Question

Account for the following facts(a) the reduction of a metal oxide is easier if the metal formed is in liquid state at the temperature of reducation.(b) the reduction of Cr2O3 with AI is thermodynamically feasible, yet it does not occur at room temperature.

(c) pine oil is used in froth floatation method.

Answer 1

2. (a) A reaction is spontaneous if the free energy change is negative for the reaction. Free energy change depends on enthalpy, entropy and temperature according to the following equation, $\Delta G=\Delta H-T\Delta S$. Entropy value is higher in liquid state than the solid state and thus will make the free energy more negative.

(b) For the reactants to be converted into products, the free energy of the system must overcome the activation energy for the reaction. The principle source of energy for molecules is the kinetic energy they carry when they collide. Increase in temperature increases the kinetic energy of molecules and thus the number of fruitful collisions. This provides the necessary energy to overcome the activation energy barrier and allows a reaction to occur.

(c) Froth flotation is a process for separating minerals from gangue due to the differences in their hydrophobicity. Hydrophobic differences between valuable minerals and waste gangue are increased through the use of surfactants and wetting agents and hydrophobic particles form froth and float and are removed. Pine oil prevents the further mixing of the ore from gangue and acts as good substance for forming froth for the minerals. It also increases the non-wettability of mineral particles.