CHE 105 Intro to Chemistry Lab: Sample Lab Short Answer Decomposition of Malachite Data Analysis 1)

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CHE 105 Intro to Chemistry

Lab: Sample Lab

Short Answer

Decomposition of Malachite

Data Analysis

1). What is the stoichiometric ratio between the number of moles of copper (II) oxide produced in the reaction and malachite? The molar mass of malachite is 221.1 g/mol and the molar mass of copper (II) oxide is 79.55 g/mol. To calculate the mass of malachite, use the data you recorded using the balance.

2. Predict the mass of CuO expected from the decomposition of the malachite, based on the balanced equation and the mass of malachite used in this experiment. The molar mass of malachite is 221.1 g/mol and the molar mass of CuO is 79.55 g/mol.
3. Calculate the percent error in the experiment using the experimental mass of CuO and the theoretical mass of CuO. The percent error is defined as follows.?
    

 

 

Conclusions

1. What does your percent error indicate about the experiment? What are possible sources of error in this experiment?
2. Similar to malachite, copper (II) carbonate decomposes to form copper (II) oxide and carbon dioxide. Given the data in the table below, how many moles of copper (II) oxide were formed in the reaction. The molar mass of copper (II) oxide is 74.55 g/mol.

           

Decomposition of Malachite

 

1. What color was the malachite before heating?
   1. black
   2. magenta
   3. green
   4. grey
2. What color was the malachite after heating?
   1. black
   2. magenta
   3. green
   4. pink
3. How many grams of malachite did you add to the crucible?
   1. 5 g
   2. 95 g
   3. 10 g
   4. 98 g
4. How many grams of product were in the crucible after heating? Choose the closest answer.
   1. 2.805 g
   2. 98.000 g
   3. 95.195 g
   4. 7.195 g
5. By how much did the mass of the crucible's contents change after heating? Choose the closest answer.
   1. +7.195 g
   2. +2.805 g
   3. -2.805 g
   4. -7.195 g
6. The molar mass of malachite is 221.1 g/mol. How many moles of malachite were present before the reaction?
   1. 10.00 mol
   2. 0.04523 mol
   3. 0.09045 mol
   4. 1.000 mol
7. The product remaining in the crucible after heating is copper (II) oxide. The molar mass of copper (II) oxide is 79.55 g/mol. How many moles of copper (II) oxide were produced during the reaction? Choose the closest answer.
   1. 0.09045 mol
   2. 0.9045 mol
   3. 0.4523 mol
   4. 0.04523 mol
8. Which of the following represents the balanced chemical equation for this reaction?
   1. Cu₂CO₃(OH)₂ -> CuO + H₂O + CO₂
   2. Cu₂CO₃(OH)₂ -> 2CuO + H₂O
   3. Cu₂CO₃(OH)₂ -> CuO + CO₂
   4. Cu₂CO₃(OH)₂ -> 2CuO + H₂O + CO₂
9. Based on the number of moles of malachite that you started with, how many grams of water were produced? The molar mass of water is 18.0153 g/mol. Choose the closest answer.
   1. 1.630 g
   2. 1.982 g
   3. 1.815 g
   4. 0.8148 g
10. Based on the number of moles of malachite that you started with, how many moles of CO₂ were produced? Choose the closest answer.
    1. 0.09045 mol
    2. 1.000 mol
    3. 0.9000 mol
    4. 0.04523 mol
11. Based on the number of moles of malachite that you started with, how many grams of CO₂ were produced? The molar mass of CO₂ is 44.01 g/mol. Choose the closest answer.
    1. 3.981 g
    2. 1.991 g
    3. 0.4401 g
    4. 0.04523 g
12. Based on the number of grams of CO₂ and H₂O produced during the reaction, does this compensate for the observed loss of mass?
    1. No, because more copper oxide was produced. 
    2. No, because this violates the Law of Conservation of Mass. 
    3. No, because mass is conserved. 
    4. Yes, this compensates for the mass lost in the reaction.
13. You observed that the products in the crucible weigh less than the reactants that you added. How is this possible?
    1. Mass was lost due to experimental error.
    2. CO₂ and H₂O were released as gases.
    3. The malachite absorbed CO₂ from the air.
    4. Mass was converted to energy.
14. What kind of a reaction took place upon heating?
    1. synthesis
    2. decomposition
    3. single displacement
    4. double displacement
15. Baking soda is used as a leavening agent in baking. When heated, baking soda undergoes a decomposition reaction to form carbon dioxide. Given the data in the table below, which of the following reactions occurs during baking? The molar mass of baking soda is 84.007 g/mol and the molar mass of carbon dioxide is 44.01 g/mol.
    1. 2NaHCO₃  -> Na₂O + 2CO₂ + H₂O
    2. 2NaHCO₃  -> 2Na + 2CO₂ + H₂O
    3. NaHCO₃ -> NaOH + CO₂ 
    4. 2NaHCO₃  -> Na₂CO₃ + CO₂ + H₂O