Question

25 ml AgNO3 reacts with 5 mM NaCl; 35 ml of the silver solution is required to titrate a sample of ZnCl2∙6H2O. How many milligrams of the hydrate are present in the sample?

Answer 1

ZnCl₂ + 2AgNO₃ = Zn(NO₃)₂ + 2AgCl

n(AgNO₃) = V(AgNO₃) ∙ C(AgNO₃) = 0.035 / (V(NaCl) ∙ 0.005 / 0.025) = 1.75 / V (NaCl)

m(ZnCl₂ ∙ 6H₂O) = 2 ∙ n(AgNO₃) ∙ M(ZnCl₂ ∙ 6H₂O) = 488.6 ∙ n(AgNO₃) = 279.2 ∙ V(NaCl)