EXPERIMENT 4: HYDRATED SALT FORMULA

Objectives:

1. To determined the volume of water content in hydrated salt.

2. To determined the formula of hydrated salt.

Materials/apparatus:

Crucible or test tube with cover

Retort stand

Bunsen burner

Thermometer

Balance

Hydrated salt : CuSO4.XH2O

Methods:

1. The crucible is heated for a while

2. The crucible are weight with its cover

3. Approxiamately add 2 gram of hydrated salt, weight and record the data

4. Salt are heat gradually in crucible without its cover for around 3-5 minutes

5. Any colour changes are observed.

6. Stop heating, cover the crucible and wait until cool.

7. Observed

8. Weight

9. The salt need to grind using the glass rode and heat again.

10. The salt need to cool in the room temperature

11. Weight again.Continue heating until the weight constant.

*Cool the sample in the decicator if needed.

12. The salt temperature are record after thefinal weight.

13. Add a few drop of water at room temperature, record the temperature.

14. Observed.

Result:

Mass of crucible : 40.0490g

Mass of head crucible : 2.64730g

Mass of crucible + head : 42.6990g

Mass of crucible + CuSO4.XH2O after 1st heating : 41.3267g

Mass of crucible + CuSO4.XH2O after 2nd heating : 41.3066g

Mass of crucible + CuSO4.XH2O after 3rd heating : 41.2858g

Mass of crucible + CuSO4.XH2O after 4th heating : 41.2858g

Initial temperature (°C) of CuSO4.XH2O : 31C

Final temperature (°C) of CuSO4.XH2O after add water : 35C

Mass of CuSO4.XH2O : 1.2368g

Mass of H2O : 0.7632g

Element present CuSO4 H2O

Mass(g) 1.2368g 0.7682g

Number of moles 1.2368 =0.00773

160

0.7682 =0.0424

18

Simplest mole ratio 0.00773

0.00773

= 1

0.0424

0.00773

= 5.4

1 5.4

Colour of CuSO4.XH2O heat (without cover) : white green

Colour of CuSO4.XH2O after heat (with cover) : white yellow

Disscussion:

Before we start the experiment, the crucible need to be heat for a several second

in order to dry out all the water that could be wet the crucible. During the heating

prosecess the salt in crucible need to been burn in open crucible without close it. It is due

to make the oxygen gas can react with the salt to help the burning process. After heat the

salt, we need to cool it in the room temperature and the head of crucible closed with it

head. It is because to prevent the air from the outside enter and react with the dry salt. In

this experiment, we need to heat and cold the salt for a several times in order to get the

constant weight of salt. After getting the constant weight of the salt, we need to record it

final temperature. After that, we add some water and record its final temperature. From

experiment we see that the temperature of the salt are increased to 35.That mean the salt

undergoes the exothermic process. During the experiment, there are several error could

occur .For example, during the weighing process, heating and cooling processes. The

actual value according to its molecular formula is 5 and it is correctly approximate with

our result that is 5.4.

Conclusion

As the conclusion, by doing the empirical method we can determined the number of

moles in the given substance of the element. Moreover this method also help us to find

the real molecular formula.