<PRE><B>Question 657808</B>
How much of a 75% solution of ethanol should a chemist add to 1500 mL of a 40% solution to obtain a 50% solution?
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Equation:
active + active = active
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0.75x + 0.40*1500 = 0.50(x+1500)
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75x + 40*1500 = 50x + 50*1500
25x = 10*1500
x = (2/5)1500
x = 600 mL (amt. of 75% solution needed)
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Cheers,
Stan H.</PRE>