron on N is delocalized through resonance and cannot be donated to a suitable electrophile. Hence, this −NH₂ ​ group cannot act as a nucleophile. Hence, out of two −NH₂ ​ groups in semicarbazide, only one is involved in the formation of semicarbazones.
(iii) During the preparation of esters from a carboxylic acid and an alcohol in the presence of an acid catalyst, the water or the ester should be removed as soon as it is formed. This ensures that the equilibrium will shift in the forward direction and more and more of ester will be formed. Note: The formation of an ester by condensation of carboxylic acid and alcohol is a reversible reaction.

(a)\(4FeCr_2O_4 + 8Na_2CO_3 + 7O_2 \longrightarrow 8Na_2CrO_4 + 2Fe_2O_3 + 8CO_2\)
\(2Na_2CrO_4 + 2H+ \longrightarrow Na_2Cr_2O_7 + 2Na^+ + H_2O\)
\(Na_2Cr_2O_7 + 2KCI \longrightarrow K_2Cr_2O_7 + 2NaCI\)
(b)\(2MnO_2 + 4KOH + O_2 \xrightarrow{\Delta} 2K_2MnO_4 + 2H_2\)
\(\underset{Magnate\ ion}{MnO_4^{2-}}\xrightarrow{electrolysis}\underset{Permagnate\ ion}{MnO_4^-}+e^-\)

(a) E values for Cr³⁺/Cr²⁺is negative (- 0.41 V) and for Mn³⁺/Mn²⁺is positive (+1.57V).Thus, Cr²⁺ can undergo oxidation and, therefore, is reducing agent. On the other hand, Mn(III) can undergo reduction, and therefore, acts as an oxidizing agent.
(b) In the presence of complexing agents, cobalt gets oxidized from,+2 to +3 state because Co (III) is more stable than Co (II).
(c) After the loss of ns electrons, a d1 electron can easily be lost to give a stable configuration. Therefore, the elements having d¹ configuration are either reducing or undergo disproportionation.

Characteristics: 
(i) They show variable oxidation states.
(ii) They form coloured ions
They are called transition elements because they are less electropositive elements because they are less electropositive than p-block elements. Zn, Cd, Hg are not regarded as transition elements.

% of carbon = 69.77 %
% of hydrogen = 11.63 %
% of oxygen = {100 - (69.77 + 11.63)}%
= 18.6 %
Thus, the ratio of the number of carbon, hydrogen, and oxygen atoms in the organic compound can be given as:
\(\mathrm{C}: \mathrm{H}: \mathrm{O}=\frac{69.77}{12}: \frac{11.63}{1}: \frac{18.6}{16}\) 
= 5.81:11.63:1.16
= 5:10:1
Therefore, the empirical formula of the compound is C₅H₁₀O. Now, the empirical formula mass of the compound can be given as:
5 × 12 + 10 ×1 + 1 × 16
= 86
Molecular mass of the compound = 86
Therefore, the molecular formula of the compound is given by C₅H₁₀O.
Since the given compound does not reduce Tollen's reagent, it is not an aldehyde. Again, the compound forms sodium hydrogen sulphate addition products and gives a positive iodoform test. Since the compound is not an aldehyde, it must be a methyl ketone.
The given compound also gives a mixture of ethanoic acid and propanoic acid.
Hence, the given compound is Pentan-2-one.

(i) Acetylation      
Acetyl group is introduced in an organic compound.  Reagent is acetyl chloride or acetic anhydride.
Bases such as pyridine and dimethylaniline are used to neutralize acid (HCl or acetic acid).
(ii) Cannizzaro reaction
Aldehydes (not having alpha hydrogen atoms) undergo self oxidation-reduction (disproportionation) reaction. One molecule is oxidized to carboxylic acid and other molecule is reduced to alcohol. Concentrated alkali is the reagent.
(iii) Cross aldol condensation  
Aldol condensation between different carbonyl compounds (aldehdyes and ketones). If both reactants contain alpha hydrogen atom, four different products can be obtained.
(iv) Decarboxylation
Loss of CO₂​ from carboxylic acids to form hydrocarbons. For this, sodium salts of carboxylic acids are heated with soda lime.

(i)
 
(ii)
 
(iii)
 
(iv)

Conductivity The inverse of resistivity is called conductivity. It is denoted by K (kappa). It is also known as specific conductance. k = 1/p SI unit of conductivity is Sm^-1 or ohm^-1 m^-1
Molar conductivity It is defined as the conductance of the solution which contains one mole of the electrolyte such that entire solution is in between the two electrodes kept one centimeter apart, and large enough to contain all the electrolytes.
Molar conductivity, \(\Lambda _{ m }=\frac { K }{ C } \) 
Variation of conductivity and molar conductivity with concentration.

Conductivity and molar conductivity change with change in concentration of electrolyte ..Conductivity always decreases with decrease in concentration for both weak as well as strong electrolytes.
But molar conductivity increases with decrease in concentration. For strong electrolytes, \(\Lambda _{ m }\) increases slowly with dilution but for weak electrolyte, \(\Lambda _{ m}\) increases steeply on dilution, especially near lower concentrations.

(i) Electronic configurations: In 1^st transition series, 3d orbitals are progressively filled, whereas, in 2nd transition series, 4d orbitals are progressively filled and in 3^rd transition series, 5d-orbitals are progressively filled.
(ii) Oxidation states: Elements show variable oxidation states in both the. series. The highest oxidation state is equal to a total number of electrons in '5' as well as 'd' orbitals. The number of oxidation states shown is less in 5d transition series than 4d series. In 3d series +2, +3 oxidation states are common and they form stable complexes in these oxidation states. In other series, SO₄ and PtF₆ are formed which are quite stable in higher oxidation state. 
(iii) ionization enthalpies: The ionization enthalpy of 5d series is higher than 3d and 4d series due to lanthanide contraction, the effective nuclear charge is more.
(iv) Atomic sizes: The atomic sizes of 4d and 5d series do not differ appreciably due to lanthanoid contraction. The atomic radii of second and third series are larger than 3d series.