Question

It is often necessary to prepare a dilute solution from a more concentrated solution rather than starting from a solid and just dissolving it then adding water. This technique is called serial dilution. Give all the steps necessary to obtain 100 mL of a 1.7 x 10-5 M solution using a solution prepared by dissolving 0.3 grams of a Red dye (molar mass of 869 g/mol) dissolved in water in a 100 mL capacity volumetric flask. Assume you have access to deionized water, 1.0mL pipette, 5.0 mL pipette, 10.0 mL pipette, and 100.0 mL volumetric flasks.

Answer 1

Answer:

Take 10.0mL of your original solution and dilute it to 100.0mL and then, take 5.0mL of this solution and dilute it in another flask to 100.0mL

Explanation:

The initial solution of 0.3g of Red dye in 100mL has a concentration of:

0.3g Red dye × (1mol / 869g) = 3.4x10⁻⁴ mol Red Dye in 100mL = 0.100L:

3.4x10⁻⁴ mol / 0.1L = 3.4x10⁻³M

As you want a 1.7x10⁻⁵M solution, you need to dilute your solution:

3.4x10⁻³M / 1.7x10⁻⁵M = 200 times

Having this in mind, you must find the dilutions you must make to achieve the 200 of dilution factor (Dilution factor is how many times you dilute a solution from a concetrated form).

If you dilute the original solution taking 10.0mL to 100.0mL you dilute the solution: 100.0mL / 10.0mL = 10 times.

Now, you need to dilute this solution another 20 times to achieve the 10*20 = 200 times of dilution.

If you take 5.0mL of the last solution and dilute it to 100.0mL you are diluting the solution 100.0mL / 5.0mL = 20 times.

The dilution is:

3.4x10⁻³M × (10.0mL / 100.0mL) × (5.0mL / 100.0mL) = 1.7x10⁻⁵M

Thus, to obtain the 1.7x10⁻⁵M solutionyou need to:

Take 10.0mL of your original solution and dilute it to 100.0mL and then, take 5.0mL of this solution and dilute it in another flask to 100.0mL