Post Lab Questions:

1. How did your group choose the two reactants for this experiment?

We looked at the solubility chart and saw which combinations of ions would form a precipitate. Based on that, we decided to choose magnesium sulfate heptahydrate and potassium carbonate as our two reactants.

2. What kind of reaction is this? How do you know?

This reaction is a double-replacement reaction. We know this because the reactants are two ionic compounds. In this experiment, the two ionic compounds reacted by exchanging cations to form two different compounds. Double-replacement reactions are driven by the formation of a precipitate, a gaseous product, or a molecular compound. In our reaction, a precipitate formed, so the reaction is most likely a double-replacement.

3. a) Write a complete ionic equation for the reaction observed in this experiment.

Mg2+(aq) + 7H2O(aq) + SO42-(aq) + 2K+(aq) + CO3

2-(aq) MgCO3(s) + 2K+(aq) + SO42-(aq) + 7H2O(aq)

b) Indicate which ions are spectator ions in this reaction. Where are they found in this experiment?

In this reaction, the spectator ions are sulfate (SO42-) and potassium (K+). They are found dissolved in the

water.

c) Write a net ionic equation for this reaction.

Mg2+(aq) + CO32-(aq) MgCO3(s)

4. Explain how your group determined what procedure(s) to adjust for the second experiment. Did your modification(s) improve or worsen your experimental yield? Why?_____

5. What protocol modification(s) would you recommend for a third experiment?

_____

6. What is the actual yield of your precipitate in both experiments?

The actual yield of our precipitate in both experiments was 0.92 grams and 2.4 grams.

7. What is the percent yield of your precipitate in both experiments?

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The percent yield of our precipitate in both experiments was 46% and 120%.8. Calculate the percent error in your production of precipitate for both experiments, using the expected value of 2.00 grams. What is the relationship between percent yield and percent error?

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Percent yield is a measure of the efficiency of a reaction, while percent error is the percent that a measured value differs from the accepted value.

For each of the following questions, assume that you start with 2.00 grams of each of the same reactants used in your experiment. Show all calculations!

9. Which compound is the limiting reactant?

The magnesium sulfate heptahydrate (MgSO4 · 7H2O) is the limiting reactant.

10. Which compound is the excess reactant? Where can it be found? Suggest an additional experimental step to prove that you correctly identified which compound is in excess.

The potassium carbonate (K2CO3) is the excess reactant. It can be found _____

11. What is the theoretical yield of each of the products produced from this experiment?

The theoretical yield for each of the products produced from this experiment—magnesium carbonate and potassium sulfate—are 0.684 grams and 1.41 grams, respectively.

12. How many grams of precipitate would be produced if the other reactant was the limiting reactant?

If potassium carbonate, rather than magnesium sulfate heptahydrate, was the limiting reactant, then 1.22 grams of precipitate would have been produced.