Question

Grams, approximately of $NaCN$ are needed to extract $20\, g$ of gold from ore is ____$( Au =197)$
$4 Au +8 NaCN +2 N _{2} O + O _{2} \rightarrow 4 Na \left[ Au ( CN )_{2}\right]+4 NaOH$

Answer 1

$\underset{\underset{197}{4\times 197}}{4 Au} +\underset{\underset{788}{8\times 49}}{8 NaCN} +2 H _{2} O + O _{2} \rightarrow 4 Na \left[ Au ( CN )_{2}\right]+4 NaOH$

For $20\, gm$ approximately $10\, gm$ of $NaCN$ is required.