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.
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.
34
15.625mL
To calculate the volume of concentrated HNO3 needed to prepare a stock solution, you can use the formula:
Volume of concentrated solution = (Desired concentration x Final volume) / Concentration of concentrated solution
1. For the first question, we have:
Desired concentration = 0.25 M
Final volume = 1000 mL
Concentration of concentrated HNO3 = 68% (or 0.68)
First, convert the desired final volume to liters:
Final volume (L) = 1000 mL / 1000 = 1 L
Now, calculate the volume of concentrated HNO3:
Volume of concentrated solution = (0.25 M x 1 L) / 0.68
To use the given density of HNO3, we need to convert grams to milliliters:
Density of HNO3 = 1.513 g/cm^3
Volume of HNO3 needed (mL) = (Volume of concentrated solution (L) x Density of HNO3 (g/cm^3) x 1000 mL) / (1.0 g/cm^3)
2. For the second question, we need to determine the volume needed to dilute the stock solution to a 500 mL volumetric flask, considering a 10-fold dilution.
To achieve a 10-fold dilution, the final concentration will be 1/10th of the stock solution's concentration. So the desired concentration is:
Desired concentration = 0.25 M / 10
Using the same formula as before, we can calculate the volume of the diluted solution:
Volume of diluted solution = (Desired concentration x Final volume) / Concentration of stock solution
Desired concentration (M) = 0.25 M / 10
Final volume = 500 mL
Concentration of stock solution = 0.25 M
Now, calculate the volume:
Volume of diluted solution = (0.025 M x 500 mL) / 0.25 M
Keep in mind that when performing dilutions, it's important to accurately measure volumes and mix the solutions thoroughly to ensure proper dilution.