Question

a) Write the evidence of Arrhenius theory of electrolytic dissociation.
b) Explain any five terms in cell terminology.

Answer 1

a) Evidence in favour of Arrhenius theory of electrolytic dissociation:

• The enthalpy of neutralisation strong acid by strong base is a constant value and is equal to 57.32KJ gm $equi{v}^{-1}$. This aspect is well explained by adopting. Arrhenius theory of electrolytic dissociation. Strong acids and strong bases are completely ionized in water and produce $H^{+}$ and $O{H}^{-}$ ions respectively along with the counter ions. The net reaction in the acid-base neutralisation is the formation of water from $H^{+}$ and $O{H}^{-}$ ions. $H^{+}+O{H}^{-}\to H_{2}O;\Delta H_F^O=57.32KJmo{l}^{-1}$
• The colour of certain salts or their solution is due to the ions present. For example, copper sulphate is blue due to $C{u}^{2+}$ ions. Nickel salts are green due to $N{i}^{2+}$ ions. Metallic chromates are Yellow due to $Cr{O}_4^{2-}$ ions.
• Ostwald's dilution law, common ion effect and solubility product and other such concepts are based on Arrhenius theory.
• Chemical reactions between electrolytes are almost ionic reactions. This is because these are essentially the reaction between oppositely charged ions. for example, $A{g}^{+}+C{l}^{-}\to AgCl$
• Electrolytic solutions conduct current due to the Presence of ions which migrate in the presence of electric field.
• Colligative properties depend on the number of particles present in the solution . Electrolytic solution has abnormal colligative properties. For example, 0.1 molal solution of $NaCl$ has elevation of boiling point about twice that of 0.1 molal solution of non-electrolyte. The abnormal colligative properties of electrolytic solutions can be explained with theory of electrolytic dissociation.

(b) Cell terminology:

• Current is the flow of electrons through a wire or any conductor.
• Electrode is the material, a metallic rod/bar strip which conducts electrons into and out of a solution.
  
• Anode is the electrode at which oxidation occurs. It sends electrons into the outer circuit. It has a negative charge and is shown as $(-)$ in cell diagrams .
  
• Cathode is the electrode at which electrons are received from the outer circuit. It has a positive charge and is known as $(+)$ in cell diagrams:
  
• Electrolyte is the salt solution in a cell.
  
• Anode Compartment is the compartment of the cell in which oxidation half reaction occurs. It contains the anode.
• Cathode compartment is the compartment of the cell in which reduction half reaction occurs. It contains cathode.
  
• Half-Cell: each half of an electrochemical cell, where oxidation occurs and the other half where reduction occurs is the half cell.