Analysis
- Use the evidence obtained to calculate the mass of hydrate that you used.
Trial 1:
Trial 2:
- Calculate the mass of water of hydration lost and the mass of the dehydrated salt remaining.
To calculate mass of water of hydration lost:
Trial 1:
Trial 2:
To calculate the mass of the dehydrated salt remaining:
Trial 1:
Trial 2:
- Determine the amount in moles of the water of hydration and the amount in moles of the dehydrated salt.
The amount in moles of the water of hydration:
The amount in moles of the dehydrate salt:
- Determine the formula of the hydrate.
CuSO4 • xH2O(s)
In order to find x the bigger number has to be divided by the smallest number. Also the percentage uncertainty has to be calculated too:
Trial 1:
Trial 2:
Trial 1:
Trial 1:
Therefore, in Trial 1 and in Trial 2 . Therefore, the two solutions for Trial 1 are 4.96 and 4.98 and the two solutions for Trial 2 are 4.92 and4.94. The formula has to be written as a whole digit, and so 5 is the solution when all four solutions are rounded.
Evaluation
- What was the purpose of heating the empty crucible and lid in step 1?
The purpose of heating the empty crucible and lid in step 1 is to makes sure nothing is wrong with the crucible and the lid. It should not be cracked. Another reason was to burn off all the unwanted products. We don’t want hydrate copper (II) sulphate reacting with other components which will increases the result error.
- Why were the crucible and contents heated until the mass remained constant?
The purpose of heating the crucible and lid for many times until the mass remained constant was because to lessen all the unwanted products which would by reducing the error. When finding a formula, it is important to right all the values as the way they are. If I would have got 4.5g instead of 4.9g, I would multiple everything by two and making the whole equation wrong. So, it is crucial to be as accurate as possible.
- Reference a reliable source to find the literature value for the chemical formula of copper (II) sulphate hydrate. How does your formula compare to this value?
The formula the website showed was CuSO4•5H2O. I used two website to make sure that I have the relevant information. My formula matches with this formula very well. This suggest that during the lab, minimum error were made.
- What is the uncertainty in your calculated result? Does your calculated formula fall within the range of your uncertainty?
The uncertainty in my calculated result is 0.01. My uncertainty is very small and the solution I got in Trial 1 is 4.94 and in Trial 2 is 4.93. The uncertainty is small and that’s why the solution, when we will round up will be 5. This is why my calculated formula falls within the range of the my uncertainty.
