Relating Moles to Coefficients in a Chemical Equation

Name: ______Pd: ______

Mole Ratios in a Single Replacement Reaction

Background: The coefficients in a balanced chemical equation represent the relative number of moles of each reactant or product involved in the reaction. The ratios of these coefficients represent the mole ratios that govern the reaction. Stoichiometry and a balanced chemical equation can be used to predict the number of moles or mass of a product that can be produced from a known mass of reactant. In this lab a single replacement reaction will be performed and the experimental mole ratio will be compared to the mole ratio from the balanced equation.

Pre Lab Questions: A mass of 0.98g of copper (II) chloride (CuCl2) was dissolved in water. A piece of aluminum wire with a mass of 0.56g was placed in the solution. The blue color of the CuCl2 soon faded and a red precipitate of solid copper was observed. After the reaction was complete the mass of the aluminum wire remaining was 0.43g.

1. Write a balanced equation for the single replacement reaction described above.

2. What is the mole ratio of CuCl2 to Al from the balanced equation? ______3. Based on the experimental data above, determine the number of moles of each reactant. The molar mass of CuCl2 is ______.

4. Based on the experimental data what is the mass of Aluminum that was used?

5. Use the mass of Aluminum to predict the number of moles and mass of each product formed. Purpose:  Determine the mole ratio of iron to copper in the single replacement reaction between iron and copper (II) sulfate and compare it to the ratio from the balanced chemical equation.  Calculate the theoretical yield of copper based on moles of reactant.  Determine the percent yield of copper for the reaction.

Materials: iron filings copper (II) sulfate pentahydrate (CuSO4  5H2O) Distilled water Stirring rod 150 ml beaker 400 ml beaker 100 ml graduated cylinder weighboats (2) balance beaker tongs wire gauze

Procedure: 1. Turn the hot plate onto a medium setting. 2. Measure and record the mass of a clean, dry 150 mL beaker.

3. Measure approximately 12 grams of CuSO4 5 H2O in the larger weigh boat. Add it to the 150 mL beaker and record the combined mass (beaker + copper (II) sulfate).

4. Measure 50 mL of distilled water in the graduated cylinder and add this to the CuSO4 5 H2O in the beaker.

5. Heat this solution on the hot plate until the CuSO4 5 H2O is dissolved. Use the stirring rod to stir the solution. Do not allow the solution to boil or overflow! When all of the solid is dissolved, remove the beaker from the hotplate using the tongs and place it on the wire gauze. Do not shut off the hot plate. 6. Measure approximately 2.0 grams of iron filings in the smaller weighboat. Record the exact mass of the filings in the data table. 7. While stirring, add the iron filling to the copper (II) sulfate solution and allow the reaction mixture to stand for 5 minutes to ensure compete reaction. You will see a precipitate begin to form. Record observations in the data table. 8. Use the stirring rod to decant the liquid into a 400 mL. beaker, making sure none of the solid gets into the beaker. 9. Add 15 mL (measure in graduated cylinder) of distilled water into the beaker (washing the sides and the solid product). Swirl vigorously to wash off the solid. Let the solid settle and decant again. 10.Repeat step # 9. 11.Using your stirring rod, spread the solid out on the bottom of the beaker (make sure no solid remains on the stirring rod) and place the beaker on the hot plate to dry the solid. 12. When the solid is dry remove the beacker from the hot plate with the tongs and place it on the wire gauze. 13. When the beaker is cool, measure and record the mass of the beaker and the product. 14. The product may be scraped into the trash. . Dispose of the other solution as directed by the teacher and wash both beakers until there is no residue. Data Table:

Mass of empty 150 mL beaker

Mass of 150 mL beaker and CuSO4 5 H2O

Mass of CuSO4 5 H2O

Mass of iron filings

Mass of 150 mL beaker and dried product

Mass of dried product

Observations

Results and Discussion:

1. In this lab, reaction is a single replacement between Iron and copper (II) sulfate. Write the balanced equation, assuming that Fe on the products side will have a +2 charge.

2. What evidence was observed that confirmed that a chemical reaction occurred?

3. Based on the chemical equation, what is the identity of the solid product?

4. Determine the mass of dried copper that was produced and record it in the table above.

5. Convert the mass of copper produced to moles of copper. 6. Determine the number of moles of iron that reacted.

7. What is the experimental mole ratio of iron to copper?

8. Compare the experimental mole ratio to the mole ratio from the balanced equation. Why do you think there is a difference?

9. Using the number of moles of iron that reacted and the balanced equation, determine the number of moles and mass of copper that should have formed (theoretical yield).

10. Determine the percent yield using the following formula:

Percent Yield = Actual Yield X 100 Theoretical Yield

Conclusion: Brainstorm what the conclusion for the lab report would be. Remember that it should answer the purpose of the lab.