The hydrides of the first elements in groups 15-17, namely NH₃, H₂O and HF respectively show abnormally high values for melting and boiling points. This is due to

• small size of N, O and F

• the ability to form extensive intermolecular H-bonding

• the ability to form extensive intramolecular H-bonding

• effective van der Waals' interaction

The quantity of electricity needed to separately electrolyze 1 M solution of ZnSO₄ , AlCl3 and AgNO₃ completely is in the ratio of

• 2 : 3 :1

• 2 : 1 : 1

• 2 : 1:3

• 2 : 2 : 1

The amount of electrolytes required to coagulate a given amount of Agl colloidal solution (-ve charge) will be in the order

• NaNO₃> Al₂(NO₃)₃ > Ba(NO₃)₂

• Al₂(NO₃)₃ > Ba(NO₃)₂ >NaNO₃

• Al₂(NO₃)₃ > NaNO₃ > Ba(NO₃)₂

•  NaNO₃ > Ba(NO₃)₂ >Al₂(NO₃)₃

Among the following observations, the correct one that differentiates between ${\mathrm{SO}}_3^{2-}$ and ${\mathrm{SO}}_4^{2-}$ is

• both form precipitate with BaCl₂,${\mathrm{SO}}_3^{2-}$ dissolves in HCl but ${\mathrm{SO}}_4^{2-}$ does not.

• ${\mathrm{SO}}_3^{2-}$ forms precipitate with BaCl₂,${\mathrm{SO}}_4^{2-}$ does not.

• ${\mathrm{SO}}_4^{2-}$  forms precipitate with BaCl_2, ${\mathrm{SO}}_3^{2-}$does not

• both form precipitate with BaCl_2, ${\mathrm{SO}}_4^{2-}$ dissolves in HCl but ${\mathrm{SO}}_3^{2-}$ does not.

The two half-cell reactions of an electrochemical cell is given as

$$\begin{gathered} {\mathrm{Ag}}^{+} + {\mathrm{e}}^{-} \to \mathrm{Ag}; \mathrm{E}{°}_{{\mathrm{Ag}}^{+}/\mathrm{Ag}}=-0.3995 \mathrm{V} \\ {\mathrm{Fe}}^{2+}\to {\mathrm{Fe}}^{3+} + {\mathrm{e}}^{-} ; \mathrm{E}{°}_{{\mathrm{Fe}}^{3+} /{\mathrm{Fe}}^{2+}}= -0.7120 \mathrm{V} \end{gathered}$$

The value of cell EMF will be

• -0.3125 V

• 0.3125 V

• 1.114 V

• -1.114V

At 25C, the molar conductance of 0.007 M hydrofluoric acid is 150 mho cm²mol^-1and its $\mathrm{\lambda }{°}_{\mathrm{m}}$ = 500 mho cm²mol^-1. The value of the dissociation constant of the acid at the given concentration at 25°C is

• 7 X 10^-4 M

• 7 X 10^-5 M

• 9 X 10^-3 M

• 9 X 10^-4 M

To observe an elevation of boiling point of 0.05$°$C, the amount of a solute ( mol. wt. = 100) to be added to 100 g of water (K_b= 0.5) is

• 2g

• 0.5g

• 1g

• 0.75g

A piece of wood from an archaeological sample has 5.0 counts min^-1 per gram of C-14, while a fresh sample of wood has a count of 15.0 min^-1g^-1. If half-life of C-14 is 5770 yr, the age of the archaeological sample is

• 8,500 yr

• 9,200 yr

• 10,000 yr

• 11,000 yr

49.

The formal potential of Fe³⁺ /Fe⁴⁺ in a sulphuric acid and phosphoric acid mixture (E° = + 0.61 V) is much lower than the standard potential (E° = + 0. 77 V). This is due to

• formation of the species [FeHPO₄]⁺

• lowering of potential upon complexation

• formation of the species [FeSO₄]⁺

• high acidity of the medium

Cupric compounds are more stable than their cuprous counterparts in solid state. This is because

• the endothermic character of the 2nd IP of Cu is not so high

• size of Cu⁺ is less than Cu²⁺

• Cu²⁺ has stabler electronic configuration as compared to Cu⁺

• the lattice energy released for cupric compounds
  is much higher than Cu⁺