Is the formula of Copper Oxide the same regardless of how it is prepared?

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Is the formula of Copper Oxide the same regardless of how it is prepared?

Planning

Aim:

· To find and compare the formula of Copper Oxide using various different samples.

Introduction:

· Through my preliminary work I have found the following ways of producing samples of Copper Oxide:

1. Heating Copper powder/turnings in air.

2. Heating Copper Carbonate in air.

3. Heating Copper Hydroxide in air.

4. Heating Copper Nitrate in air.

5. Heating Copper Sulphate in air

· Experiments 1, 2 and 3 are all suitable methods of producing Copper Oxide.

· I have decided not to perform either of the last two ways because both give off poisonous gasses during production.

· I have chosen to perform the following 3 different experiments:

1. Reducing a pre-prepared lab sample of Copper Oxide

2. Reducing a sample made by heating Copper Carbonate in air

3. Oxidation of Copper Powder

Prediction:

· I believe that the formula of Copper Oxide will remain the same (i.e. CuO) regardless of how it is prepared.

· This is because the valency of both Copper and Oxygen is 2.

· Copper wants to lose both of its outer electrons to gain a complete outer shell. Oxygen needs to gain 2 electrons to achieve a complete outer shell.

· Therefore the process of Ionic bonding takes place and Copper gives up its 2 electrons to the Oxygen leaving an ionic formula of:

Cu²+ O²-

Justification:

· Investigating Chemistry by Davies, Denial, Locke and Reay says that:

“The Law of Constant Composition…states that all pure samples of the same chemical compound contain the same elements combined together in the same proportions by mass.”

· This justifies my prediction.

Variables:

· The key variable in this case is the mass of Copper Oxide/Copper powder that will be used.

· The masses that I will use are, 0.5g, 1g, 1.5g, and 2g.

· This is the same for both the Copper Oxide and Copper Powder.

· I will not be repeating any of the masses because as I am effectively performing each experiment four times and then taking an average so therefore I have, in a way, repeated the experiment four times.

· The only dependent variable is air pressure, which will have little or no effect on the results.

Apparatus List:

· Bunsen burner

· Retort stands

· Clamps and bosses

· Test tubes

· Tripod

· Pipe-clay triangle

· Crucible

· Tongs

· Heat-proof mat

· Safety Goggles

· Mass balance

· Tube with cotton wool inside it that has been soaked in Ethanol

Diagram:

For experiment 1 and the second part of experiment 2:

For the first part of experiment 2 and experiment 3:

Method:

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For experiment 1:

· Measure, using a mass balance the required amount of lab sample Copper Oxide and place in a pre-weighed test tube.

· Clamp this tube above the Bunsen as shown in the diagram.

· Into the clamped test tube place a tube containing a small piece of cotton wool soaked in ethanol. (This converts the methane passing through into a hydrogen-like gas).

· Attach the other end of the tube to a gas tap and slowly turn on the gas, as to not blow out the Copper Oxide.

· Leave the gas running for a minute or ...

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