Question

why sodium ethyl xanthate is used in froth floatation?

Answer 1

Sodium Ethyl Xanthate is relatively stable at high pH and rapidly hydrolyses at pH less than 9 at STP. It is the conjugate base of the unknown strong acid with $pK_{a}$ of 1.6 and $pK_{b}$ estimated as 12.4 for the conjugate base. Also sodium ethyl xanthate easily adsorbs on the surface of solid sulfides. Due to these properties it is used more in this process.
Some more examples of collectors are Potassium Amyl Xanthate, Potassium Isobutyl Xanthate etc.