Assessed Practical (Skill P)
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Introduction
AS - Assessed Practical (Skill P) The aim of this experiment is to find out which reaction is correct for the thermal decomposition of copper carbonate out of the following two equations. 2CuCO3(s) ==> Cu2O(s) + 2CO2(g) + 1/2O2(g) CuCO3(s) ==> CuO(s) + CO2(g) Avagadro's constant states that one mole of gas under standard conditions will fill 24dm3 under standard conditions so it is possible to find the amount of gas evolved by measuring the volume. From this it is also possible to find which version of the reaction has taken place. How much copper carbonate should be used? The first equation will produce more gas so that is the maximum amount to be taken into account when deciding how much copper carbonate needs to be used. If one mole of copper carbonate is used then one mole of CO2 and 0.25 moles of O2 will be evolved. ...read more.
Middle
Gas syringe (100cm3) Rubber tubing and bung Copper carbonate Safety Because a Bunsen burner is being used certain precautions need to be taken whilst carrying out the experiment. When a Bunsen burner is turned on it should be with the safety flame, in order to make everyone close by aware that the Bunsen burner is turned on. The apparatus should not be handled straight after heating or it will cause burns. Copper carbonate is an irritant to the eyes so eye protection should be worn throughout the experiment, to protect the eyes from the Bunsen burner flame and the copper carbonate. Copper carbonate should not be swallowed, and is irritant.1 Copper (II) oxide (CuO) is also irritant and should not be ingested or allowed near the eyes.2 Likewise, copper (I) oxide (Cu2O) should not be ingested.3 Conditions The experiment must be carried out under standard conditions - 1 atmosphere of pressure and a temperature of 298K4. ...read more.
Conclusion
* Observe the volume of gas using the gas syringe. * Repeat the experiment 3 times. For each experiment use a new conical flask and reset the gas syringe. Calculations If the equation "2CuCO3(s) ==> Cu2O(s) + 2CO2(g) + 1/2O2(g)" is correct, the amount of gas evolved should be around 61 cm3 using the calculation, (M / Mr) x 30000 This is because for each mole of copper carbonate that reacts 30000 cm3 gas is evolved. (0.25 / 123.664) x 30000 = 60.648 For the equation "CuCO3(s) ==> CuO(s) + CO2(g)" there is only 24000 cm3 gas evolved per mole of copper carbonate that reacts, so the formula for finding the volume is, (M / Mr) x 24000 (0.25 / 123.664) x 24000 = 48.519 Therefore if this equation is correct approximately 49 cm3 gas is evolved. 1 http://en.wikipedia.org/wiki/copper_carbonate 2 http://en.wikipedia.org/wiki/Copper(II)_oxide 3 http://ptcl.chem.ox.ac.uk/MSDS/CU/cuprous_oxide.html 4 Chemistry 1 - Cambridge. ?? ?? ?? ?? George Noble 12JK ...read more.
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Here's what a star student thought of this essay
Response to the question
The response to the question was done well, but the candidate had a tendency to favour one equation over the other in examining the moles of gas produced, and explained this without explaining the theory behind the other one most ...
Read full reviewResponse to the question
The response to the question was done well, but the candidate had a tendency to favour one equation over the other in examining the moles of gas produced, and explained this without explaining the theory behind the other one most of the time, so the candidate should revise their work to give a balanced view. The piece of work needs finishing.
Level of analysis
The introduction is good, the equations used are correct. The candidate does not explain clearly why Avagadros constant means that we will know which substance is made which should have been explained a bit clearer. The theory behind the experiment is explained well, but the calculations and thinking behind their statements should be labelled more clearly as they tend to jump with assumptions that the person reading understand where they have for example got the 30 decimetres from with the first equation. The gas syringe part is also not explained clearly. The conditions for the experiment are explained well. The results and calculations are not finished, but to their stage they are correct.
Quality of writing
Spelling, grammar, and punctuation are all done to a good standard. The layout of the text is also done well with clear subheadings and laid out calculations.
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Reviewed by skatealexia 27/07/2012
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