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Which equation is correct?

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Which equation is correct?


Copper has two oxides, Cu2O and CuO.

Copper carbonate, CuCO3, decomposes on heating to form one of these oxides and an equation can be written for each possible reaction:

Equation 1:   2CuCO3 (s)Cu2O(s) + 2CO2(g) + ½O2 (g)

Equation 2:   CuCO3 (s)                 CuO(s) + CO2 (g)

I must determine which equation is correct.


From the two equations we can see when copper carbonate is heated or decomposed gases are given off. To find which equation is correct we can use ideas about moles, plan and design an experiment to measure a volume of gas that will prove which of the two equations is correct.

Therefore to find out the correct equation I will need to decompose the copper carbonate by heating and after this I will measure the amount of gas produced. The volume of gas will help me determine which equation is correct.

  • It is possible to determine which equation is correct by measuring the volume of gas given off by the decomposition.

Measuring the volume of gas will tell me which equation is correct from above. I will need to measure the mass of copper carbonate as this will tell me the amount of copper carbonate needed in grams for the experiment and if it is correct it will show me what equation is correct. Also the volume of gas given off depends upon the molar quantities.  

Equation 1:   2CuCO3 (s)Cu2O(s) + 2CO2(g) + 1\  2 O2 (g)

Equation 2:   CuCO3 (s)                 CuO(s) + CO2 (g)

Equation 2:

Gas used in experiment -30cm³

1 mole of any gas occupies 24000cm³

Therefore, the first thing I will need to do is find the moles. This is because the moles of copper carbonate are required to produce 30cm³ of gas.

Gas used in experiment30

The amount of which 1                     24,000           =1.25× 10 ֿ³ mole

mole of any gas occupies                          

Now that I have got the amount of moles the next step is to find the mass of copper carbonate. To do this I will need to multiply the moles and the RMM of copper carbonate.

The relative molecular mass of copper carbonate (CuCO3 ) is 123.50

I got this by adding copper, carbon and oxygen together. These were 63.50 for Cu, 12 for C and 48 for 3 oxygen’s.  

Mass of  CuCO3                                               = moles × RMM

                                                          = 1.25× 10 ֿ³ × 123.5

                                                          = 0.154

Rounded to 2 decimal places            = 0.15 (weight in grams of copper carbonate)

This now shows me that I need 0.15 grams of copper carbonate.

Therefore this shows that if I have 0.15 grams of copper carbonate, it will release and produce 30cm³ of gas if equation 2 is correct.

Equation 1:

2 moles of CuCO3 =2 and a half moles of gas

This is telling me that 2 moles of copper carbonate will produce 2 and a half moles of gas.

Since one mole of copper carbonate is 1.25× 10 ֿ³ and equation 1 shows us it has 2 moles of copper carbonate I will need to divide 2.5(total amount if gas produced in equation 1) by 2.

1.25× 10 ֿ³ moles = 2 and a half   × 1.25× 10 ֿ³ moles


                             =1.5625× 10 ֿ³ mole

                             =1.56× 10 ֿ³ moles of gas

I will be now calculating the amount of gas produced in equation 1, so I will be multiplying the mole by 1 mole of any gas which is 24000cm³.

Volume of gas = 1.56× 10 ֿ³   × 24000



Therefore the volume of gas for equation 1 is 37.4cm³. Also if I used 0.26 grams of copper carbonate, it will release and produce 37.4cm³ of gas.


  • Copper carbonate, CuCO3
  • Heatproof mat
  • Safety goggles
  • Bunsen burner
  • Spatula
  • Electric balance/Digital weighting scale
  • 50cm3 Gas burette
  • Boiling tube
  • Beaker
  • Rubber bung
  • Delivery tube
  • Lab coat
  • Bottle of distilled water

Risk Assessment




Action in case of accident

Copper Carbonate


Wear a lab coat and for eye protection wear goggles, also keep away from skin contact.

Wash thoroughly with running tap water.

Bunsen burner


Keep burner on yellow flame when not in use.

Cool part with running tap water. Report to teacher if serious.


Can cause injury when broken

Handle with care.

Report to teacher in case of injury.

Digital weighing scale/Balance

Electric shock and falling over plug wires

Make sure plug wires are safe were people cant fall over. Keep away from water.

Report to teacher if serious.


  1. First of all weigh 0.26grams CuCO3   and place it directly in the boiling tube.
  2. Then I will fill roughly 50 ml of water into the gas burette to the top.
  3. After this I will put my finger or thumb on top of the gas burette and turn it upside down into a beaker and uncover beneath the water surface. The beaker will also be filled with water. When placing the gas burette in the beaker which is full of water I have to make sure no water is lost otherwise it can have an affect on the experiment.
  4. Then I will need to place a one holed rubber bung on the test tube. Inside the hole I will enter the tubing.
  5. After all this I will need to get a bunsen burner and heat the copper carbonate.
  6. The gas burette will start to collect bubbles and every time this happens water will be lost and the gas will come out on top of the gas burette.
  7.  The rate of gas release will begin to slow down when decomposition is near completion. When the bubbling stops, remove the heat and the delivery tube at the same time.
  8. Finally read the gas burette to determine the amount of water displaced by the gas. I will also need to record the room temperature which is likely to be between 20 and 24 degrees Celsius.




The gas burette will be positioned with the help of a clamp.

The volume measured may need to be corrected because there can be the leakage of gas. I cannot be certain that there will be no leakage of gas therefore some gas can escape. The gas burette is not totally accurate and there maybe some human error such as when the gas burette is being read for its measurement. The weight of the copper carbonate measured may not be totally accurate and this can have an affect on the experiment or the volume of gas produced.

I am going to use a 50 cm3gas burette to collect the gas for the reason that a gas burette is more accurate and more reliable than a gas syringe and a measuring cylinder. The gas syringe is not reliable since it can get stuck and this will have a huge impact on the experiment. The measuring cylinder also has a disadvantage which is the accuracy of the readings are not correct or precise enough. Therefore I decided to use a gas burette since it is more accurate and more reliable than a gas syringe and a measuring cylinder.



  1. http://www.cci.unl.edu/Chemistry/MicroScale/MScale16.html


  1. School sheets-Plan
  2. Cambridge advanced sciences –chemistry 1-OCR___Page 71
  3. Classroom notes

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