The Enthalpy Change of the Thermal Decomposition of Calcium Carbonate
Results:
For CaCO3: T1 = 17
T2 = 19
DT= 02
using 2.57g of CaCO3
For CaO: T1 = 18
T2 = 27
DT= 09
using 1.39g of CaO
Analysis:
In order to determine the enthalpy change for the thermal
decomposition of calcium carbonate, we must work out the enthalpy
changes for both the reactions of calcium carbonate and calcium oxide
with hydrochloric acid.
For CaCO3:
Temperature change = 2ºC
To find the enthalpy change of a reaction, we must first work out the
amount of energy taken in by the reaction. This is done by using the
following formula:
E=DT x mass surroundings x specific heat capacity of surroundings
For this calculation, we will assume that the specific heat capacity
of HCl is identical to that of water, and that the shc of water is
4.2J/ºC/g. We used 51cm3 of HCl, so the mass of this is taken to be
51g, as 1cm3 of water weighs 1g (and we are assuming that HCl(aq) has
the same density as water). So, putting this data into the equation,
we get:
E= (-2) x 51 x 4.2
= -428.4J
Then, in order to find the enthalpy change for this reaction, this
value should be converted into kJ, and divided by the number of moles
of the substance (in this case, calcium carbonate). To find the number
of moles used, we divide the mass used by the relative atomic mass of
the substance. So, we get:
No moles = Mass ¸Mr
= 2.57 ¸100.08
= 0.026 mol.
Then we convert our energy into kJ rather than joules, getting 0.4284
kJ, and dividing this by the amount of substance we used. So, this
comes out as:
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...sregarded.
These problems were not the only ones with the experiment - the major
factor being that it was only performed once, with no repeats - these
values were taken to be correct, with no comparisons made. This could
easily be rectified by performing a suitable number of repetitions -
for example, 4 repetitions could be made, and an average taken. This
would vastly improve the reliability of the end results, as the
average would more accurately reflect the true temperature change.
Overall, there were a large number of problems with this experiment,
and correspondingly, there are a large number of things that I would
like to change if I were to be able to repeat this experiment. The
experiment was successful I that results were obtained, but I suspect
that these results are vastly different to the actual values.
There were no significant error factors that may have affected the arrangement of the lab experiment. Everything went smoothly with relative ease.
We began this investigation by suiting up in lab aprons and goggles, we then gathered our materials, found a lab station and got to work. We decided to start with the magnesium in hydrochloric acid first, we measured out 198.5 L of HCl and put it in the foam-cup calorimeter and took initial temperature reading. We then selected a piece of magnesium ribbon and found its mass: 0.01g. This piece was placed in the calorimeter and the lid was shut immediately to prevent heat from escaping. We “swirled” the liquid mixture in the calorimeter to ensure a reaction, and waited for a temperature change. After a few moments, the final temperature was recorded and DT determined.
Okay, if our lithium weight is going to be 6.941 g/moL Then that means we have to take 24.6g of Lithium and multiply it by 1 mol of Lithium over 6.941 g of Lithium. This would equal to be 3.544 mol of Lithium. Then we have to take that 3.544 and multiply it by 1 mol of hydrogen gas over 2 mol of lithium. Which would then equal into 1.772 mol of hydrogen gas. We can then figure out that 1.772 is our “n”. The “T” is our 301 Kelvin, the “P” is our 1.01 atm and the “R” is our 0.0820 which would be the L atm over mol k. And we can’t forget about our “V” which would be V equals nRT over P which equals 1.772 mol divided by 0.0820 L atm over mol kelvin multiplied by 301 kelvin over 1.01 atm which equals to our final answer of: 43.33 of H2
Discussion: The percent of errors is 59.62%. Several errors could have happened during the experiment. Weak techniques may occur.
Text Box: CaCO3 + HCl = CaCl2 + CO2 + H2O calcium carbonate + hydrochloric acid = calcium chloride + carbon dioxide + water
* Note the mass down in the table at the end of the first page.
Specific heat capacity of aqueous solution (taken as water = 4.18 J.g-1.K-1). T = Temperature change (oK). We can thus determine the enthalpy changes of reaction 1 and reaction 2 using the mean (14) of the data obtained. Reaction 1: H = 50 x 4.18 x -2.12.
Tf-Ti). Next, subtract the initial temperature, 25 degrees from the final temperature, 29 degrees putting the change in temperature at 4 °C. To calculate the heat absorbed by the water in calorimeter, use the formula (q = mCΔT). Plug in 50 mL for (m), 4.184 J for (C) and 4 °C for the initial temperature (ΔT), then multiply.
One possible source of experimental error could be not having a solid measurement of magnesium hydroxide nor citric acid. This is because we were told to measure out between 5.6g-5.8g for magnesium hydroxide and 14g-21g for citric acid. If accuracy measures how closely a measured value is to the accepted value and or true value, then accuracy may not have been an aspect that was achieved in this lab. Therefore, not having a solid precise measurement and accurate measurement was another source of experimental error.
There is also the potential of human error within this experiment for example finding the meniscus is important to get an accurate amount using the graduated pipettes and burettes. There is a possibility that at one point in the experiment a chemical was measured inaccurately affecting the results. To resolve this, the experiment should have been repeated three times.
Possible sources of error in this experiment include the inaccuracy of measurements, as correct measurements are vital for the experiment.
Rate of Reaction Between Calcium Carbonate and Hydrochloric Acid Plan: In my experiment I will measure the rate of reaction between calcium carbonate and hydrochloric acid. The rate of the reaction is the speed that the reaction takes place so by measuring the rate I will measure the amount of time the reaction takes. Hydrochloric acid is a strong acid that is found in digestive juices in the stomach, it is also used for cleaning metals before they are coated. Calcium carbonate has a few forms including chalk and limestone the main use of these two materials is in the making of concrete, which is used for many things such as buildings. When you put calcium carbonate and hydrochloric acid together they react to form calcium chloride, carbon dioxide and water.
Moles Volume HCl Volume Water 2 M 10 cm 3 0 cm 3 1.5 M 7.5 cm 3 2.5 cm 3 1 M 5 cm 3 5 cm 3 0.5 M 2.5 cm 3 7.5 cm 3
The Effect of Temperature on the Rate of Reaction Between Hydrochloric Acid and Calcium Carbonate
is 40.c but his is a chemical enzyme so it will work best a little