Determine the Chemical Formula for Zinc Chloride



Determine the Chemical Formula for Zinc Chloride

Apparatus: Balance Bunsen burner

Graduated cylinder Wire gauze

Evaporating dish Ring stand and ring

Stirring rod

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.

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