Chemistry Help Please: Molarity and Titrations.?

Question

Okay, so I'm in Chemistry I in college. I didn't have a good high school experience with chem, so it's biting me in the bum now.

I'm having the hardest time setting up the problems. I get how to do some of the calculations, but when I get a problem on a test, I can't pick out what information to plug in where. Here's one of the MANY questions I'm having a problem with:

"You have a 5.00 L solution of silver (I) nitrate. Suppose you want to convert the silver ions to silver metal. To do so, you will add zinc metal to reduce the silver ions. You first take a 3.00 mL sample of the silver (I) nitrate solution and find that it takes 20.0 mg of zinc metal to convert all of the silver ions in the sample to silver metal. What is the concentration of silver (I) nitrate? How much zinc (in grams) will be necessary to convert all of the silver ions in the 5.00 L solution to silver metal?"

I get that I need to find the molarity, but my book doesn't have problems similar to this.

I'm just at a loss of where to begin. I'm sure it's really simple, but I just don't get it. Also, if you are willing to help me with other problems please let me know!!!

Answer 1

Akways, always, in these problems, go by way of moles.

Don't try to memorise "ways of doing problems"; get to the principles behind the stage scenery.

How many moles Zn in 20.0 mg?

So how many moles of Ag+ were there in your 3 mL sample (Care! Each Zn reacts with TWO Ag+).

This tells you amount of Ag+ in your 3 mL sample. Amount divided by volume is concentration,the same concentration as in the 5.00L you had to start with. Take it step by step from there.