Lab Report-Determination Of A Formula By Analysis

Determination of a Formula by Analysis

Principle:

Determine the percent of Silver and Oxygen in Silver Oxide to determine the empirical formula.

Experimental Procedure:

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.

Raw Data:

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

Calculations:

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

Ag1.719O1

The empirical formula for silver oxide is Ag2O.

The balanced equation: 2Ag2O ? 4Ag + O2

Answers and Questions:

Do not heat with yellow flame at any time. Why? Because heating with a yellow flame will cause soot to form at the bottom of the crucible.