Question

1. calculate the volume of concentrated HNO3 (68%)that is needed to prepare stock solution 0.25M in 1000mL volumetric flask. (density HNO3 = 1.513 g/cm^3)
2. from above stock solution, determine volume needed to dilute to 500mL volumetric flask that contained 10 times dilution.

Answer 1

1. What's the concn of the HNO3?
1.513 g/mL x 1000 mL x 0.68 x (1/molar mass HNO3) = ? mols/L = about 16.4 which probably should be rounded to 16 M since the 68% allows only two significant figures to be used.

mL1 x M1 = mL2 x M2
mL1 x 16 = 1000 x 0.25
Solve for mL1. Pipet mL1 volume into a 1L volumetric flask, add distilled H2O to the mark on the flask and mix thoroughly.

Answer 2

34

Answer 3

15.625mL