Chemistry Test 277

Factors affecting electrolytic conductance are: 

Concentration of ions: The sole reason for the conductivity of electrolytes is the ions present in them. The conductivity of electrolytes increases with an increase in the concentration of ions as there will be more charge carriers if the concentration of ions is more and hence the conductivity of electrolytes will be high. 

Nature of electrolyte: Electrolytic conduction is significantly affected by the nature of electrolytes. The degree of dissociation of electrolytes determines the concentration of ions in the solution and hence the conductivity of electrolytes.

Substances such as CH₃COOH, with a small degree of separation, will have less number of ions in the solution and hence their conductivity will also below, and these are called weak electrolytes. Strong electrolytes such as KNO₃ have a high degree of dissociation and hence their solutions have a high concentration of ions and so they are good electrolytic conductance.

Temperature: Temperature affects the degree to which an electrolyte gets dissolved in solution. It has been seen that higher temperature enhances the solubility of electrolytes and hence the concentration of ions which results in an increased electrolytic conduction.

When water is added to an aqueous solution the number of ions per unit volume decreases i.e., the concentration of ions decreases and hence thereby conductivity gets decreased.

Primary battery is a battery which cannot be recharged.

• A primary cell is a battery (a galvanic cell) that is designed to be used once and discarded, and not recharged with electricity and reused like a secondary cell (rechargeable battery).
• Primary cells cannot be recharged effectively because their reaction products are not in contact with the electrodes.
• Primary cells are made in a range of standard sizes to power small household appliances such as flashlights and portable radios.

During the charging of the lead storage battery, the sulphuric acid is regenerated.

• Sulphuric acid acts as an electrolyte in lead storage batteries.
• Thus, lead storage batteries can be used again and again by regenerating the sulphuric acid.

Applying a coating of zinc methods is suitable for preventing an iron frying pan from rusting.

• Applying paint and grease are not suitable solutions to prevent an iron frying pan from rusting as the paint can melt by flame and can be destroyed in repeated use.
• Applying a coating of zinc is a better option as it forms a coating of corrosion-resistant zinc which prevents corrosive substances from reaching the more delicate part of the metal.

Electricity is conducted through an electrolytic solution due to the movement of ions called electrolytic conduction.

Electrical conductance depends upon-

• Nature of electrolyte: The conductance of an electrolyte depends upon the number of ions present in the solution. Therefore, the greater the number of ions in the solution, the greater is the conductance.
• Concentration of the solution: The molar conductance of electrolytic solution varies with the concentration of the electrolyte. In general, the molar conductance of an electrolyte increases with decrease in concentration or increase in dilution.
• Temperature: The conductivity of an electrolyte depends upon the temperature. With increase in temperature, the conductivity of an electrolyte increases.
• Valence electrons per atom present in metals describes the electric conductance of it.
• Nature and structure is also a significant factors which influences electrical conductance.

As temperature increases, several changes occur that affect the rate of a chemical reaction:

• The average kinetic energy of molecules increases, leading to more frequent and energetic collisions.
• The fraction of molecules with energy greater than the activation energy increases, allowing more molecules to engage in effective collisions.
• These effective collisions are necessary for forming products, thus increasing the reaction rate.

Thus, the most appropriate answer would be option D

For producing the effective collisions, the colliding molecules must posses bimolecular reactions.

Bimolecular reaction originates from a collision between two reactants. Whether or not a collision results in a chemical reaction is determined by the energy of the reactants and their orientation.

The total energy of the two reactants must be in excess of the activation energy (Ea), and the reactants must be in a favorable orientation for the chemical reaction to occur. While there are many different orientations possible for the collisions, usually not all of them will result in a chemical reaction. For most reactions, if the orientation is not correct, the reactants will bounce off of each other without a chemical reaction.

The order of increasing acidic strengths of BF₃, BCl₃ and BBr₃ is: BF₃ < BCl₃ < BBr₃.

The extent of back bonding is maximum in BF₃ and minimum in BBr₃.

The actual reactions are:

NH₃ + NaOCl → NH₂Cl + NaOH

NH₂Cl + NH₃ → NH₂- NH₂ + HCl

NH₃ + HCl → NH₄Cl

NaOH + HCl → NaCl + H₂O

N₂O is not formed in the process.

Hence, option (d) is correct.

Ni²⁺: d⁸ configuration - 2 unpaired electrons

V²⁺: d³ configuration - 3 unpaired electron

Fe²⁺: d⁶ configuration - 4 unpaired electrons

Mn²⁺: d⁵ configuration - 5 unpaired electrons

So, the correct order of paramagnetic behaviour is Ni²⁺ < V²⁺ < Fe²⁺ < Mn²⁺.