To extract gold from its ore, the ore is treated with sodium cyanide solution in the presence of oxygen and water. 4 Au(s) + 8 NaCN(aq) + O2(g) + 2 H2O(l) 4 NaAu(CN)2(aq) + 4 NaOH(aq)
(a) Determine the mass of gold that can be extracted if 21.7 g sodium cyanide is used.

(b) If the mass of the ore from which the gold was extracted is 161.5 g, what percentage of the ore is gold?

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c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.