Determine volume of the solution from molarity and weight of drug

4. Moles and Molarity 4.2) Molarity 4.2.1) Molarity - general Molarity - general Normal 1

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A pharmacists needs to prepare 1.55 M of penicillin V potassium solution. If the quantity of penicillin V potassium is 270.63 g, then determine the volume of the solution, in milliliter unit. The molecular weight of penicillin V potassium is 388 g/mol.

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lb equals 450 mL kg

    Molarity is the number of moles (`n`) dissolved per liter of solution (`V`). Again, mole is the weight in gram (`g`) divided by the molecular weight (`a`).
    In this example, the volume of the solution is to be found out.

    [1] Using formula method:
    `M=g/(aV) therefore V=g/(Ma)=(270.63 \quad g)/((1.55 (mol)/L) × (388 g/(mol)))`
    `therefore V=0.45 \quad L` which is 450 mL. Ans.

    [2] Using conceptual method:
    First, count the number of moles (`n`) of penicillin V potassium present in this solution. Mole is the gram amount of the solute divided by molecular weight. Therefore, `n= (270.63 \quad g)/(388 \quad g/(mol)) = 0.6975 \quad mol`.
    Then, determination of the volume in which 0.6975 mol of penicillin V potassium will be present to give a molarity of 1.55. From the definition of molarity, 1.55 M means, 1.55 mole of solute will be dissolved in 1L of solution. Therefore, we can write,
    `(1.55 \quad mol)/(1 \quad L)=(0.6975 \quad mol)/x therefore x = 0.45\quad L = 450\quad mL` Ans.

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