In order to identify the unknown substance, it was necessary to research the known ratios of all four choices and then compare the calculated ratio for each of the four to that of the unknown. Furthermore, the strength of the heat had to be changed once from low to high as there was only 15 minutes total to heat the substance. Other group’s reaction did not seem to cause some of their data to get lost. Also, some of the hydrate popped out from the beaker due to the heating. This indicated that more water evaporated progressively and the sizes of the particles decreased accordingly. It seemed as if the particles were partially melting. As the hydrate was heated with a bunsen burner, the consistency of the substance changed from being crystal-like to chalk-like.

The substance looked similar to table salt as the particles were clearly visible. The hydrate (A) was white and crystal-like at the beginning. (mass of beaker+anhydrate) - (mass of beaker) (mass of beaker+hydrate) - (mass of beaker) Thus, the ratio between water and magnesium sulfate will be close to being 7:1. This hydrate was previously mentioned in class to be magnesium sulfate heptahydrate. Once we know how much water is needed for each magnesium sulfate, we can then name the substance in MgSO 4 x H 2 O, where x represents the ratio. The ratios between molecules are in integers, but as this is an experiment, it will be more likely to acquire the ratio in decimal points. Once the numbers of moles of two substances are known, the ratio can be computed by dividing them. The number of water moles can also be known by repeating the same procedure, but with the molar mass of water instead. By multiplying the mass of the anhydrate, which is magnesium sulfate in the experiment, with its molar mass, the number of moles present at the end can be determined. We believe our hydrate was magnesium sulfate, because the unknown hydrate was more closely related in physical appearance to that of magnesium sulfate, compared to the the three other options.įurthermore, in order to determine the exact name of the hydrate, we must find out the ratio between the anhydrate and water that are associated with the hydrate. Magnesium sulfate, the only left option, is white in appearance which makes it a possible identification for our hydrate.

This means we can exclude these three options from our prediction. Iron (III) sulfate has a purple tint to it, and has a crystalline structure.

Iron (III) chloride usually has a bright yellow appearance. Since copper (II) sulfate is usually a bright blue due to Cu 2+ presence, we can exclude that option from our prediction. Observing our nitrate, it has a white crystalline structure, representing that similar to table salt. Testable Prediction: Our unknown hydrate may be a hydrate of copper(II) sulfate, magnesium sulfate, iron(III) chloride, or iron(III) nitrate. Experimental Question: How can we experimentally determine the formula of an unknown hydrate, A?

Chemlab hydrate formula