1. To determine the % of water in a unknown hydrate.
2. To determine the moles of water present in each mole of this unknown hydrate, when give the molar mass of the anhydrous salt.
3. To write the empirical formular of the hydrate.
Supplies:
lab burnet, ring stand and ring, crucible and lid, centigram or digital balance, crucible tongs, pipestem triangle, lab apron, safety goggles.
Chemical Reagents: approximately 5g of hydrate, water.
ProcedureMass a crucible and its cover and record in a data table. Place about 2 grams of the hydrate in the crucible and record the mass of the crucible, cover and hydrated salt. Gently heat the crucible and its contents for about 10 minutes. During the last minute of heating remove the cover so that any moisture which has collected on the underside of the cover can evaporate. When the crucible has cooled determine the mass of the crucible, cover, and contents.
Replace the cover and heat the crucible for five more minutes removing the cover during the last minute of heating as you did above. Cool and determine the mass of the crucible, cover, and contents. This last mass should agree with the previous mass to within plus or minus 0.005 grams. If it does not repeat this heating until a constant mass is reached. This is called heating to a constant mass and is the only way of insuring that the reaction is complete.
Data:
Mass of empty crucible and lid 13.12g
Mass of crucible, lid and hydrate 15.34g
Mass of hydrate 2.22g
Mass of crucible, lid and anhydrous salt(first) 14.54g
Mass of crucible, lid and anhydrous salt(second) 14.55g
Mass of anhydrous salt 1.42g
Mass of water given off 0.82g
Mass of one mole of hydrous salt(from your instructor) 159.6g/mol
Describle any changes that you observed when adding water to the crucible Become blue solid.
没有评论:
发表评论