Homework Help: chemistry

Posted by Anonymous on Monday, August 29, 2011 at 5:47pm.

A 25.0 mL sample of 1.00 M KBr and a 75.0 mL sample of 0.800 M KBr are mixed. The solution is then heated to evaporate water until the total volume is 50.0 mL. What is the molarity of the KBr in the final soltion?

chemistry - Davis, Monday, August 29, 2011 at 5:58pm
Use the Molarity Formula
Molarity= moles/liters of solution
Molarity= moles/0.050 Liters
To find moles you have to find the moles of each sample of KBr. SO 1.00M KBR times .025liters =.025moles
And then 0.800M KBR times .075liters=.060moles.
Then you add the moles of both samples and get .085 moles.
SO you plug it into the equation:
Molarity= 0.085moles/0.050liters
Molarity=1.7mol/L

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