EXPERIMENT #16 DETERMINATION OF THE CONCENTRATION FAN NKNOWN CaCT To combine gra

Question

EXPERIMENT #16 DETERMINATION OF THE CONCENTRATION FAN NKNOWN CaCT To combine gravimetric and volumetric data to calculate concentrations of solutions. To apply limiting reactant calculations to chemical problems. Prelab I. Lab. Describe how you know what the limiting reagent in today's lab will be. How 2. Computation. If 5.00 mL of o.100 M Baci, is combined with 10.0ml of o.0500 M NayPO, much (mol solid Bay(POa. can be formed? When two solutions are added together and a precipitate is formed, the quantity of the tate will be controlled by the solution not in excess. When is added to an excess required to produce the precipitate will allowthe molarity of the Caci2 solution to be Na CaCl2 CaCO, (s) 2Naci In Part I, a Calcium Chloride solution of known molarity will be used and the percent emor will be calculated. In Part Il, a concentration MD for an unknown CaC12 solution will be PART 1: MOLARITYoF A KNowNSOLUTION (DAY ONE) l, obtain a 25 ml pipet, bulb, Buchner Funnel, and filter flask from the stockroom. 2. Place approximately 40 mL of a 1 M solution of in a 250 mL 250 exactly or a of Cach into the beaker. Stir thoroughly with a glass stirring rod and rinse any precipitate on the stirring rod back into the beaker with deionized water 4 Set up the Buchner funnel, filter flask, and the hose line to the vacuum as demonstrated. Weigh a piece of filter paper and a Petri dish together (t0,0001 g) and record the weight on your data sheet. Place the filter paper in the Buchner funnel 6 Turn the vacuum on low and wet the filter paper with deionized water from a wash bottle. Using a glass stirring rod with a rubber policeman on the end, slowly begin to pour the contents of the 250 mL beaker onto the filter paper rum the vacuum up ifthe liquid is not being forced through the filter paper and into the Hask Be careful not to turn the vacuum up too high for the precipitate will seep through Continue pouring the contents of the beaker onto the filter paper. As the precipitate collects on the filter paper, it may be necessary to spread it out with your stiming rod to help drain any solution trapped by the precipitate. you have finished pouring the solution, remove as much as possible any ofthe remaining precipitate in the beaker with your policeman. Any residual precipitate still in the beaker and on the stirring rod must be washed off and on to the filter paper with deionized (use the deionized water sparingly.). Immediately after, rinse the beaker thoroughly in the sink. Otherwise, the beaker will be stained. uet the filter paper remain in the Buchner funnel for a couple of minutes, the vacuum will dythe filter paper and precipitate making it easier to remove from the Buchner funnel. 55

Explanation / Answer

1) If both the solutions of CaCl2 and Na3PO4 are unknown, it is not possible to calculate the limiting reactant in the precipitation experiment.

2) If the product is contaminated with dried salt, the mass difference between the theoretical mass of product to be obtained and the experimental value of precipitate formed would give us the value of excess salt precent in solution.

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