Methods-
1) Set up the apparatus as shown above.
2) Weight the mass of 0.2 g of CuCO3 to the nearest 0.01 gram directly in the test tube.
The reason that I have used 0.2g of CuCO3 is because it produces 0.2/123.5 = 0.001619 mol 24000* 0.001619mol = 38.86 cm3 of CO2 which is lower than the volume of the graduated cylinder. And this will allow as to measure the
3) Fill a 50-ml measuring cylinder with water to the top, cover, invert, lower into a filled pneumatic trough, and uncover beneath the water surface.
4) Place the stopper with the delivery tube (plastic tube) into the test tube. Place delivery tube into the inverted graduated cylinder. Heat the copper (II) carbonate slowly and uniformly over a laboratory burner.
5) Then we will see bubbles collecting in the measuring cylinder, the rate of
CO2 release will begin to slow down when decomposition is near completion. When the bubbling stops, remove the heat and the delivery tube at the same time.
6) The measuring Cylinder is held perpendicular in the water and read the bottom of the meniscus to determine the amount of water displaced by the gas.
7) The temperature of water is recorded (which will be the same as gas temperature) and the barometric reading is obtained.
Further information about the method?
1) This experiment requires measuring the temperature inside the boiling tube, which is difficult using standard laboratory equipment.
2) Instead a "control" experiment could be set up, in which no copper carbonate is used, but an empty boiling tube is heated for the same length of time, and the volume of the gas collected due to expansion of the air measured. This volume could then be subtracted from the volume obtained by the decomposition of the copper carbonate to give a more accurate result for the volume of gas given off.
3) It will be necessary to keep the size of the boiling tube constant because the extra volume given out by the expansion of the hot air will be different depending on the size of the test tube.
4) We should Use the same boiling tube and bung for each repeat.
Calculations of results:
1. Write the balanced chemical equation for the decomposition of copper (II) carbonate.
2. Using Dalton's Law of Partial Pressures, determine the pressure of the carbon dioxide gas.
3. using mass to mole stoichiometry, determine the moles of carbon dioxide expected from this reaction.
4. using the Ideal Gas Equation, determine the theoretical volume of carbon dioxide expected.
5. Do a percentage error calculation for the volume of carbon dioxide gas.
6. using the combined gas law, determine the volume of carbon dioxide gas generated at STP.
7. Find the moles of copper (II) carbonate used-, use this value and the volume of carbon dioxide gas at STP to determine the volume of carbon dioxide gas per mole at STP.
8. Then say which equation is right. Which method is more likely to give a more accurate result - measuring the volume or the mass of the gas?
Important information before the experiment.
- The data table should be constructed before the trials are run
- 2 or 3 trials should be run and to contain accurate observations compare data for the entire class.
- The gas delivery tube is constructed from the pulled stem of a Beral pipet. A length of 20-25 cm is sufficient. Push an unpulled end into the hole of a 00 stopper.
- If there is a problem with leakage of the emerging gas, use of sealant materials at the junction between the gas tube and the rubber stopper seems to help.
- The gas delivery tube should be removed as soon as bubbles stop from under the water. If not, as the gases cool, water may be sucked back into the tube causing it to break
Equipment:
Pneumatic trough or large beaker
test tube (13 x 100 mm)
1 hole stopper to fit test tube (00)
plastic tube (from pulled Beral)
graduated cylinder (25-mL or 50-mL)
thermometer
laboratory burner
test tube clamp
CuCO3 (solid)
mass balance
Health and safety
- Every chemical is a potential hazard to health, the degree of risk depending on its physical and chemical properties and the kind of exposure. We should make sure that we know how to dispose of waste and how to deal with spillages immediate clearing of spillages of any kind, wet or dry.
∙ any splashes into the eye must be washed out continuously for 10-15 minutes
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Before starting the experiment we must make sure to wear safety goggles and an apron in the lab at all times. Do not ingest chemicals. Use caution around open flames.
Finnal Calculations:
Equation 1: 2CuCO3(s) ------> Cu2O(s) + 2CO2g) + 1/2O2
As i have used 0.2g of CuCO3 I have to find its amount of moles by the formula of
So 0.2/123.5 = 0.001619 mol
If CuCO3 is 0.001619 mol then 2CO2 is 0.001619 mol as well.
Then to get the volume of gas we multiply 0.001619 moles with 24000 which we get 38.86 cm3,
If CuCO3 is 0.001619 mol then ½ O2 is 1/2 * 0.001619 / 2 = 0.000405 moles.
0.000405 moles * 24000 = 9.72 cm3
2CO2 (38.86 cm3) + ½ O2 (9.72 cm3) = 48.58 cm3
Equation 2: CuCO3(s) --------->CuO(s) + CO2 (g)
0.2 /123.5= 0.001619mol 24000* 0.001619mol = 38.86 cm3 of CO2
If the original volume that is obtained after the experiment is performed is close to either of this two volumes then that is the correct equation,
Equation 1: = 48.58 cm3 Equation 2: = 38.86 cm3
