moles of gas.= 8.1 x 10-4 x 1.25
moles of gas = 0.00101 moles
I Shall now use the ideal gas equation to calculate the gas produced to actual room temperature and pressure.
The Ideal Gas Law (General gas equation):
PV = nRT
Where
P=pressure
V=volume
n=moles of gas
T=temperature
R = 8.314J K-1 mol-1
For P is shall use standard pressure which is 1 atmosphere = 103kpa
For T I shall use a standard 20oC which is 293K
Moles = 0.00101
Calculating Volume of Gas: V = (nRT) ÷ P
Volume of gas = (0.00101x8.314x293) / 103
Volume of gas = 0.02388 dm3 = 23.9cm3(3.s.f)
Equation 2:
I shall now calculate the expected gas to be given off if equation 2 is correct.
Using 0.1 grams of copper carbonate:
Moles of copper carbonate used = mass / relative molecular mass
Mass = 0.1 grams
R.M.M of copper carbonate = 63.5 + 12 + (16 x 3) = 123.5 grams
Moles = 0.1 / 123.5 = 8.1 x 10-4
If we now compare the moles of copper carbonate to the moles of gas (carbon dioxide) given off with find that the molar ratio of the equation is 1:1.
As the equation is a 1:1 equation then the moles of gas are the same as the moles of carbon carbonate.
8.1 x 10-4 = moles of gas.
I Shall now again use the ideal gas equation to calculate the gas produced to actual room temperature and pressure.
The Ideal Gas Law (General gas equation):
PV = nRT
As before I shall use:
For P is shall use standard pressure which is 1 atmosphere = 103kpa
For T I shall use a standard 20oC which is 293K
Moles = 8.1 x 10-4 moles
Calculating Volume of Gas: V = (nRT) ÷ P
Volume of gas = (8.1 x 10-4 x8.314x293) / 103
Volume of gas = 0.0191dm3 = 19.1cm3 (3.s.f)
My two expected volumes of gas are 19.1 cm3 and 23.9 cm3, These are small enough for me to be able to use the more accurate, syringe, method of collecting gas, this should make my experiment more accurate.
Equipment list
Heat mat
Clamp stand
100ml gas syringe
Conical flask
Bunsen burner
Tripod
Tube/hose with bung attachment
Top-pan balance
Gauze
Lime water
Diagram :
Method
- Attach the gas syringe to the clamp stand making sure it is parallel to the bench as shown in the diagram. Press on the end of the gas syringe until the gas syringe reads 0ml of gas.
- Place the tripod on a heat mat and then place the gauze on top of the tripod then place the conical flask at the top as shown in diagram.
- Place the bung from one end of the tube onto the top of the conical flask and attach the other end to the gas syringe.
- Weight 0.1 grams of copper carbonate on the top-pan balance.
- Remove bung from the conical flask and place the copper carbonate into the flask and replace the bung.
- When the bung is secure heat the copper carbonate on a blue flame until no more gas is been released.
-
Wait 20 minutes until the gas has returned to room temperature as when it is hot it will expand and take up more volume. So to acquire a correct volume of gas we must wait for it too return to room temperature, approx 20oC, so that the volume is correct for a temperature of 20oC, the values I used in my ideal gas equations.
- After 20 minutes record volume of gas.
Remember as we are using a Bunsen burner to wear goggle and a safety apron at all time and leave Bunsen burner on a safety flame when not in use
Compare the recorded gas produced to out theoretical values.
Expected gas produced for equation 1= 23.9 cm3
If the gas given off was between 23.00 – 25.00cm3 then equation 1 was the correct equation for the decomposition of copper carbonate.
Expected gas produced for equation 2 = 19.1 cm3
If the gas given off was between 18.00 – 20.00 cm3 then equation 2 was the correct equation for the decomposing of copper carbonate.
Additional tests to prove which equation is correct.
Lime water – is you bubble through the gas collected through lime water, it should turn milky if carbon dioxide is present. As both equations produce carbon dioxide, no matter what happen the lime water should go milky.
Splint test – this is the important test as it tests for the presence of oxygen and this is what divides the 2 equations, the first producing oxygen and the second not. If you try and relight a flint after it has been put out, it will relight if it is provided oxygen, so if the splint relights this gives further evidence equation 1 is correct.
Information used on this plan was from:
Chemistry 1 textbook
