Question $1$

a$)$ Define the term leaching. $[2]$

b$)$ State and explain $4$ factors that affect the leaching process. $[4]$

c$)$ Discuss with examples oxidative, reductive and chemical leaching. $[9]$

Question $2$

Distinguish between diffusion$-$controlled reactions and chemical controlled reactions giving examples in each case. $[6]$

Question $3$

a$)$ What is the electrode potential of the Ni$2+/$Ni reaction in sulphate solution at $25\backslash$deg C at a Ni$2+$ concentration of $0\mathrm{.}005$ M $($assumption: activity of Ni$2+$ is equal to its molar concentration$).[6]$

b$)$ At what pH is H$2$ at $10$ atm at equilibrium with this solution and pure nickel? $[6]$

Ni$2++2$ e $=$ Ni E$\backslash$deg $=-0\mathrm{.}26$ V

$2$H$++2$ e $=$ H$2$ E$\backslash$deg $=0\mathrm{.}00$ V

END