Dilution Problem - Find quantity of solvent

9. Altering Product Strength 9.1) Dilution 9.1.1) Dilution 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?

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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`.

    `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)