Practical investigations
Read our general notes on Risk Assessment
Investigating the decomposition of copper carbonate
This advice is a response to the questions we have received about this investigation over the last year. It is not our job to do your investigation for you but we can offer some advice and give hints.
Please note that if you are following the Nuffield course this investigation is suitable for practice but not for an investigation submitted as A2 coursework. In the Nuffield course the A2 investigation must relate to the content of the A2 topics in the specification.
WHAT IS COPPER CARBONATE?
You must consult text books and other sources of information such as the internet to find out the chemical nature of copper carbonate? Look at the catalogues of suppliers of chemicals, or the labels on the reagent bottles. Some metal compounds are not simple carbonates but are, so-called, basic carbonates.
Copper can exist in two main oxidation states. What is the oxidation state of copper in copper carbonate?
Is copper carbonate in the laboratory chemically the same as the mineral malachite?
Make a careful note of all the sources you consult (including the URLs of web sites) so that you can list the references in your report. This is important.
HEATING COPPER CARBONATE
Once you know the formula of the compound consider the possible simpler compounds and elements that might form when it decomposes. Look in textbooks to see what normally happens when metal carbonates decompose. Is it likely that the copper will change oxidation state?
QUALITATIVE TESTS
Once you know what you might be looking for try some familiar chemical tests to see if you can decide on the main products of heating copper carbonate.
What is the solid residue – is it copper or one of the two possible oxides? How could you tell?
How many gases or vapours are formed? If there are two can you detect them both – and if so - how?
QUANTITATIVE INVESTIGATIONS
What are the possible and likely equations for the decomposition of copper carbonate?
Your equations will show that the mass of solid residue will be less than the mass of copper carbonate you started with. How can you check, by experiment, that the copper carbonate has completely decomposed? What precautions are needed when weighing a solid formed by thermal decomposition? How can you see, by calculation, whether the the change in mass corresponds to one or other of your possible equations?
You can calculate from your equations the volumes of the gaseous products from a given mass of copper carbonate knowing that 1 mol of any gas has a volume of 24 000 cm3 at room temperature (around 20 °C). You can predict the volume of gas(es) expected from a certain mass of copper carbonate.
Are any of the gases likely to condense at room temperature? If so, how will you allow for this? What effect is this likely to have on the measurements you take on other gases?
Instead of measuring the volume of gases formed you could consider passing the gas through a U-tube containing a chemical to absorb the gas or gases, then the increase in mass of the U-tube and its contents is equal to the mass of gas(es) absorbed. If the gas is acidic, then consider absorbing it in a solid alkali (but not one that absorbs water from the air fast). Again you can compare your results with your predictions from possible equations.
Which method is more likely to give a more accurate result – measuring the volume or the mass of the gas(es)?
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Lila
Hey guys this page is great. If it gave us the answers it would be cheating. It Kinda tells you what you are after just by giving the questions.
13 November 2005
Mike
The reason I'm looking on sites like this is because I can't find the answers in textbooks or guides. I did however, find a few more things I never considered researching for this coursework.
05 May 2005
Emma
This was really useful as it provided a rough guideline of what I should be thinking of for my coursework. Thank you very much
27 April 2005
Lucy
The questions were interesting and helped me think of things to include in my investigation. However, I could do with some answers!
19 March 2005
SOS
I'ts all he stuff I was after for my assignment
:)
19 February 2005
Chem Student
I was hoping for a little more, if I had the answers I wouldn't be on the net looking for them!!!
21 January 2005
Anonymous
25 April 2004
vernon
We're meant to ask the questions to help us learn, whereas you are just continously asking questions for us that we can't find out because they're not in our textbooks.
31 March 2004
updated: 15 October 2003
