Chemistry:2015: CBSE: [Delhi]:Set -II

For S_N2 reactions the rate of reaction is faster for primary alkyl halides as compared to tertiary alkyl halides because of less steric hindrance experienced by the approaching nucleophile. Hence, out of the given pair (CH₃−CH₂−Br) would undergo S_N2 reaction faster.

According to the Hardy–Schulze rule, the greater the charge of a coagulating ion, the greater is its power to cause precipitation of the oppositely charged ion. Between Ba²⁺ (from BaCl₂) and K⁺ (from KCl), Ba²⁺ has greater charge. Therefore, it will be more effective in causing the coagulation of a negatively charged colloidal sol.

Basicity of oxoacid of Phosphorus = Total no. of P–OH bonds
Hence, its basicity is 3.

2,5-Dinitrophenol

i. Sodium borohydride (NaBH₄)

ii. Alkaline potassium permanganate (KMnO₄-KOH)

The non ideal solutions having vapour pressure higher than the solution exhibit positive deviation from Raoult’s law. In case of positive deviation from Raoult’s law, the intermolecular attractive forces between the solute-solvent molecules are weaker than those between the solute-solute and solvent-solvent molecules.

Heat is absorbed during the formation of such solutions and Δ_mixH has a positive sign. Volume of the solution formed is more, i.e. D_mixV > 0

A mixture of ethanol and acetone is an example of a solution that shows a positive deviation from Raoult’s law.

Azeotropes are the binary mixtures of solutions that have the same composition in liquid and vapour phases and boil at constant temperature. It is not possible to separate their components by fractional distillation.

A minimum-boiling azeotrope is formed by solutions showing a positive deviation from Raoult’s law at a specific composition. Example: An ethanol–water mixture containing approximately 95% ethanol by volume.

a) Given:

The relationship between the standard free energy change and EMF of a cell reaction is given by
ΔG°=−nFE°

Thus, the more positive the standard reduction potential of a reaction, the more negative is the standard free energy change associated with the process and consequently, the higher is the feasibility of the reaction.

Since, E^° (Ag⁺/Ag) has a greater positive value than E^° (H⁺/H), the reaction which is feasible at the cathode is given by

b) Limiting molar conductivity is the molar conductivity of the solution when the concentration of the electrolyte approaches zero (at infinite dilution).

The conductivity of an electrolyte solution is the conductance of ions present in a unit volume of the solution. The number of ions (required for conduction) decreases when the solution is diluted or the concentration is decreased. As a result, the conductivity of an electrolyte solution decreases with the decrease in concentration.

The elements having incompletely filled d-orbitals either in their ground state or in any of their oxidation states are known as transition elements.
Characteristics of transition elements are as follows:
1. They show variable oxidation states.
2. They generally form coloured compounds.