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

25 ml AgNO₃ reacts with 5 mM (Cl^-)

${\frac {25}{5}}={\frac {35}{x}}$

x = 7 mM.

n(ZnCl₂*6H₂O) = 7/2 = 3.5 mmol.

m(ZnCl₂*6H₂O) = 3.5*(65+71+6*18)/1000 = 0.854 g = 854 mg