Question

During Part I of the water Analysis series, you prepared a Stock solution of Nitrate ion containing 250.0 mg N/L. In the second part of this experiment, you will use this Stock solution to prepare four Standard solutions to be used to make a calibration plot. As described in the background information for this experiment, the concentration of Nitrogen in these standards should be between 1 and 10 mg N /L.

A.) Describe HOW you are going to prepare a standard solution which must contain 8.0 mg N/L. Assume you are going to use a 250-mL volumetric flask for this preparation. Be sure to include necessary CALCULATIONS !

B.) Another one of the standard solutions should have the concentration of 10.0 mg N /L. Show calculations to be used for preparation of 250.0 mL of this solution.

Answer 1

Preparation of solutions from stock solution

A) To prepare a 250 ml of 8 mg N/L solution

using,

Volume of stock needed = final concentration required x final volume of solution/concentration of stock

Fedding the values,

Volume of stock solution needed = 8 mg N/L x 250 ml/250 mg N/L

                                                     = 8 ml

So, we would mix 8 ml of stock solution with 242 ml water to get 8 mg N/L solution

B) To prepare a 250 ml of 10 mg N/L solution

using,

Volume of stock needed = final concentration required x final volume of solution/concentration of stock

Fedding the values,

Volume of stock solution needed = 10 mg N/L x 250 ml/250 mg N/L

                                                     = 10 ml

So, we would mix 10 ml of stock solution with 240 ml water to get 10 mg N/L solution