Analytical Chem istry - DePauw University

36 Analytical Chemistry 2.0b. 313 – 273.15 =c. 712 × 8.6 =d. 1.43/0.026 =e. (8.314 × 298)/96485 =f. log(6.53 × 10 –5 ) =g. 10 –7.14 =h. (6.51 × 10 –5 ) × (8.14 × 10 –9 ) =5. A 12.1374 g sample of an ore containing Ni and Co was carried throughFresenius’ analytical scheme shown in Figure 1.1. At point A the combinedmass of Ni and Co was found to be 0.2306 g, while at point Bthe mass of Co was found to be 0.0813 g. Report the weight percentNi in the ore to the correct number of significant figures.6. Figure 1.2 shows an analytical method for the analysis of Ni in oresbased on the precipitation of Ni 2+ using dimethylglyoxime. The formulafor the precipitate is Ni(C 4 H 14 N 4 O 4 ) 2 . Calculate the precipitate’sformula weight to the correct number of significant figures.7. An analyst wishes to add 256 mg of Cl – to a reaction mixture. Howmany mL of 0.217 M BaCl 2 is this?8. The concentration of lead in an industrial waste stream is 0.28 ppm.What is its molar concentration?9. Commercially available concentrated hydrochloric acid is 37.0% w/wHCl. Its density is 1.18 g/mL. Using this information calculate (a) themolarity of concentrated HCl, and (b) the mass and volume (in mL) ofsolution containing 0.315 moles of HCl.10. The density of concentrated ammonia, which is 28.0% w/w NH 3 , is0.899 g/mL. What volume of this reagent should be diluted to 1.0 × 10 3mL to make a solution that is 0.036 M in NH 3 ?11. A 250.0 mL aqueous solution contains 45.1 µg of a pesticide. Expressthe pesticide’s concentration in weight percent, in parts per million,and in parts per billion.12. A city’s water supply is fluoridated by adding NaF. The desired concentrationof F – is 1.6 ppm. How many mg of NaF should be added pergallon of treated water if the water supply already is 0.2 ppm in F – ?13. What is the pH of a solution for which the concentration of H + is6.92 × 10 –6 M? What is the [H + ] in a solution whose pH is 8.923?