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
Total tried: Correct: Wrong:
How many grams of calcium chloride (MW = 111 g/mol) should be dissolved in 600 mL of a solution so that the strength is 0.8 M?
Click on the button below to see the answer and explanations
lb equals 53.28 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 600 mL, or 0.6 L.
[1] Using formula method:
`M=g/(aV) therefore g=MaV`
`g=0.8 × 111 × 0.6 = 53.28` grams. Ans.
[2] Using conceptual method:
First, count the number of moles (`n`) of calcium chloride present in this solution. 0.8 M means, there is 0.8 number of moles of calcium chloride present in 1000 mL of the solution.Therefore,
`(0.8\quad mol)/(1000 \quad mL)=x/(600 \quad mL) therefore x = 0.48 \quad mol`
Then, calculate how many grams of calcium chloride will be contained in 0.48 mol. Mole (`n`) is the gram weight (`g`) divided by molecular weight (`a`), or `n=g/a`. Therefore, `g = n × a = 0.48 \quad mol × (111 \quad g/(mol)) = 53.28` g. Ans.