• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Decomposition of CuCO3

Free essay example:



Cu2O is a red crystalline material, which is produce by the electrolytic or furnace method. CuO is a black powder prepared by the ignition of suitable salts such as carbonate (1)

The mole is the mass of substance that has the same number of particles as atoms in exactly 12g of carbon-12. One mole of any substance contains Avogadro’s number 6.02×10²³ molˉ1 (2).Avogadro discovered that at room temperature (25°C) and pressure (1 atm), all gases occupy the same volume. 1 mole of any gas will occupy a volume of 24dm³.


The best method is to take one of the two equations and try to prove or disprove it. Since equation 2 has only 1 mole of every substance this would be the easiest to work out in terms of ratio. This assumption is made because the equation is “stoichiometric” (3) meaning 1 mole of CuCOз decomposes to exactly 1 mole of CuO and 1 mole of carbon dioxide. However, 24000cm³ would be too much gas to produce in a school lab, as that size of apparatus is not available. Gas syringe will be used but has a maximum of 100cm³, so it would not be sensible to produce 100cm³ of gas because if equation 1 turns out to be correct (which would mean oxygen will also be produced), and there would consequently be more gas. Aiming to produce 75cm³ of gas would leave room for error and the possibility of equation 1 occurring.

Equation 2: CuCOз ➔ CuO + CO2

If 1 mole of CuCOз produces 24000cm³ of CO2, to produce 75cm³ (for equation 2) we need:

Moles in gas                                         =        volume / 24000

                                                         =        75 / 24000

Moles in gas                                        =        0.003125 moles

Ratio                                                 =        CO2                :        CuCOз

                                                        1                :        1

                                                        0.003125        :        0.003125

Moles of CuCOз                                =        0.003125 moles

R.A.M of CuCOз                                =        63.5 + 12 + (16 × 3)

                                                =        123.5

Mass of CuCOз                                =        0.003125 × 123.5

                                                =        0.3859375

Mass of CuCOз needed to be decomposed        =        0.39g (2 s.f)

Equation 1: 2CuCOз ➔ Cu2O + 2CO2 + ½O2

For equation 1, volume of gas that will be produced using 0.39g of CuCOз will be:

Moles of 2CuCOз                                =        mass / R.A.M

                                                =        0.39 / 123.5

Moles of 2CuCOз                                =        0.003157894 moles

Ratio                                                 =        2CuCOз        :        2CO2

                                                =        2                 :        2

                                                =        0.00315784        :         0.00315784

Moles of 2CO2                                =        0.00315784 moles

Volume of 2CO2                                =        moles × 24000

                                                =        0.00315784 × 24000

                                                =        75.78816cm³

Volume of 2CO2                                =        76cm³


  • 0.39g of CuCOз        
  • Bunsen burner
  • Heat proof mat
  • Tripod
  • Gauze
  • Bung
  • Conical flask
  • Delivery tube
  • Gas syringe
  • Clamp
  • Scales (capable of weighing out 0.01g)


  • Collect and set up apparatus as shown in the drawing
  • Ensure the gas syringe is at 0 before the experiment begins.
  • Place the weighed mass of CuCOз into the conical flask and insert the bung tightly so that no gas escapes.
  • Light the Bunsen burner and place it underneath the test tube (as shown in the drawing).
  • Heat the conical flask until the CuCOз has fully decomposed. (This will be indicated by the fact that the bubbling will stop, and there will be a significant colour change of the CuCOз form bluish green to black or red).
  • Continue to heat even after the bubbling has stopped for about 1 minute. This will ensure that the reaction has completely ended
  • Leave the apparatus unattended to for a few seconds to ensure all gas has been released.
  • Then record the reading from the gas syringe which shows the volume of gas produced.
  • Repeat theses stages thrice, to get a more accurate result. Then take the average for the results.


In previous calculation, 0.39g of CuCO³ should produce 75cm³ of gas, if equation 2 is correct. If this volume of gas or a slightly less volume (to allow for slight gas loss) is obtained during the experiment, then equation 2 is correct. But if more than 75cm³ of gas is produced, then it means that another gas has been produced which will be oxygen. This would then mean that equation 1 is correct.

Also, after the decomposition has fully occurred, you can try to guess which equation is happening through looking at the colour of the substance after decomposition. If it’s a red compound, it may be equation 1 occurring due to the Cu2O which is a red crystalline. Whereas if it’s a black compound then it may be equation 2 occurring as CuO is a black powder.


CuCOз is harmful; ingestion may cause nausea or vomiting, and inhalation may cause irritation (4).

Care must be taken when dealing with Bunsen burner to avoid been burnt.



(2)     OCR Chemistry 1 - p20


This student written piece of work is one of many that can be found in our AS and A Level Inorganic Chemistry section.

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Related AS and A Level Science Skills and Knowledge Essays

See our best essays

Related AS and A Level Inorganic Chemistry essays

  1. effects Concentration and Temperature on the Rate of Reaction

    This means that that rate equation so far is as follows: Rate = k[BrO3] Results With Respect to Potassium Bromide The table below shows my results when varying the concentration of potassium bromide: Concentration of Potassium Bromide (mol/dm-3) Time Take For the Mixture to Turn Colourless (seconds)

  2. Thermal Decomposition of Calcium Carbonate

    The thermometer ranged from 0oC to 100oC, in graduations to 1oC, so I could read the thermometer accurately and round the temperatures to the nearest centigrade. In the thermometer, there is a reservoir which is where the thermometer detects the heat.

  1. Titration-chemistry OCR

    for counting atoms. The amount of substance is: > Given by the symbol n. > Measured using an unit called mole (mol) A mole is the amount of substance that contains as many single particles as there are in exactly 12g of carbon 12 isotope.

  2. The Effects of Strong and Weak Acids on the Order of a Reaction.

    Acids The definition of an acid is a substance which will donate a proton. This definition was made by Br´┐Żnsted-Lowry and was an adjustment of the Arrhenious definition - 'An acid is a compound that will form hydrogen ions in water and contains hydrogen'.

  1. Thermal Decomposition of Copper Crabonate

    Equation 1: 2CuCO (s) CuO (s) + 2 CO (g) + 1/2 O (g) (21/2 moles of gas) From this I can see that equation 1 will give off more gas, with a ratio of 5:4 to the gas given off in equation 2. Therefore I will base the mass of copper carbonate used, on equation

  2. Essay on the Oxides of Period 3 Elements

    Sodium oxide is the strongest base among all the oxides in period 3 as it contains the most oxide ions. The sequence is from forming metal hydroxide and dissociate into metal ions and hydroxide ions. As mentioned above, the basicity of the oxides decreases across the period.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work