Answer:
We need 64.7 mL of this concentrated HClO4 solution
Explanation:
Step 1: Data given
Percentage of HClO4 solutions = 70.0 %
Density of HClO4 = 1.664 g/mL
Volume of prepared HClO4 solution = 500.0 mL
Molarity of the prepared HClO solution = 1.50 M
Step 2: Calculate mass HClO4
Let's assume we have 1 L = 1000 mL of solution
Density = mass / volume
Mass = density * volume
Mass = 1.664 g/mL * 1000 mL
Mass = 1664 grams
For a 70.0 M HClO4 solution the mass HClO4 is:
1664 g * 0.70 = 1165 grams HClO4
Step 3: Calculate molarity
1165 g HClO4 / 100.5 g = 11.59 moles HClO4 per L = 11.59 M
Step 4: Calculate the volume needed
C1V1 = C2V2
⇒with C1 = the molarity of the 70.0 % HClO4 = 11.59 M
⇒with V1 = the volume of the 70.0 % HClO4 = TO BE DETERMINED
⇒with C2 = the molarity of the prepared HClO4 solution = 1.50 M
⇒with V2 = the volume of the prepared HClO4 solution = 500.0 mL = 0.500 L
11.59 * V2 = 1.50 M * 0.500
V2 = (1.50 * 0.500) / 11.59
V2 = 0.0647 L = 64.7 mL
We need 64.7 mL of this concentrated HClO4 solution