Actual mass of copper carbonate used = 10g (let this be M)
So the theoretical mass of copper produced = 127 x 10 = 5.14g
247
Experimental Readings
Mass of filter paper =0.1g
Mass of filter paper + copper =0.1g
Actual yield of Copper produced =<0.1g
Percentage yield = actual yield x 100%
theoretical yield
Evaluation
The percentage yield was not high enough, as only an extremely small amount of copper was gained from the experiment. This could have been due to low amounts of copper in the solution, and also if certain aspects of the experiment was not carried out properly, e.g. if it was not heated through properly or mixed properly then the yield may not have been as high as it could have been.
The method of extraction used to produce a yield may be improved by carrying out the test more accurately, more than once and comparing the results gained and looking at the most accurate results.
The theoretical yield calculated was 5.14g, but the actual yield we gained was less than 1 gram, meaning that the experiment conducted was less than 20% efficient.
There are many reasons why the actual yield may have been so low, and there are different ways in which we can combat this.
One reason why the yield was so low could have been that when conducting experiment, large amounts of oxygen/air was present, therefore allowing the already separated molecules of copper to react with the oxygen in the air, and reform copper oxide (which was used to start the experiment), therefore lowering the amount of copper produced.
There are various ways this could be dealt with:
- Airless/oxygen-less chambers could be used to completely minimalise the amount of oxygen in the air, therefore preventing the reformation of copper oxide. Though this method should work very well to get the actual yield closer to the theoretical yield, it may be costly to set up and equipment may be hard to get hold of, and may not be possible.
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Another way of combating this problem is by using a gas, in this case hydrogen. By using hydrogen we can cause the oxygen in the air to react with the hydrogen to form Water (H2O). We could use the hydrogen by blowing it over the top of the test tube we are using to heat up our copper solution so that any oxygen in the air around the test tube combines with the hydrogen to produce water.
Many of these solutions are also used in industry (like the blowing over of gas to reduce the amount of oxygen in the air when producing copper).
If this method is too costly or you simply can’t have access to the materials and equipment needed, one way of gaining a higher actual yield of copper would be to, after finishing the first experiment, scoop out and allow to dry the already processed copper mixture. Once it is dry, repeat the heating process, and use additional carbon powder if needed. You may be able to acquire more copper from your mixture, allowing the same batch to be more (cost) efficient. Though this is a slightly more resourceful method, it is also very impractical.
Alternative Methods of Copper Extraction
One method of extraction of copper in industry is electrolysis. Some metals can be extracted through redox reactions.
Electrolysis consists of putting the metal into a molten substance, allowing the positive anodes to leave the element, causing negative cathodes to join the substance (in this case copper, if negative sulphur cathodes are added then copper sulphate is produced).
The Industrial Process of Refining Copper Ore
The raw ore first needs to be crushed into smaller pieces. The ore is crushed in to 25cm pieces and then using water and 13cm steel balls, the ore is ground up into 1cm pieces. The unwanted rock settles out using froth flotation, which concentrates the ore. Using a blast furnace, the copper ore is burnt with oxygen to produce matte, iron is removed as slag and sulphur comes off as sulphuric dioxide. The matte is placed into a converter furnace and air is blown through, which removes iron and sulphur to blister copper. Natural gas is blown into the anode furnace to burn off any remaining oxygen in the melt. The copper melt is cast into anodes where the anodes in the copper sulphate are refined to 99.99% pure, thus producing a 99.99% pure cathode.
Industry uses much larger amounts of ore than in the lab. This improves the percentage yield as the more ore that is used, the more metal that can be extracted from it.
Industry uses higher temperatures than in the lab, and also the heating process does not need to be repeated as it is as efficient as need be the first time round.
Electrorefining is applied to the anodes in copper sulphate to increase the yield and make the resulting metal 99.99% pure.
The costs of extracting the copper are much much higher in industry than in the lab as the amounts needed to be extracted are of a much higher level.
Also the purity and quality of copper produced is of a higher standard, and because it is produced in bulk; expensive machinery and equipment is needed to hold and process the ore through many different stages. Large factories need to be built, and it may cost a large sum of money if pollution from the production of copper is trying to be minimalised.
Reduction of Metal Oxides
In industry, metals such as copper can be extracted. If the reactive metals are less reactive than carbon, they can be extracted through a process involving heating and the addition of coke or coal; Iron is produced in this way – as well as copper. Metals like gold and silver, often produced in industry for the making of jewellery, are so unreactive that they cannot be extracted in this way.
Metals that can be extracted in this way include: copper, lead, tin, iron and zinc.
Similarities between the lab and industrial method of extracting copper are:
- A heating process
- An extraction process
- A cooling process
- A process in which the unwanted substances are poured off.
Differences include:
- Industry use much larger scales of production
- Much more technical and expensive equipment is used in industry
- The purity and yield of metal (copper) produced in industry is higher than that of in the lab
- In industry environmental effects have to be considered so as not to cause too much damage to the atmosphere and surrounding areas of living through the production of copper
- In industry, on occasions excess metals are produced in the production of another metal, e.g. iron is produced while producing copper – the iron is removed as slag
- There are far more stages of the production of copper in industry, for example the copper ore must be crushed up into small pieces so as it is easier to work with.
- In the lab additional carbon is added to the mixture, whereas it is not in industry.
Extraction of Copper by Electrolysis
In industry, copper can also be extracted through the use of electrolysis.
Electrolysis is one way which in industry, metals are manufactured. Some of the metals that can be manufactured in this way are copper, aluminium and sodium through the electrolysis of their compounds.
Metals that are more reactive than carbon and carbon monoxide, usually have to be extracted through electrolysis, whereas metals that are less reactive than carbon/carbon monoxide can be extracted through the use or carbon through a displacement reaction.
Copper can sometimes be classed as a “native” metal which means it is found and has not been mixed with any other elements and does not need processing.
An example of electrolysis is the manufacturing of aluminium:
Aluminium oxide, known as bauxite is melted down before being reduced electrolytically to give us aluminium.
Method of Extraction Used in Industry
Electrolysis works by using electrical energy to cause chemical changes to occur at what we call the anode and cathode electrodes – the electrolyte connections.
An electrolyte consists of a solution of ions which carries the electric charge.
Electrolysis can also be used on scrap copper, this is a way of recycling, purifying, and not wasting natural resources – at cheaper prices.
In industry, electrolysis is a very expensive process which consists of many steps:-
Firstly, the metal is dissolved inside carbon lined pots/vessels containing molten cryolite.
The ore or compound must be molten or dissolved in a solution in an electrolysis cell to allow free movement of ions (electrical current).
Secondly, electrons arrive at the battery which has positively charged anodes running through it.
The now positively charged ions move towards the negative cathode, where the electrons and ions react to form molten metal.
Thirdly, the metal is now tapped or siphoned from the bottom of the pot.
Here, both an oxidation, and reduction process has happened.
End of process.
Electrolysis can also be used to purify less reactive metals – e.g. copper and zinc - that have been previously extracted using carbon or hydrogen.
Another way in which electrolysis can be used is to plate one metal with another.
Electrolysis is often a lot more expensive than extracting metal from an ore through the use of coke produced from cheap coal, as the electricity bill for the electrolysis of a metal is very high.
Sometimes, more reactive metals such as aluminium cost more to extract than less reactive metals like iron.
This being said, as copper is a lot less reactive than both carbon and iron it should be quite an expensive metal to extract
Extracting Copper through Electrolysis:
- After smelting, impure copper is poured into a block to form the positive anode. Previously purified copper is used to make the negative cathode. Both the anode and cathode are dipped into an electrolyte of copper sulphate solution.
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An electrical current passes through the solution, causing electrolysis to happen – this, forming blue copper ions (Cu2+).
- Now that we have gained positive ions, they become attracted to the negative cathode and react to form copper atoms. The mass of copper dissolving at the anode and the copper deposited on the cathode are equal – the concentration of the copper sulphate is constant.
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Impurities found in the impure copper anode decline to the bottom of the copper electrolysis vessel, where it is poured off as waste, though sometimes can be valuable and contains other metals such as silver.