Question

A student determines the zinc content of a solution by first precipitating it as zinc hydroxide, and then decomposing the hydroxide to zinc oxide by heating. How many grams of zinc oxide should the student obtain if her solution contains 42.0 mL of 0.566 M zinc nitrate?

Answer 1

moles zinc nitrate=.042*.466 Zn(NO2)2

moles zinc= same number

Moles ZnO=same number

grams Zn oxiide= moles ZnO*formula mass.

Answer 2

mols Zn(NO3)2 = M x L = ?
You can get 1 mol Zn(OH)2 from 1 mol Zn(NO3)2; therefore mol Zn(OH)2 = mols Zn(NO3)2.
The same reasoning tells you that you can obtain the same number of mols ZnO.
g ZnO = mols x molar mass.