Potassium dichromate (K2Cr2O7) is a carcinogen. However, it still plays a useful

Question

Potassium dichromate (K2Cr2O7) is a carcinogen. However, it still plays a useful chemistry role in some procedures. Suppose you need to make a 0.1000 M K2Cr2O7 solution from a 1.000 M stock solution. Using glassware from Question 1, how would you prepare the smallest quantity of this 0.1000 M solution? (Give a detailed answer with full explaination)

Consider this... Shelby needs to make a 3.00 M acetic acid solution from an acetic acid standardized solution that is 15.0 M. The analytical equipment available to Shelby in the lab includes the volumetric flasks and pipets shown below. Although several different size volumetric flasks are available, Shelby opts to use the 100-mL flask because it i:s both clean and dry. 500 mL TC@25 250 mL TC@25 100 mL TC@25 50 ml S ml

Explanation / Answer

Here we have to prepare smallest quantity of 0.1000 M solution.

Smallest quantity volumetric flask is 25 mL.

Now find the how much volume of 1.000 M stock solution required to prepare 25 mL of 0.1000 M K2Cr2O7 solution.

M1V1 = M2V2

Where M1 is initial molarity (1.000 M)

V1 is initial volume

M2 is final molarity ( 0.1000 M)

V2 is final volume (25 mL)

V1 = (0.1000 M × 25 mL)/ (1.000 M)

V1 = 2.5 mL

Hence volume of stock solution required is 2.5 mL.

But 2.5 mL pipette is not available. So we unable to prepare 25 mL of 0.1000 M solution.

Now consider second smallest quantity of volumetric flask i.e 50 mL.

Required volume of stock solution is,

V1 = (0.1000 M × 50 mL) / 1.000 M

V1= 5.0 mL.

Procedure to prepare 50 mL of 0.1000 M solution.

Take 50 mL volumetric flask and 5 mL pipette.

Pipette out 5 mL of 1.000 M K2Cr2O7 solution into 50 mL volumetric flask. And then make up with distilled water upto the mark.

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