lab report
Name: _____________________________
9
Exp. 4. Report Form: Determination of the (Empirical) Formula of a Hydrate
A. Questions and Observations Associated with the Procedure
1. What is the color of the crystals of CuxCly zH2O that are added to the crucible? __________________
2. Why is the heating done gently, rather than intensely (as last week)?
3. Describe what you saw during the heating as far as color goes. Does the solid all change at the same time and in the
same physical place in the sample or does it start in one area and then progress to other area(s)?
4. (i) Describe the two major changes, visually, that occurred in the beaker over the course of the first 5-10 minutes after
the wire is dropped into the solution. One of these is associated with the solution, the other with the wire.
NOTE: I do not mean the formation of bubbles here—those are not actually associated with the reaction of interest (ask, if you are interested
about the bubbles.).
(ii) What are you to assume is occurring at the molecular level to explain each of these changes?
(iii) Describe the other change (not “visual”) that occurred during the reaction, which you should have felt with your
hand during the procedure. What do you think this indicates about the reaction(s) that are occurring in the beaker
during this time?
5. After the copper is transferred to the filter paper in the Buchner funnel and washed well with water, one liquid
(ethanol, 95%) is added, allowed to sit for a bit, and then pushed through under low pressure via vacuum filtration.
Then another liquid (acetone) is used similarly, and air is drawn through via vacuum for 8 or so minutes. What is the
purpose of these steps?
Report Form, Determination of the (Empirical) Formula of a Hydrate
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B. Raw Data That Are Measurements (not observations)
Mass of crucible (without cover) __________________
Mass of (uncovered) crucible with solid hydrate __________________
Mass of (uncovered) crucible and residue, Reading 1
(after cooling for a total of _____ min; still warm? Y or N?) __________________
Mass of (uncovered) crucible and residue, Reading 2
(after cooling for a total of _____ min; still warm? Y or N?) __________________
Mass of (uncovered) crucible and residue, Reading 3 (ONLY IF NEEDED)
(after cooling for a total of _____ min; still warm? Y or N?) __________________
Mass of filter paper __________________
Mass of watch glass __________________
(final) Mass of watch glass + filter paper + copper (once fully dry) __________________
Calculated Quantities and Results (SHOW ALL SETUPS):
Mass of solid hydrate sample __________________
Mass of residue (anhydrous compound) __________________
Mass of H2O in hydrate sample (assume all mass lost on heating is due to water loss) __________________
Mass of copper in hydrate sample __________________
Mass of chlorine in hydrate sample (assume any mass in the sample unaccounted for is due to Cl) __________________
Moles of H2O in hydrate sample __________________
Moles of copper in hydrate sample __________________
Moles of chlorine in hydrate sample __________________
Mole ratio, Cl (atoms) to Cu (atoms) in hydrate sample _________: 1 ____: 1
Mole ratio, H2O (molecules) to Cu (atoms) in hydrate sample _________: 1 ____: 1
Formula of the anhydrous compound (dehydrated compound) __________________
Formula of the hydrate (hydrated compound) __________________
(to proper # of SF) (nearest integer)
(to proper # of SF) (nearest integer)
Report Form, Determination of the (Empirical) Formula of a Hydrate
11
C. (Optional) Raw Data from Data Set Data Set #:______ Formula of Hydrate (with x, y, z): _________________
Mass of crucible __________________
Mass of crucible and solid hydrate __________________
Mass of crucible and residue (fully cooled) __________________
Mass of filter paper __________________
Mass of watch glass __________________
Mass of watch glass + filter paper + metal (fully dry) __________________
Calculated Quantities and Results (SHOW ALL SETUPS):
Mass of solid hydrate sample __________________
Mass of residue (anhydrous compound) __________________
Mass of H2O in hydrate sample (assume all mass lost on heating is due to water loss) __________________
Mass of _____________ [your metal] in hydrate sample __________________
Mass of _____________ [your anion element Cl or Br] in hydrate sample __________________ (by difference, as above.)
Moles of H2O in hydrate sample __________________
Moles of ______________[your metal] in hydrate sample __________________
Moles of ______________[your anion element] in hydrate sample __________________
Mole ratio, _____ [Cl or Br] (atoms) to _____ [your metal] (atoms) in hydrate sample _________: 1 ____: 1
Mole ratio, H2O (molecules) to _____[your metal] (atoms) in hydrate sample _________: 1 ____: 1
Formula of the anhydrous compound (dehydrated compound) __________________
Formula of the hydrate (hydrated compound) __________________
(to proper # of SF) (nearest integer)
(to proper # of SF) (nearest integer)