stepwise process that dilutes an aqueous substance logarithmically. For example,

Question

stepwise process that dilutes an aqueous substance logarithmically. For example, to make a pH of 3, which is a 0.0010 M HCI solution, you could start with 5 mL of 1.0 M HCl and dilute to 50 mL, then take 5 mL of the resulting 0.10 M HCI solution and dilute to 50 mL and finally take 5 mL of the resulting 0.010 M HCI solution and dilute to 50 mL. Thus, a solution of 0.0010 M HCl is created with a pH of 3, as well as solutions of pH 1 and 2. A serial dilution can only be used to create strong acidic and basic solutions. For the middle ranges of the pH scale, buffer solutions must be created.

Explanation / Answer

Desired test sample concentration: pH of 11 NaOH then its pOH will be 3 (pH+pOH= 14) where the concentration of NaOH will be 0.001M (pOH = -log [OH-] ; [OH-] = 0.001 M)

First 5ml of 1 M NaOH is diluted to 50 ml---> 0.1 M NaOH (M1V1=M2V2 == 5 X 1 = 50 X M2) pOH=1 and pH=13

Second 5ml of 0.1 M NaOH is diluted to 50 ml ----> 0.01 M NaOH (M1V1=M2V2 == 5 X 0.1 = 50 X M2) pOH=2 and pH=12

Third 5ml of 0.01 M NaOH is diluted to 50 ml ----> 0.001 M NaOH (M1V1=M2V2 == 5 X 0.01 = 50 X M2)  pOH=3 and pH=11

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