Stoichiometry Investigation Lab!

Today in chem class we conducted an experiment in which we were to determine whether or not stoichiometry accurately predicts the mass of products produced in chemical reactions. The procedure was very similar to the Mole Ratio Lab we did in November, 2011.

*The balanced chemical equation for this reaction is:
Sr(NO₃)₂ + CuSO₄ --> SrSO₄ + Cu(NO₃)₂

*Therefore, since 2.00g of Strontiumnitrate completely reacts, the accepted value of grams of Strontium sulphate that is produced is:
2.00g x 1mol/211.6g x 1/1 x 183.7g/1mol = 1.736294896g or 1.74g

STRONTIUM NITRATE:

COPPER II SULPHATE:

In this experiment, 2.00g of Strontium nitrate (dissolved in water) was reacted with 3.00g of excess Copper II sulphate (dissolved in water). A precipitate was formed (Strontium sulphate), as well as a bright blue solution (Copper II nitrate). We separated the precipate by filtering, removed the water by drying, and found the mass by weighing.

The mass of Copper II sulphate used was 3.00g.The mass of Strontium nitrate used was 2.00g. The mass of the filter paper was 0.84g.The mass of precipitate and filter paper was 2.62g. And the mass of the precipitate (combination - filter paper) was 1.78g. 

According to our observations, 0.00969 moles of precipitate were formed. Calculations:
1.78g x 1mol/183.7g = 0.00969mol
(183.7g is the molar mass of Strontium sulfate)

The percent error in this experiment was 2.30% error. We are very pleased with these results.

Error exists in this experiment for a number of reasons. It is possible that our beakers were not entirely clean and contained other substances.There could have been miscalculations in measuring the amount of water and amount of copper II sulphate and strontium nitrate (it may not have been exactly 3.00g of Copper II sulphate and 2.00g of Strontium nitrate). It's possible that the filter paper was not dry enough (causing it to have a greater mass than it should). It's also possible that some precipitate may have transferred to our filter paper from other groups when they were shifted around in the drying oven.

Next class: Other types of problems!