SOLUTION: A chemist must mix 8 liters of a 70% solution of potassium chloride with some 40% solution to get a mixture that is a 50% solution. How much of the 40% solution should be use?

Question 757839: A chemist must mix 8 liters of a 70% solution of potassium chloride with some 40% solution to get a mixture that is a 50% solution. How much of the 40% solution should be use?
Answer by ptaylor(2198) (Show Source): You can put this solution on YOUR website!
Let x=amount of 40% solution needed
Now we know that the amount of pure potassium chloride that exists before the mixture takes place(8*0.70+0.40x)has to equal the amount of pure potassium chloride that exists after the mixture takes place(0.50(8+x)). Sooo
8*0.70+0.40x=0.50(8+x)
5.6+0.40x=4+0.50x subtract 4 and also 0.40x from each side
5.6-4=0.50x-0.40x
1.6=0.1x
x=16 liters ---amount of 40% solution needed
CK
8*0.70+0.40*16=0.50*24
5.6+6.4=12
12=12
Hope this helps---ptaylor

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