Gold from Gold bearing rock can be dissolved with NaCN in presence of oxygen. `Au(s)_NaCN(aq)+O_(2)(g)+H_(2)O(g)+H_(2)O(l)rarrNa[Au(CN)_(2)](aq)+NaOH(aq)` For 200kg rock (containing 0.0197% gold) how many litres of 0.2M NaCN aqueous solution is required to dissolve all Gold present in rock. [Given: Atomic mass of Au=197]

Explanation

`4Au(s)+8NaCN(aq)+O_(2)(g)+2H_(2)O(l)rarr4Na[Au(CN)_(2)](aq)+4NaOH(aq)`
`W_(Au)=200xx(0.0197)/(100)xx10^(3)`
`n_(A_(u))=0.2`
`(n_(Au))/(4)=(n_(NaCN))/(8)`
`(0.2)/(4)=(0.2M)/(8)xxV` (lit)
V(lit)=2lit.