Answer to Question #65125 in Chemistry for Harleen Brar

Question

For this question: show in absolute DETAIL your steps and explain when appropriate that how you’re preparing the desired standards for the scenario outlined below. (20 pts)

You are required to prepare a series of dilution from a 1L of 25 ppm calcium stock solution in order to obtain a calibration curve for the analysis of several water samples by AA. If you consider the Ca standards to be made are: 0.10 ppm, 0.30 ppm, 0.50 ppm, 0.60ppm, 0.80 ppm, 1.00 ppm, 2.00 ppm, 3.00 ppm, 4.50 ppm and 5.00 ppm. Moreover, the only resources available to you are the following:

- Volumetric flasks of 50 ml only available in unlimited quantity
- Only pipettes available for the task are 2 ml, 3 ml and 5 ml and they are not graduated.

Answer 1

Further the steps for preparation of a series of solutions for the calibration curve are described.
5.00 ppm – 2 x 5 ml of solution with 25 ppm of Calcium are put into the volumetric flask of 50 ml and topped with distilled water.
4.50 ppm - 2 x 2 ml and 5 ml of solution with 25 ppm of Calcium are put into the volumetric flask of 50 ml and topped with distilled water
3.00 ppm - 2 x 3 ml of solution with 25 ppm of Calcium are put into the volumetric flask of 50 ml and topped with distilled water.
2.00 ppm - 2 x 2 ml of solution with 25 ppm of Calcium are put into the volumetric flask of 50 ml and topped with distilled water.
1.00 ppm - 2 ml of solution with 25 ppm of Calcium are put into the volumetric flask of 50 ml and topped with distilled water.
0.80 ppm - once the solution of 5 ppm is prepared, 5 ml and 3 ml has to be taken from the flask. The remaining amount has to be emptied. Once the flask is empty, taken portion of 5 ml has to be put there and topped with distilled water
0.60 ppm - once the solution of 3 ppm is prepared, 5 ml and 3 ml and 2 ml has to be taken from the flask. The remaining amount has to be emptied. Once the flask is empty, taken portion of 5 ml has to be put there and topped with distilled water.
0.50 ppm - once the solution of 5 ppm is prepared, 5 ml has to be taken from the flask. The remaining amount has to be emptied. Once the flask is empty, taken portion of 5 ml has to be put there and topped with distilled water.
0.30 ppm - once the solution of 5 ppm is prepared, 3 ml has to be taken from the flask. The remaining amount has to be emptied. Once the flask is empty, taken portion of 5 ml has to be put there and topped with distilled water
0.10 ppm – once the solution of 1 ppm is prepared, 5 ml has to be taken from the flask. The remaining amount has to be emptied. Once the flask is empty, taken portion of 5 ml has to be put there and topped with distilled water.