SOLUTION: A 20% v/v solution of HCl is diluted by a ratio of 1:2, and then by a ratio of 1:4. Find the concentration of the resulting HCl solution.

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Question 1106365: A 20% v/v solution of HCl is diluted by a ratio of 1:2, and then by a ratio of 1:4. Find the concentration of the resulting HCl solution.

Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
20%281%2F3%29, the first dilution


20%281%2F3%29%281%2F5%29, the second dilution

1.33, percent HCl as v/v

Answer by ikleyn(52781) About Me  (Show Source):
You can put this solution on YOUR website!
.
A 20% v/v solution of HCl is diluted by a ratio of 1:2, and then by a ratio of 1:4. Find the concentration of the resulting HCl solution.
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0.  The initial composition is 1:4 :  1 volume of HCl to 4 volumes of water; 
                                      5 elementary volumes in all.



1.  First dilution:                   They add 2*5 = 10 volumes of water.
                                      We have now 1 elementary volume HCl and 4+10 = 14 volumes of water. 
                                      In all, there are 1 + 14 = 15 elementary volumes of the solution.



2.  Second dilution:                  They add 4*15 = 60 volumes of water.
                                      We have now 1 elementary volume HCl and 14+60 = 74 volumes of water. 
                                      In all, the final composition is 1 volume HCL and 74 volumes of water, 
                                      which gives the concentration 1%2F75 =  0.013333 = 1.3(3)%.