Question

ydrate of zinc sulfate, ZnSO4 XH20, decomposes to produce 43.9% water. Calculate ter of crystallization (X), and write the formula for the hydrate. Formula of hydrate ZnSO4 H2O Water of crystallization

Answer 1

Let mass of compound = 100 g

mass percentage of water = 43.9 %

mass fraction of water = (mass percentage of water) / 100

mass fraction of water = 43.9 / 100

mass fraction of water = 0.439

mass of water in compound = (mass of compound) * (mass fraction of water)

mass of water in compound = (100 g) * (0.439)

mass of water in compound = 43.9 g

mass anhydrous ZnSO₄ = (mass of compound) - (mass of water in compound)

mass anhydrous ZnSO₄ = (100 g) - (43.9 g)

mass anhydrous ZnSO₄ = 56.1 g

moles water = (mass water) / (molar mass water)

moles water = (43.9 g) / (18.0 g/mol)

moles water = 2.439 mol

moles anhydrous ZnSO₄ = (mass anhydrous ZnSO₄) / (molar mass ZnSO₄)

moles anhydrous ZnSO₄ = (56.1 g) / (161.44 g/mol)

moles anhydrous ZnSO₄ = 0.3475 mol

moles water / moles anhydrous ZnSO₄ = (2.439 mol) / (0.3475 mol)

moles water / moles anhydrous ZnSO₄ = 7

Water of crystallization = 7 (seven)

There are 7 molecules of water per 1 molecule ZnSO₄

Formula of hydrate : ZnSO₄.7H₂O