Determination of a Formula by Analysis
Place a clean porcelain crucible without lid onto a wire triangle on a tripod or ring. Heat the crucible for several minutes to a dull red heat using the hottest blue flame that the Bunsen burner will produce. Allow crucible to cool to room temperature then weigh it on an analytical balance to the nearest 0.001g. Handle the crucible only with forceps and carry it in a clean, dry beaker. Cover the crucible with all of the Silver Oxide and weigh precisely again. Heat crucible until there is no further change that can be observed. Repeat the process again until a constant weight is obtained, signifying the reaction is complete.
Weight of crucible + silver oxide = 18.178g
Weight of empty crucible = 16.884g
Weight of silver oxide = 1.294g
Weight of AgO + crucible after heating = 18.085g
Weight of after second heating = 18.075g
Weight of silver = 1.191g
Weight of oxygen = 0.103g
Take the weight of the silver and divide by the weight of silver oxide and multiply by 100 to find the percent of silver in silver oxide.
1.191gAg/1.294gAgO * 100% = 92.0% of Ag in AgO
Repeat with the oxygen.
0.103gO2/1.294gAgO *100% = 8.0% of O2 in AgO
Derive the formula of silver oxide.
92gAg/107gAg = 0.8598 mol Ag
8gO/16O = 0.50 mol O
0.8598 mol Ag/0.50 mol O = 1.719
0.50 mol O/0.50 mol O = 1
The empirical formula for silver oxide is Ag2O.
The balanced equation: 2Ag2O ? 4Ag + O2
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