Thermal decomposition of Copper Carbonate (CuCo3).

3: handle the equipment carefully.

Apparatus:

1. Water trough
2. Test-tube
3. Bunsen burner
4. One-holed rubber stopper
5. Plastic delivery tube
6. Graduated cylinder (250cm3)
7. Cling film
8. Top- pan balance
9. Analytical balance
10. Spatula
11. Sample container

Thermometer

Diagram:

   

Method:

1.  Place a clean, dry sample-container on top-pan balance and press           button read zero.  Than transfer about 2.0g of green powder of CuCo3 to sample container using spatula.
2.  Using analytical-balance weigh the mass of sample (CuCo3) and sample-container to three decimal places and record the reading.
3.  Transfer the sample to test-tube and reweigh the sample container and sample residues on the analytical balance and record the reading.
4.   Deduce the mass of sample (CuCo3) by subtracting the mass of sample-container sample –residues from the mass of sample and sample-container.
5.   Now set up the apparatus as shown in the diagram.
6.   Decompose the copper carbonate with blue flame for 10mins or until decomposed completely.  (High flame is not needed as the copper carbonate burns on a low blue flame) As the Carbon dioxide is collected in cylinder the water is replaced from graduation cylinder.  When the CuCo3 decomposed completely the bubbles stop.
7.  Waite until the temperature of carbon dioxide cool down to room temperature, because the volume of gas changes with temperature and pressure.  Measure the temperature in water as it is replaced with Co2 gas.    But water react with carbon dioxide while we wait, which will affect the volume of Co2 gas.  To prevent this reaction we have to saturate the water with carbon dioxide gas by passing the Co2 through water.
8.  After the Co2 cooled down to room temperature read the meniscus of water carefully and record the volume of carbon dioxide collected in the graduation cylinder.

Result:

Mass of sample (CuCo3)+sample-container = …g

Mass of sample residues+sample-container  =…g

Mass of sample (CuCo3)                               =…g

Volume of carbon dioxide                             =…cm3

Calculation:

In equation 1:

Mass of CuCo3           =…g

Molar mass of CuCo3 = 123.5g                        X/123.5 = …moles

No of mole of CuCo3 =…moles

The ratio of CuCo3 to Co2 is 1:1 so

No of moles of CuCo3 is = No of moles of Co2

Or

1 mole of Co2        = 24dm3 at 25C and 1 atm pressure

X moles of Co2            = volume of Co2 produced at 25C and 1 atm pressure

No of mole of Co2 = volume of Co2 produced in dm3 / 24dm3

Molar mass of Co2 = 44g

Mass of Co2           = no of moles of Co2 X 44 = …g

Mass of Co2           =…g

The ratio of CuCo3 to O2 is 2:1/2, so

No of moles of CuCo3 / 4 = no of mole of O2

1 mole of O2        = 24 dm3 at 25C and 1 atm pressure

No of moles of O2  = X dm3 at 25C and 1 atm pressure

Molar mass of O2 = 32g

Mass of O2                   = no of moles of O2 X 32g =…g

Mass of O2                   =…g

In equation 2:

The ratio between CuCo3 to Co2 is 1:1, so

No of moles of CuCo3 = No of mole of Co2

Or

1 mole of Co2        = 24dm3 at 25C and 1 atm pressure

X moles of Co2            = volume of Co2 produced at 25C and 1 atm pressure

No of mole of Co2 = volume of Co2 produced in dm3 / 24dm3

Molar mass of Co2 = 44g

Mass of Co2           = no of moles of Co2 X 44 = …g

Mass of Co2           =…g

When we performed the above calculation now we can deduce the no of moles and mass of the product formed from the decomposition of the copper carbonate.

Conclusion:

The correct balanced stiochiometric equation for the thermal decomposition of copper carbonate can be deduce while carry out the experiment and measure the correct amount of CuCo3 decomposed and the volume of carbon dioxide produced by applying the above calculation.

Bibliography:

OCR 3882 AS Chemistry practical manual/ pages 9,10and 17