questions of dilution & gravimetric

[redXI]

I am now studying on my test and I came upon one question which I can't answer but I still remember that the answer is 1.09 M. Yeah, I have a bad memory... So, here goes:

A 46.2-mL, o.568 M calcium Nitrate [Ca(NO3)2] solution i smixed with 80.5 mL of 1.396 M calcium nitrate solution. What is the concentration? :shock:

ALSO....

Is it true that according to my teacher that we must use distilled water in the gravimetric analysis of chlorides?? Why is it so? Isn't it just the same if we use regular drinking water?

And yesterday, I have to answer this super tough question is the school and I got zero since I am not really good in chemistry and I'm a bit too shy to ask anything...This is the question:

If 30.0 mL of 0.150 M CaCl2 is added to 15.0 mL of 0.100 M AgNO3, what is the mass in grams of AgCl precipitate?

Thanks so much for helping me.
:oops: