Question

A hydrate of zinc nitrate has the formula Zn(NO3)2 . xH2O. If the mass of 1 mol of anhydrous zinc nitrate is 63.67% of the mass of 1 mol of the hydrate, what is the value of x?

Answer 1

MM Zn(NO₃)₂ = 189.36 g/mol

mass 1 mol Zn(NO₃)₂ = 189.36 g

mass hydrate = 100 / 63.67 x 189.36 = 297.409 g

mass 1 mol hydrate = 297.409 g

MM hydrate = 297.409 g/mol

MM hydrate = MM Zn(NO₃)₂ + MM xH₂O

297.409 = 189.36 + x(18)

x = 6