lindsaypolgar
New member
The term “alum” refers to a class of compounds of general formula MM*(SO4)2.12H2O, where M and M* are cations of two different metals.
A 20.000 g sample of a certain alum is heated to drive off the water; the anhydrous residue weighs 11.123 g. Treatment of the residue an excess sodium hydroxide solution precipitates all the M* as M*(OH)3, which weighs 4.388 g. What are the identities of the two metals, M and M*, in the alum?
ps. I know that M* has to have a charge of 3 and that M has to have a charge of 1; I was already able to find that out. I just don't understand the rest......any help would be most appreciative. : )
A 20.000 g sample of a certain alum is heated to drive off the water; the anhydrous residue weighs 11.123 g. Treatment of the residue an excess sodium hydroxide solution precipitates all the M* as M*(OH)3, which weighs 4.388 g. What are the identities of the two metals, M and M*, in the alum?
ps. I know that M* has to have a charge of 3 and that M has to have a charge of 1; I was already able to find that out. I just don't understand the rest......any help would be most appreciative. : )