# concentration prob

Discussion in 'MCAT: Medical College Admissions Test' started by V4viet, Feb 20, 2007.

1. ### V4viet Member 5+ Year Member

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A studetn has 0.8 L of a 3 molar HCL solution. How many liters of distilled water must she mix with 3 molar solution in order to create a 1 molar HCL solution?

a)0.8L
b)1.6L
c)2.4L
d)3.2L

Here's what i got so far
i found the moles of HCL in 3 molar solution which is
3 mol/1L x 0.8L =2.4 moles
then i dont know what else to do

Examkrackers has the prob worked out in the back but i still dont understand can someone please help me.. the answer is 1.6L

2. ### Mark84 5+ Year Member

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your looking into the problem to much M1V1= M2V2 so you would have
(3molar)(.8 Liters) = (1molar)(Xliters) solving for X you get 2.4 liters, now you started with .8 liters, so subtract .8 from 2.4 giving you 1.6 Liters

3. ### Richter915 7+ Year Member

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the formula is M1V1 = M2V2 but you must remember that V2 is the total volume of ur final solution. You already have .8L of HCL so you must dilute it with 1.6L of water to give you a total solution volume of 2.4L

4. OP

### V4viet Member 5+ Year Member

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omg thank you so much you guys.. yeah examkrackers never really mention M1V1=M2V2..and i guess it's been so long since gen chem that i forgot about it..thanks again guy..yal save my life...

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