### Dilution Problem - Find quantity of solvent

9. Altering Product Strength 9.1) Dilution 9.1.1) Dilution

9.1.1.1) Find initial concentration in dilution Easy 1

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Calculate the quantity of solvent you need to add into 27.5 mL of a 20.75 % solution to prepare a 6.41 % solution? Click on the button below to see the answer and explanations

lb equals 61.5 mL kg

This is a volume expansion or concentration dilution type problem. The essential formula is Q_1C_1 = Q_2C_2.
Here,

Q_1 = initial quantity = 27.5\quadmL.
C_1 = initial concentration = 20.75\quad%
Q_2 = final quantity = ?\quad mL.
C_2 = final concentration = 6.41\quad %

Therefore, rearranging the formula, we get:
Q_2 = (Q_1 × C_1)/(C_2) therefore Q_2 = (27.5 × 20.75) /6.41=89\quad mL in nearest whole number.

Now, subtract the initial quantity of the solution (27.5\quadmL) from this final quantity (89\quadmL) to determine the amount of solvent to be added: 89\quadmL-27.5\quadmL=61.5\quadmL. (Ans)