Determining the Number of moles of Water of Crystallisation and Hydrate formula of Zinc (II) Sulfate (ZnSO4):
Conclusion:
In conclusion, to find out the hydrate formula of any salt, the salt has to be heated until there is no further weight loss. This is so because when determining the hydrate formula, you have to find the total mass of the hydrated salt in the crucible with the lid, the total mass of the salt in the crucible with the lid after it has been heated until no further weight loss, the mass of the crucible with lid, and the mass of the dehydrated salt. These masses has to be the 4 variables used to determine the hydrate formula, because if there is no further weight loss then all the water in the hydrated salt has been evaporated. If you got results that showed the mass decreasing every time you heated the salt for 5 extra minutes, then this means that the water in the salt hasn’t completely been evaporated and the hydrate formula is going to turn out to be wrong. This is the reason my 4 variables to determine the hydrate formula was the total mass of the hydrated Zinc(II) Sulfate (ZnSO4) salt in the crucible with the lid, the mass of the Zinc(II) Sulfate (ZnSO4) salt in the crucible with the lid after the fourth time it has been heated (because this is the maximum times I could have heated it because of our teacher’s orders), mass of the crucible with the lid, and the mass of the dehydrated Zinc(II) Sulfate (ZnSO4) salt. These 4 variables helped me to determine the formula of the Zinc (II) Sulfate (ZnSO4) salt’s hydrate, which was Zinc (II) Sulfate Heptahydrate (ZnSO4·7H2O). Therefore to find out the hydrate of any salt with high precision/accuracy is to use these 4 variables, and to make sure that the mass does not decrease in weight further.
Evaluation:
This lab experiment had several mistakes that were identified as I was able to figure out the hydrate formula, and as I related it to other experiments in the internet. One of the major mistakes I made was that I forgot to calculate for the mass of the dehydrated Zinc (II) Sulfate (ZnSO4). The first time I tried calculating for the mass of the dehydrated Zinc (II) Sulfate (ZnSO4), I accidently added it’s mass with the mass of the crucible with the lid. This gave me the mass of the dehydrated Zinc (II) Sulfate (ZnSO4) with the crucible and the lid. So my answer in the end for the hydrate turned out to be in decimals. My ratio for the hydrate to the dehydrated Zinc (II) Sulfate (ZnSO4) became 0.66:1. Then I realized that hydrates can’t be in decimals, and as I scanned the data chart again and again I found out that I forgot to minus the mass of the crucible with the lid from the mass of the Zinc (II) Sulfate (ZnSO4) salt in the crucible with the lid. Only by doing this will I get the true mass of the hydrated Zinc (II) Sulfate (ZnSO4) salt. Then by taking away the mass of water lost from the mass of the hydrated Zinc(II) Sulfate (ZnSO4) salt, I will be left with the dehydrated Zinc(II) Sulfate (ZnSO4) salt (which means just the salt without any water). In the end I finally ended up with the ratio of 7:1 of hydrates to dehydrated Zinc (II) Sulfate (ZnSO4) salt. I rechecked with my peers, books and internet sources, and in the end I concluded with the formula of Zinc (II) Sulfate Heptahydrate (ZnSO4·7H2O). I believe that the solution for this problem is to analyze the data more clearly and then do the lab. The next problem was that in the calculations if I didn’t round the moles, my answer for the hydrate ratio would have been 6.85:1 for hydrate to Zinc (II) Sulfate (ZnSO4). I presume that if I was given an additional 15-20 minutes for an extra heating, I could of gotten exactly 7 as my hydrate without the rounding of both the moles of water lost (H2O lost), and the rounding of the moles of the dehydrated Zinc(II) Sulfate (ZnSO4). All in all this lab is like a precursor to the creation of amazing future labs, and by learning to identify the different ways you can make mistakes in a lab, the future labs will be better than the rest.
A picture of a plate full of Zinc (II) Sulfate (ZnSO4) salts. It is a colorless crystalline, water soluble chemical compound.
A picture of Zinc (II) Sulfate Heptahydrate (ZnSO4·7H2O), which is also called the mineral goslarite (also known as the white vitrol). It is transparent to translucent and ranges from colorless, green, blue, or brown. It forms acicular crystals, stalactitic forms and massive clumps.
