Mercury can be obtained by reacting mercury(ii) sulfide with calcium oxide. how many grams of calcium oxide are needed to produce 42.0 g of hg? 4hgs(s) + 4cao(s) > 4hg(l) + 3cas(s) + caso4. show all the work

The number   of grams of Ca)  needed to produce  42.0 g of Hg  is calciulated  as below
 4 HgS + 4CaO = 4 Hg + 3 Cas +CaSO4 

calculate the moles of Hg  produced
moles=mass/molar mass

moles of Hg =  42 g/200.59 g/mole = 0.2094 moles

by use of mole ratio of  Cao:Hg  which is 4:4 the moles of CaO = 0.2094 x4/4 =0.2094 moles

mass of CaO=moles x molar mass of CaO

mass of caO=0.2094 x56 = 11.73  grams