Question

3. You are a workstudy for the chemistry department. Your supervisor has just asked you to prepare 500mL of 3M HCl for tomorrow's undergraduate experiment. In the stockroom explorer, you will find a cabinet called "Stock Solutions". Open this cabinet to find a 2.0L bottle labeled "11.6M HCl". The concentration of the HCl is 11.6M. Please prepare a flask containing 500 ml of a 3 M (+/- 0.005M) solution and relabel it with its precise molarity. Note that you must use realistic transfer mode, a buret, and a volumetric flask for this problem.

As a reminder, to calculate the volume needed to make a solution of a given molarity, you may use the following formula:

C1V1 = C2V2

b)Calculate percentage error

Answer 1

I have to prepare 500mL of 3M HCl from 11.6 M HCl.

Formula: C1V1 = C2V2

Here, C1 = 3M, V1 = 500mL, C2 = 11.6M, V2= ?

so, V2=(C1V1)/C2 = (3M * 500mL) / 11.6M = 129.31 mL

To prepare 500mL of 3M HCl, I have to take 129.31mL of 11.6M HCl and then volume should be made up to 500mL (i.e. I have to add 370.69 mL of water).

For a realistic transfer mode, I have to take 130mL 11.6M HCl.(+370mL of water for 500mL of 3M HCl)

Now the actual molarity of HCl will be = (11.6M * 130mL) / 500mL = 3.016M (It is slightly higher concentration)

Percentage error = 0.54 %.

Thank you. Hope it will helps you.

answered by: anonymous