Experiment 1 1. Record the following: 2. Calculate and record the following: 3.

Question

Experiment 1

1. Record the following:

2. Calculate and record the following:

3. Use the mole ratio of CuO produced per mole of malachite to write a balanced equation for the malachite decomposition reaction. Assume that CO2 and H2O are also products of the decomposition.

4. Predict the mass of CuO expected to result from the decomposition of the malachite, based on the balanced equation and the moles of malachite calculated in 1d. The molecular weight of CuO is 79.55g/mol.

5. Calculate the percent error in the experiment using the experimental mass of CuO from question 1 and the theoretical mass of  CuO from question 4. The percent error is defined as:

|(experimental value) - (theoretical value)| / theoretical value * 100%

6. What does your percent error indicate about the experiment? What are possible sources of error in this experiment?

7. You observed that the products in the crucible weigh less than the reactants that you added. How is this possible?

a Mass of an empty crucible (g) 88.000 g b Mass of the crucible with malachite(g) 98.000 g c Subtract (a) from (b) to obtain the mass of malachite (g) 10 g d Divide (c) by the molecular weight of malachite (MW = 221.1 g/mol) to obtain the moles of malachite in the crucible 0.045 mol e Mass of crucible with CuO(g) 95.195 g f Subtract (a) from (e) to obtain the mass of CuO produced (g) 7.195 g

Explanation / Answer

2.a. moles of Cuo = 7.195/79.545 = 0.0905 mol

b. ratio of mols = 0.045/0.0905 = 1/2

   CuO : malachite = 1:2

3.

Cu2CO3(OH)2 (s) -----> 2CuO(S) + CO2(g) + H2O(g)

4. 1 mol malachite = 2 mol CuO

   mass of CuO produced = 0.045*2/1*79.55 = 7.159 grams

5.

   (7.195-7.159)/7.159*100 = 0.5%

6. there may measurment error.

7. because some of the products are gases, which are escaped from the crusible.

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