SOLUTION: In a 10mL solution with 10% of solute (liquid) already in it, how much (mL) solute needs to be added to make the total solute content 20% in the 10mL solution? All my friends got a

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Question 285448: In a 10mL solution with 10% of solute (liquid) already in it, how much (mL) solute needs to be added to make the total solute content 20% in the 10mL solution? All my friends got an answer of 1.1mL. Can someone please tell me how this is calculated? Thank you.
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
In a 10mL solution with 10% of solute (liquid) already in it, how much (mL) solute needs to be added to make the total solute content 20% in the 10mL solution?
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Note: After you add the x amount of solute you have (10+x)mL of solution.
I assume the x amount you add is 100% active ingredient.
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Equation:
active + active = active
0.10*10 + x = 0.20(10+x)
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Multiply thru by 100 to get:
10*10 + 100x = 20*10 + 20x
80x = 10*10
x = 100/80
x = 1.25 mL
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Cheers,
Stan H.