The sample needed to return to the oven for a second heating to insure that all of the water was heated off of the sample. If the mass difference between the first and second heating was greater than 0. 005g, the sample would have been needed to be heated a third time because all of the water had not yet been heated off. Sample calculations: Mass of the sample: Heating mass difference: Molar mass of CuC12: Moles of the anhydrous sample: Mass % of H20: % Absolute error: of hydrate recovered: Conclusion The hydration number of water was found using the ratio of CuC12 moles and H20 moles.
The ratio was found to be 2 moles of H20 for every 1 mole of CuC12. A new chemical equation of could be written using this stoichiometric ratio. The actual hydration number also is 2 moles of H20. The calculated absolute percent error was found to be zero since the calculated hydration number was the same as the actual hydration number. It was also found that some of the rehydrated sample could not be recovered because some of the rehydrated sample remained tuck to the filter paper and was unable to be measured in the mass of the rehydrated sample.
This did not allow the full sample to be recovered. Questions 1 . The experimental hydration number resulted in being 2. The true hydration number is also 2. When % absolute error was calculated, the result was 0% error. Since the experiment concluded with no percent error, which means no error, there are no possible sources of error for the experiment. 2. Three significant figures were used to report the amount of anhydrate in moles and the amount of water released in moles.
The way to determine the significant figures in this calculation was to look at the experimental value in the two equations, which is the mass. The mass had 3 significant fgures and the answer must have the 3. When the anhydrous sample was rehydrated, only 93. 4% of the sample could be recovered. This was because some of the mass of the sample remained stuck to the filter paper and could not be measured in the final mass calculation. This automatically resulted in less mass and did not allow for 100% of the mass to be recovered. 4.
If the hydrate would have been overheated and had released a gas, there would have been excess mass released because the mass of the gas that would have been released and water released combined would have been greater than the mass of just the water released. The way to know if that had happened would have been if the mass of the water released would be over 2. 5. I believe that with a Bunsen burner to dry would have provided more accurate results for the hydration number because the heat can be applied more directly and the time to heat would be faster, giving less room for error in the data.