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MCAT Chemistry Question — Dilution Equation

A student prepares a ten liter solution of 0.01M NaOH by starting with 25mL of a stock solution. What is the concentration of the stock solution?


A) 0.1 M

B) 0.4 M

C) 2.5 M

D) 4.0 M





The student is only adding water when doing the dilution. Thus moles i = moles f. Because M = mol / volume, you can substitute M x V for moles. Thus the dilution equation is:


M1V1 = M2V2


Plugging in the values given, we get:


(0.01M)(10L) = (0.025L) x M2


0.1 moles = 0.025 L x M2


0.1 / 0.025 = M2


100 / 25 = M2


4 = M2


Therefore, (D) is the answer.


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