Question

A mysterious compound which is suspected of being either FeCl2, NiCl2, or ZnCl2 needs to be identified. To do so a 1.98 gram sample is dissolved in water, and 22.38 mL of a 1.30 M solution of AgNO3 is required to completely precipitate out the chloride ion. What is the name of the compound?

Answer 1

Mysterious compound is ZnCl₂.

Step-by-step explanation:

AgNO₃ reacts with Cl⁻ in a 1:1 reaction producing AgCl(s). Moles of Ag that react are:

0,02238L × (1,30mol/L) = 0,02909 moles of Ag ≡ moles of Cl⁻. As the suspected compounds have 2 moles of Cl per mole of compound moles of compound are:

0,02909 moles of Cl⁻ ÷ 2 = 0,01455 moles.

As the mass of the sample was 1,98g. The molar mass of the suspected compound is:

1,98g/0,01455mol = 136,1 g/mol

Molar mass of FeCl₂ is 126,8g/mol, of NiCl₂ is 129,6g/mol and of ZnCl₂ is 136,3g/mol

That means mysterious compound is ZnCl₂

I hope it helps!