SOLUTION: You have 4L of an 90% aqueous solution of hydrochloric acid. You want 1L of a 25% solution. How much of the stock solution do you need to use?

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Question 834596: You have 4L of an 90% aqueous solution of hydrochloric acid. You want 1L of a 25% solution. How much of the stock solution do you need to use?
Found 2 solutions by Edwin McCravy, richwmiller:
Answer by Edwin McCravy(20055)   (Show Source): You can put this solution on YOUR website!
You have 4L of an 90% aqueous solution of hydrochloric acid. You want 1L of a 25% solution. How much of the stock solution do you need to use?
You are going to add water to the stock solution to make 1 liter.
Make this chart:

                 |         |           | Liters of
                 |Liters of|   Percent | pure acid 
                 | liquid  |    Acid   | contained
---------------------------------------------------
stock solution   |   x     |  90%=0.90 |   0.90x           
---------------------------------------------------
water            |  1-x    |   0%=0.00 | 0.00(1-x)  
===================================================
final solution   |   1     |  25%=0.25 |  0.25(1)

        
 
                             

                                  

                                      

                                      

                                          

                                          

Answer:  ths of a liter of stock solution, and ths of a liter of water.

Edwin
Answer by richwmiller(17219)   (Show Source): You can put this solution on YOUR website!
point of view of acid
.9x=.25(x+y),
x+y=1
x=0.277778 acid , y=0.722222 water
check
.9(0.277778)=.25(1),
ok

point of view of water
.1(x)+y=.75*(x+y),
x+y=1
x=0.277778 acid , y=0.722222 water
check
.1(0.277778)+0.722222=.75*(1)
ok
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