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Dilution. Is a process of making a solution less concentrated as in the addition of more solvent. Dilution. In diluting solutions, the amount of solute remains the same, but the amount of solvent changes. Since the amount of solute remains the same, therefore,
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Dilution • Is a process of making a solution less concentrated as in the addition of more solvent
Dilution • In diluting solutions, the amount of solute remains the same, but the amount of solvent changes. Since the amount of solute remains the same, therefore, n before dilution = n after dilution
If the concentration is given in molarity and the formula for molar concentration is M = n / V , the number of moles of solute is computed as n = MV If n1 = n2 substituting MV to n, the equation becomes M1V1 = M2V2
Sample Problem • How many milliliters of 0.900M solution can be prepared from 65.0mL of a 1.80M solution of salt Given: M1 = 1.80 V1 = 65.0mL M2 = 0.900M V2 = ? Solution: M1 V1 = M2V2 V2 = M1V1 = (1.80M )(65.0mL) =130 mL M2 0.900M
Ex:2 • Given the following values, describe how you would prepare 200.0mL of 0.200M KCl from 0.800 M KCl Given: V2 = 200mL V1 = ? M2 =0.200M M1 = 0.800M Solution: First determine how much 0.800M KCl is needed to prepare the solution by solving for V1 V1 = M2V2 = (0.200M)(200.mL) = 50.0ml M1 0.800M Place 50.0mL of 0.800M KCl solution in a 200mL volumetric flask and fill the flask with distilled water up to the 200mL mark
To express the solution of very dilute solution like those encountered in pollution, parts per million (ppm) is used ppm = mg solute . L solution
Example: • The Dead Sea is the saltiest sea in the world. It contains 332g of salt per 1000g of water. What is the concentration in parts per million (ppm)? Solution: ppm = mg solute . L solution convert 332g x 1 mg = 332,000mg . 0.001g Solve V solution using D = M / V, V = M / D V = 1000g x 1g = 1000mL = 1L . mL ppm = 332,000mg/ L
Classwork: • A 22.5 mL sample of 5.20M solution of nitric acid (HNO3) is diluted to 40.5mL. Calculate the molarity of the dilute solution • How many mL of 2.00M solution is required to prepare 3.00L of 1.20M NaNO3 solution?