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redXI August 18th, 2006 02:13

simple gravimetric
 
How many grams of NaCl are required to rpecipitate practically all the Ag ions from 2,5 x 10^2 mL of 0,0113 M AgNO3 Solution?? How about the net ionic equation for the reaction.

How do I it? I know the concepts fine but when the question is modified like this, I can't do it. Thanks for helping me out...I really need to study for my test.
:roll:

sdekivit August 18th, 2006 07:02

NaCl(s) + Ag(+) --> Na(+) + AgCl (s)

now you have the stoichiometry and you can calculate the amount of mol NaCl needed. Then you only need to convert that to gram.

redXI August 18th, 2006 19:46

Quote:

Originally Posted by sdekivit
NaCl(s) + Ag(+) --> Na(+) + AgCl (s)

now you have the stoichiometry and you can calculate the amount of mol NaCl needed. Then you only need to convert that to gram.

Okay. So I don't get it. It is AgNO3 that has volume and molarity then how is it possible for me calculate it? Where has that NO3 gone?? Sorry for asking too much :(

adrian August 19th, 2006 00:38

simple for others
 
You observed in the equation that you have mole/mole stoechiometry. Then your real problem is how many moles of AgNO3 you have in the solution.
The answer is: 2500 mL=2.5Lx0.0113=.. calculate yourself.
The result is exact No of NaCl moles you must use.
The last step is calculating the quantity of NaCl/ grams.
Concerning the "loss of NO3 ions": pls do not complicate the problem, is irrelevant.

sdekivit August 19th, 2006 06:52

Quote:

Originally Posted by redXI
Okay. Where has that NO3 gone??

You add solid NaCl to a solution containing Ag(+)-ions and NO3(-)-ions. since NaNO3(-) is soluble in water, it isn't necessary to write NO3(-) in the reaction equation, since NaNO3(aq) = Na(+)(aq) + NO3(-)(aq)

So we would get:

NaCl(s) + Ag(+) + NO3(-) --> Na(+) + NO3(-) + AgCl(s)

This is equal to:

NaCl(s) + Ag(+) --> Na(+) + AgCl(s)

redXI August 20th, 2006 00:42

Re: simple for others
 
Quote:

Originally Posted by adrian
You observed in the equation that you have mole/mole stoechiometry. Then your real problem is how many moles of AgNO3 you have in the solution.
The answer is: 2500 mL=2.5Lx0.0113=.. calculate yourself.
The result is exact No of NaCl moles you must use.
The last step is calculating the quantity of NaCl/ grams.
Concerning the "loss of NO3 ions": pls do not complicate the problem, is irrelevant.

how do I calculate the quantity of NaCl/grams?
Divide the mass with molar mass of NaCl??


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