Name Section Experiment 10 Advance Study Assignment: Analysis of an Aluminum-Zinc Alloy 1. On the following page, construct a graph of No, vs. % Al. To do this, refer to Equation 11 and the discus- sion preceding it. Note that a plot of N vs. % Al should be a straight line (why?). To fix the position of a straight line, it is necessary to locate only two points. The most obvious way to do this is to find No, when % Al = 0 and when % A1 = 100. If you wish you may calculate some intermediate points (for example, Nu, when % Al = 50, or 20, or 70); all these points should lie on the same straight line. To use a spread- sheet, set up Equation 11 for different Al percentages. Graph Nyt, vs. % Al. 2. A student obtained the following data in this experiment. Fill in the blanks in the data and make the indicated calculations: Mass of gelatin capsule 0.1134 g 23°C Ambient temperature, 23+273=296 Mass of capsule plus alloy sample 0.3218 g Ambient temperature, T 296 K Mass of alloy sample, m g Atmospheric pressure 732 mm Hg Vapor pressure of H20 at 1 (Appendix I) Mass of empty beaker 154.3 g mm Hg Mass of beaker plus displaced water 401.6 g Mass of displaced water Pressure of dry H2 g PH, (Eq. 7) mm Hg Volume of displaced water (density = 1.00 g/mL) atm mL Pressure of dry HZ L Volume, V, of H2 = Volume of displaced water mL = Find the number of moles of H, evolved, nu, (Eq. 5; V in liters, Pit in atm, T in K, R= 0.0821 liter- atm/mole K). moles H2 Find, NH, the number of moles of H, per gram of sample (Mu,m). moles H/g Find the % Al in the sample from the graph prepared for Problem 1. % Al Find the % Al in the sample by using Equation 11. % A006C
Advance Study Assignment: Analysis of an Aluminum-Zinc Alloy 0.050 0.040 0.030 VHA 0.020 0.010 25% 50% 75% 100% % AI
(11) 100-%A1 -X0.0153 + 100 in Nu = (100X0.0556) We can solve Equation 11 directly for % Al if we know the number of moles of H, evolved per gram of sample. To save time in the laboratory and to avoid arithmetic errors, it is highly desirable to prepare % Al in the sample can be read directly from the graph. Directions for preparing such a graph are given in advance a graph giving Nh, as a function of % Al. Then when Nh, has been determined in the experiment, Problem 1 in the Advance Study Assignment.
