Lab 9: Composition of a Copper Sulfate Hydrate Lab

Lab 9

Composition of a Copper Sulfate Hydrate Lab

Shiva Senthil

7/21/17

Introduction

The purpose of this lab was to be able to find the empirical formula of a hydrate. The lab consisted of heating a hydrate and measuring the change in mass from hydrate to anhydrous salt to find the amount of water and the empirical formula of the hydrate.

Data

The hydrate before heating

The anhydrous salt left behind after heating

This table shows the mass of the dish, the dish with the hydrate, and the dish with the anhydrate after heating.

To find the mass of the hydrate, subtract the mass of the dish from the mass of the dish and hydrate:

To find the mass of the water in the hydrate, subtract the mass of the dish and anhydrate from the mass of the dish and hydrate:

To find the percentage of water in the hydrate, divide the mass of the water by the mass of the hydrate:

This formula calculates the percent error. The correct percentage of water in the copper sulfate hydrate is 36.0%:

 There is an error of about 4.7%. This may be because of slightly inaccurate measurements of mass, or heating the hydrate too much. The error is not too high, but is still significant. If there was no error, the unrounded coefficient of the water would be lower, as the actual percent of water is less than the measured percent.

The next step is to find the number of moles of each molecule, which is done by dividing the number of grams by the molar mass of the molecule.

of water

of copper sulfate

 Finally, the ratio between the water and the copper sulfate is found by dividing the number of water moles by the number of copper sulfate moles. Because of the +4.7% error, the coefficient of water is most likely too high. However, the water coefficient is rounded to the nearest whole number because it is impossible to have part of a molecule; there must be a whole particle:

 Using the 5:1 ratio of water to copper sulfate molecules, the empirical formula of copper sulfate hydrate can be written:

This is the empirical formula of copper sulfate hydrate.