Please show work ..ooo AT&T; 12:18 PM 3496 Experiment 7-... CHEM 403 Exp 7 Exper
ID: 551675 • Letter: P
Question
Please show work ..ooo AT&T; 12:18 PM 3496 Experiment 7-... CHEM 403 Exp 7 Experiment 7 ANALYSIS OF AN UNKNOWN CHLORIDE One of the important applications of precipitation reactions lies in the area of quancitative analysix. Many substances that can be precipitated from solution are so slighdly soluble that the precipitation reaction by which they are formed can be considered to proceed to cpletion Salver chloride is an example of such substance. If a solution contantg AE'e·s slowty added 10 dte containing Cl ion, the ions will react to foem AgC: (1 Silver chloride is so insoluble that essentially all ofthe Ag added will preoptate until all of the CT is used up. When the amount of Ag added to the solution is equal tothe amou of CT initially present, the precipitation ofCT ions will befor all practical pupes, co plete Aga A convenient method for chloride analysis using AgC has been devised. A solution of AgNO is added to a chloride solution just to the point where the number of moles of Ag added is equal to the mumber of moles of CT initially present. You can analyze foe CT by simply measuring how many moles of AgNO are required. This measurement is rather easilly made by an experimental procedure called a titration. In this titration, a solution of AgNOs of known concentration (in moles AgNOh per laer o solation) is added from a calibrated buret to a solution with a mcaured amount of unknosn The titration is stopped when a color change occurs the soltoa ihdicating ául ilochet tely equivalent amourts of Ag, and CI are present The color change is caused by a chema seage called an indicator, which is added to the solution at the beginning of the tieration The volume of AgNO solution that has been added up to the time of the color chane cn be measured accurately with the buret, and the number of moles of Ag added can be calculated from the known concentration of the solution. bn the Mohr mcthod or the volumetne analysas of chloride. which you will employthis experiment, the indicanor used is KCO. The chromate ion peesent in sollutions of is subitance will react with silver ion to foem a red peccipitate of Ag CrOs Under the conditions of the titration the Ag added to the solution rcacts preferentially with CT until that ion is essennially quenitly removed from the system, at which point Ag:CrOs begins to precipitale and the solution color changes from yellow to a reddish hue. The end point of the titration is that poin atwhich the co change is first observed In this experiment, weighed samples containing an unknown percmtags of ciloride wil be titrated with a standardized solution of AgNO, and the volumes of AgN0s solution required to reach the end poim of each titration will be measured Fromm the known molarity of the solution Mwo, and the measured volume used, pwo, te number of moles of Ag-added can be calculated MgoXF-o of moles AgNO no of moles Ag 2) Adapted from Slowinki E.J Wosey W C. Chemical Principles in the Laboraloryd 1 of 5 CHEM 403 Exp 7 Courses Calendar To Do Notifications MessagesExplanation / Answer
1. a)
No. of moles of Cl- = mass/ ionic mass = 0.221 g/ 35.5 g/mole = 0.00623 mole
b) Molarity of the solution = (1000 * no of moles of Cl- dissolved)/ volume of solution = (1000* 0.00623)/ 50 = 0.125 M
2. a) 1 mole AgNO3 reacts with 1 mole of Cl- ion.
43.75 ml of 0.05273 M AgNO3 soultion contains (43.75*0.05273)/1000 moles = 0.00231 mole of AgNO3
0.0231 mole of AgNO3 reacts with 0.0231 mole of Cl-
So, the sample contains 0.0231 mole of Cl-
b) grams of Cl- ion present = 0.00231 mole *35.5 grams/ mole = 0.082 grams
c) mass percent pf Cl- in sample = ((mass of Cl- in sample*100)/ mass of sample)% = (0.082*100)/0.3147 = 26.1%