<PRE><B>Question 522537</B>
How much pure acid shoud be mixed with 2 gallons of an 80% acid solution in order to get a 90% acid solution?) 
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Equation:
acid + acid = acid
0.8*2 + 1.0x = 0.9(2+x)
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Multiply thru by 10 to get:
8*2 + 10x = 9*2 + 9x
x = 2 gallons (amt. of pure acid needed)
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Cheers,
Stan H.</PRE>