Sample Lab Report - Epsom Salt

Epsom salt, found at Epsom, England, has the formula of . We expelled the seven waters of hydration by exposing the hydrate to intense heat. We used two different batches of salt, one provided by the laboratory supervisor, one provided by the instructor. The first was determined to be at 95% confidence level. The other was determined to be 50.9% which is close to the true value of 51.2%. We concluded that the salt from the stockroom has been exposed to the dry atmosphere of Idaho, and perhaps has lost some water from its crystal lattice. The salt provided by the instructor, on the other hand, was freshly bought in a sealed container. Therefore our final determination of waters of crystallization in Epsom salt is 50.9%

INTRODUCTION

Epsom salt ( ) was originally found at Epsom in England around the 17th century. This chemical compound contains seven waters of hydration: waters that are trapped inside the crystalline lattice of . In fact, the waters are so tightly bound to the lattice that magnesium sulfate heptahydrate is a compound altogether different from the anhydrous magnesium sulfate. In this experiment we used gravimetric analysis and intense heat to rid Epsom salt of the water according to the equation 1:

Equation 1

We then used equation 2 to calculate the percentage of water by weight in Epsom salt

Equation 2

We compared our results with the true value of 51.16%

MATERIALS & METHODS

Apparatus. We utilized crucibles, crucible lids, clay triangle and the technique of bending down the edges of the triangle. This setup allowed us to expose Epsom salt to high heat in a vessel designed for high temperature exposure.

Reagents. We used a small carton of Epsom salt provided by the stockroom and a large blue bag of Epsom salt provided by the instructor.

Safety Considerations. Cold crucibles look the same as hot ones. We heated the hydrate gently at first because the water formed can sputter.

Procedures. At first we dried the crucible in the flame three times and let it come to a constant mass by measuring the weight each time. To determine percentage of water in Epsom salt, we measured about 2g of the salt into three different, dried crucibles. The crucibles were first heated gently, then intensely to drive off all the water. The final data was reported as percent hydrate with 95% confidence level.

RESULTS & DISCUSSION

Weights of the crucible. The weights of the crucible are shown in the table 1:

Table 1. Weights of the Crucible