The identity of an unknown hydrate was determined by massing the hydrate before and after heating and calculating the percentage of water.
First, we cleaned, dried and heated an evaporating dish for five minutes on an iron ring with the Bunsen burner and massed it. Then, we added 2 grams of an unknown hydrate and calculated the mass of that. Next, we used gradually increasing heat for six minutes to dehydrate the solution, and we allowed it to cool for five minutes. We then massed it after cooling. We also wrote detailed observations. After this, we used our data to calculate the percent water of the solution using the appropriate equation which can be seen in the calculations section. Finally, we did a second trial to check the consistency of our data and cleaned up the lab station.
Unknown ID A
| Trial 1| Trial 2|
1. Mass of Evaporating Dish (g)| 46.339 g| 46.348 g|
2. Mass of Evaporating dish + unknown (g)| 48.420 g| 48.350 g| 3. Mass of Unknown (Data 2 – Data 1)| 2.081 g| 2.002 g| 4. Mass of Unknown +dish after heating (g)| 47.379 g| 47.320 g| 5. Mass of water lost(Data 2 – Data 4)| 1.041g| 1.030 g| 6. Percent Water in unknown(Data 5 / Data 3) X 100| 50.024 %| 51.449 %| 7. Percent Error| 2.297 %| .486 %|
Observations – Trial 1: The hydrate is bubbling and some of it is melting and becoming a liquid. Evaporation is occurring and the melted part is hardening to form a consistent solid. The sample is sticking together instead of being in separate granules. The sample has dried up and is becoming crusty. Trial 2: The observations of trial 1 are the same as what occurred in trial 2.
See other page.
After completing the lab we identified our unknown hydrate (ID A) as MgSO4∙7H2O. We did this by calculating the percent water of our unknown hydrate and comparing it to...