Question

A 1.5g sample of a compound, consisting of elements chlorine and chromium, was dissolved completely in water. The solution was added to excess silver nitrate solution, AgNo3. All the chlorine from the samplebwas converted to 4.074g of silver chloride precipitate, AgCl. Determine the number of moles of Ag+ and Cl- in the silver chloride precipitate.

Answer 1

To determine the number of moles Ag+ and Cl-, we need to know the moles of AgCl that is produced from the process. We are given the mass of the AgCl, to convert to moles we use the molar mass which is equal to 143.32 g / mol. The from the dissociation equation of the salt, we relate the ions. We do as follows:

Moles AgCl = 4.074 g AgCl ( 1 mol / 143.32 g ) = 0.02843 mol AgCl

In solution, the dissociation equation of the salt would be

AgCl = Ag+ + Cl-

Therefore,

Moles AgCl = moles Ag+ = moles Cl- = 0.02843 moles

The number of moles silver ions and chloride ions would be 0.02843 moles each.