### Determine weight of drug from molarity and volume of the solution

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

4.2.1.1) Molarity - general Normal 1

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How many grams of NaCl (MW = 58.5 g/mol) should be dissolved in 450 mL of a solution so that the strength is 0.95 M?

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lb equals 25.00875 g 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 450 mL, or 0.45 L.

[1] Using formula method:
M=g/(aV) therefore g=MaV
g=0.95 × 58.5 × 0.45 = 25.00875 grams. Ans.

[2] Using conceptual method:
First, count the number of moles (n) of NaCl present in this solution. 0.95 M means, there is 0.95 number of moles of NaCl present in 1000 mL of the solution.Therefore,
(0.95\quad mol)/(1000 \quad mL)=x/(450 \quad mL) therefore x = 0.4275 \quad mol
Then, calculate how many grams of NaCl will be contained in 0.4275 mol. Mole (n) is the gram weight (g) divided by molecular weight (a), or n=g/a. Therefore, g = n × a = 0.4275 \quad mol × (58.5 \quad g/(mol)) = 25.00875 g. Ans.