Analysis of Hydrates
Pre -Lab Questions
- Define each of the following terms:
- Hydrate- A compound, typically a crystalline one, in which water molecules are chemically bound to another compound or an element.
- Efflorescent compound- A chemical which has water associated with its molecules, and which, when exposed to air, loses this water through evaporation.
- Deliquescent compound- The process by which a substance absorbs moisture from the atmosphere until it dissolves in the absorbed water and forms a solution.
- Hygroscopic compound- one that readily attracts water from its surroundings, through either absorption or adsorption.
- Anhydrous compound- Substances without water are anhydrous. The term is most often applied to crystalline substances when the water of crystallization is removed.
- Write a balanced equation for the dehydration of CoCl2*6 H2O
CoCl2 + 6H2O
- Write a balanced equation for the reaction between water and the residue produced by heat CoCl2 * 6 H2O
CoCl2 + 6H2O- Driving off the water of hydration isn't really a chemical reaction -- it's a physical change.
- Why must tongs be used to handle the crucible
Because the crucible is extremely hot even if it doesn’t seem like it is
Analysis of Hydrates
Report
- Spontaneous Change
Initial observation Clay containers, 2 pc, blue substance
My initial observation there is a very juvenile dark blue substance and over time and after placing heat within the first hour the substance began to loose its dark blue color
Final observation Crystalized, white, dry
My final observation was that the once dark blue substance was now a dried up white crystalized substance
- Spontaneous Change
Mass of crucible/cover 30.316g
Mass of crucible, cover, hydrate 33.010g
Mass of crucible, cover, residue (first heating) 32.658 g
Mass of crucible, cover, residue (second heating) 32.223 g
Mass of crucible, cover, residue (third heating) 32.116 g
ID # OF Unk Hydrate EFH5
Unk Hydrate formula CuSO4
- Dehydration
Original color of crystals Dark blue
Color of crystals after heating White
Color of crystal after adding heat lighter blue
Post-Lab Questions
- From the observation, determine whether NaOH is efflorescent or deliquescent compound. Explain how you decided. Why would it be difficult to weigh a sample of NaOH? How might this be overcome?
NaOH is deliquescent. This is the type of material is so sensitive that If you take NaOH out of its reagent bottle and leave it in the open it will drawl in water from the atmosphere and it will turn into a puddle by picking up water. NaOH crystals can’t be weighed normally because in a normal room it will absorb water thus changing its original weight. In order to overcome this, you would need an extremely dry and special area.