6.02 x 10²³ atoms, we refer to 6.02 x 10²³ atoms of an element as 1 mole.
- I will calculate a suitable mass that should be used by using the mole equations (see later on).
- This suitable mass should not produce more than 100cm³ volume of gas.
- This can then be decomposed by the heat from the Bunsen burner.
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We will continuously heat the copper carbonate until no more gas is produced. Once no more gas is produced I will know that all the CuCo3 has decomposed.
- Once there is no more gas entering the syringe and the syringe has stopped moving. I will allow the gases to cool to room temperature for about 5 – 10 minutes because when heated, gases tend to expand, which may affect my results.
- I will make the copper carbonate into powder to increase its surface area and thus increasing the rate of reaction.
- I will be able to obtain more readings in the time period so a more precise average can be produced.
Finding out the Mass of CuO to use, and the volumes of gas produced.
Equation 1 – 2CuCO3(s) Cu2O(s) + 2CO2(g) + ½O2
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If I were to use 1g of CuCO3, I can calculate the number of moles, using the formula:
Moles = Mass/R.F.M
= 1/(63.5 + 12 + (16 x 3))
= 1/123.5
= 0.008moles
- I want to find out the volume of gas in the syringe for this formula to be correct, so I must use the mole ratio and the formula for the volume of gas to work it out:
2CuCO3(s) Cu2O(s) + 2CO2(g) + ½O2
Mole ratio: 2 : 1 : 2 : 0.5
2CO2 : The ratio is the same as 2CuCO3, therefore the moles is also equal to 0.008 moles.
Volume of Gas = Moles x 24dm³
= 0.008 x 24
= 0.190dm³ or (x1000) = 190cm³
½O2 : The ration is a ¼ of the mole ratio, therefore the moles for oxygen is:
=0.008/4
= 0.002 moles
Volume of gas = Moles x 24dm³
= 0.002 x 24
= 0.048dm³ or (x1000) = 48.0cm³
- The total amount of gas in the syringe therefore would be:
190cm³ + 48.0cm³ = 238.0cm³
- This is a problem because the gas syringe cannot hold this amount of gas.
- If I were to multiply the total gas by 3/10 we would get 71.4cm³total volume of gas.
- This means that if we multiply the mass by 3/10, we would get 0.30g of copper carbonate.
- Thus, I will use 0.30g of copper carbonate, and if this value produced a volume that was less than 100cm³ in the second equation:
Equation 2 – CuCO3(s) CuO(s) + CO2(g)
Moles = Mass/R.F.M
= 0.30/(63.5 + 12 + (16 x 3))
= 0.30/123.5
= 0.00243 moles
CuCO3(s) CuO(s) + CO2(g)
Mole Ratio 1 : 1 : 1
Therefore the moles of CuO is 0.00243 moles.
Volume of Gas = Moles x 24dm³
= 0.00243 x 24
= 0.0583dm³ or (x1000) = 58.3cm³
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In conclusion, I will use 0.30g of copper carbonate and when it decomposes, if the total amount of gas produced is 71.4 cm³ then the reaction obeys equation 1, and forms Copper(II) Oxide.
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However, if 58.3cm³ of gas is produced then the reaction obeys the equation 2, and forms Copper(I) Oxide.
Accuracy of Equipment and Reagents
- All my results have been given to 3 significant figures except for the mass of copper carbonate, which is given to 2 decimal places because the scale can only measure to 2.d.p.
Graduated Gas Syringe, Mass and Range:
Equation 1 – 2CuCO3(s) Cu2O(s) + 2CO2(g) + ½O2
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This equation will produce 71.4cm³ of gas. The syringe, which collects the gas has an accuracy to the nearest decimal place, ±0.5cm³. Therefore the percentage error is:
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(±0.5/71.4) × 100 = 0.70%.
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The range of the gas syringe allows values between 71.3<cm³<71.5
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The weighing scale has an accuracy to 2 decimal places, ±0.005g. This has a percentage error of 1.67% and the scale allows values between 0.29g<g<0.31.
- The total error for equation 1 is:
- This indicates that these errors are insignificant and should not affect the results.
Equation 2 – CuCO3(s) CuO(s) + CO2(g)
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This equation will produce 58.3cm³ of gas. The syringe, which collects the gas, has an accuracy to the nearest decimal place, ±0.5cm³. The percentage error is:
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(±0.5/58.3) × 100 = 0.86%.
- The range of the syringe allows values between
58.2<cm³<58.4.
- The total error for equation 2 is:
- This indicates that these errors are insignificant and should not affect the results.
- I think that this is the least error possible, because if the copper carbonate is not pure, then we will not produce these results and the accuracy.
Precision
- To make sure that I produce accurate results, I intend to repeat the experiment several times until I achieve consistent results.
Safety
- Lab coats must be worn during the experiment.
- Goggles must be worn at all times.
- Make sure that you not using any faulty equipment.
- Make sure that the gas syringe moves smoothly and its slider does not get stuck when collecting the gas, which will increase the pressure exerted on it, causing it to break.
- Allow the experiment to cool before clearing up because if the conical flask is washed immediately then it will break and also the equipment will be very hot.
Bibliography
- “Chemistry 1” endorsed by OCR
- “AS Level Chemistry” by John Atkinson and Carol Hibbert
- “Chemistry In Context” by Graham Hill and John Holman