Determine the Chemical Formula for Zinc Chloride
Apparatus: Balance
Graduated cylinder
Evaporating dish
Stirring rod
Bunsen burner
Wire gauze
Ring stand and ring
Chemicals: Granular zinc (0.4 - 0.5 grams)
6 M HCl (density = 1.098gm/ml)
Elemental zinc reacts with hydrochloric acid in the following manner:
Zn (s) + 2 HCl  ZnCl2 (aq) + H2 (g)
This type of reaction is referred to as a single displacement reaction. Zinc displaces hydrogen. The reaction is
also an oxidation/reduction reaction. In this reaction zinc loses 2 electrons (oxidation) to achieve an
oxidation state of +2. Hydrogen gains an electron (reduction) to go from a +1 oxidation state to zero as
elemental hydrogen. Your task is to experimentally determine the empirical formula for zinc chloride.
Procedure: 1- Determine what measurements are required
2- After massing your zinc, determine how much HCl is required
3- Carry out the reaction in the fume hood. Add HCl if zinc remains unreacted.
4- Carefully heat the evaporating dish to remove excess HCl.
5- When your zinc chloride becomes white and pasty, stop heating. Place a piece of foil over the
dish while it is cooling. ZnCl2 is very deliquescent. When the dish has cooled to about room
temperature, remove the foil and mass.
6- After massing, carefully reheat the sample for roughly a minute. ZnCl2 sublimes very easily so
the reheat should be short and gentle. Mass the sample. If the 2 readings are plus/minus .02
grams, you are finished. If not, reheat again.
EYE PROTECTION MUST BE WORN AT ALL TIMES !!
IF IT IS NOT, YOU WILL RECEIVE A 5 POINT PENALTY ON YOUR GRADE
Questions: 1- How would the empirical formula be affected if your solution spattered?
2- How would the empirical formula be affected if you failed to heat to a constant mass?
3- How would the empirical formula be affected if the compound sublimed?
4- How would the empirical formula be affected if the zinc contained an inert impurity?
Lab Book Write-up:1- Title
2- Data table
3- All pertinent calculations including % error
4- Good analytic answers to the questions
Do not forget to complete the table of contents and number your pages.