Chem 312. Homework number 7. Due at class time on Friday April 6^th.

You need to show your working to get credit (just writing the answer, whether correct or not, will not get you any points). You can do this homework collaboratively, i.e. you can work in a group and hand in one set of solutions for the group. If you do, each member of the group needs to sign the front page of the material handed in to indicate that this was a genuine collaboration.

1. For an element of molar mass 50, what is the concentration, in ppm, of a 10.0 µmol L-1 solution? You have a stock 10.00 ppm solution. You want to make 50 mL of a 20 ppb solution. What volume (in µL) do you take? The ICP-OES detection limit for arsenic is 2 ppb. What is the detection limit in nmol L-1? For an element of molar mass 50, what is the concentration in mol L-1 of a 1.0 ppm solution? At. wt. As = 75 g mol-1.

2. Question 18-11 on page 391 of the Harris text.

3. Question 18-13 on page 391 of the Harris text.

4. Question 18-26 on page 393 of the Harris text.

5. Question 19-13 on page 418/419 of the Harris text.

6. Question 20-8 on page 443 of the Harris text.

7. Question 20-12 on page 443 of the Harris text.

8. A 25-mL portion of a sample solution is diluted to 50 mL with distilled water. To a second 25-mL portion is added 5.0 mL of 100 ppm strontium standard solution, and the mixture diluted to 50 mL. What concentrations of strontium have been added to (a) the first solution, and (b) the second solution? When sprayed into an atomic absorption spectrometer, the absorbances measured are 0.14 and 0.34. What is the strontium concentration in the original sample?