To be honest I'm really not sure how I should look at a question like this. I did this so far:
0.6390 g of AgCl * (35.45g Cl / 1 mole Cl) = 22.65255g Cl
I'm not sure if that is a useful step or not or what the next one shall be that I take. Any guidance is appreciated.
No its not a useful step and I have no idea what you are doing here at all.
Think about it again you have a known weight of unknown composition.
ZnCl2 (aq) + 2 AgNO3 (aq) -> 2 AgCl (s) + Zn(NO3)2 (aq)
From this equation you know that for every mole of ZnCl2
in the sample you'll get 2 moles of AgCl solid.
You are told the sample gives 0.6390g of AgCl.
How many moles of AgCl is that.
How many moles of ZnCl2
does that mean were in the sample?
What is the weight of the ZnCl2
calculated from the no. of moles?
That weight of ZnCl2
divided by the sample weight give the %ZnCl2
in the sample.