Mr(K2O)= 39*2+16= 78+16= 94
Mr(Na2SO4)= 23*2+32+16*4= 46+32+64= 110+32= 142
Mr(Al(OH)3)= 27+16*3+3*1= 27+48+3= 30+48= 78
Mr(Zn3(PO4)2)= 65*3+31*2+16*8= 195+62+128=385
