Intro: In this experiment one is to determine the identity of two unknown substances by using stoichiometry with two chemical reactions that involve the unknown substances. By determining the weight of the salts that should be created by each substance, one can determine which substance is which by performing the chemical reaction and measuring the weight of the salt left over after the water is boiled off.
Experimental Procedure: Determine through stoichiometry what the expected weight of the left over salt will be from each reaction. Mark two beakers with a 1 and a 2 then weigh the beakers and record their starting weights. Put 30 mL of hydrogen chloride into each beaker. Then, measure out .15g unknown 1 and .15 g of unknown 2. Put unknown 1 into the beaker marked with a 1 and unknown 2 into the beaker marked with a 2. Mix both solutions until the unknowns are dissolved and the reaction ceases to produce carbon dioxide bubbles. Then, use the hot plate to boil the water off of the products in both beakers until just salt is left. Finally, weigh the beakers again and subtract the starting weights from the final weights to determine the weight of the salt produced. Determine what the unknowns are by comparing the weight of the salt in the beakers to the expected weights of the sodium bicarbonate versus sodium carbonate. Calculate percent yield.
Expected Weights of Salt Left Over
Starting Weight of Beaker (g)
Ending Weight of beaker (g)
Weight of salt left over (g)
Unknown 1 = Sodium Carbonate
Unknown 2 = Sodium Bicarbonate
% yield of Sodium Carbonate: 13% yield
% yield of Sodium Carbonate: 16% yield
Discussion: The data in this experiment do not line up directly with theoretical values due to common