1. SURVEY OF CHEMISTRY LABORATORY I EMPIRICAL FORMULA OF ZINC CHLORIDE
CHEM 1151L
EMPIRICAL FORMULA OF ZINC CHLORIDE

2. CAUTION!!!
BE SURE TO WEAR SAFETY GLASSES AT ALL TIMES IN THE LABORATORY NO EXCEPTIONS TO THIS RULE!

3. EMPIRICAL FORMULA OF ZINC CHLORIDE
Students will determine - the empirical formula of zinc chloride by a process known as synthesis - the empirical formula from their data - the empirical formula from the class average It is best to perform several experiments and obtain average values for the result

4. EMPIRICAL FORMULA
- The lowest whole number ratio of atoms present in a compound - the lowest whole number ratio of moles of atoms in a compound For example - The molecular formula of glucose is C6H12O6 - The empirical formula is CH2O

5. EMPIRICAL FORMULA
Can be determined by the following methods Analysis - A compound is broken down into its element - The mount of each element present is accurately determined Synthesis - Prepared from accurately measured amounts of each of its elements

6. EMPIRICAL FORMULA
- Determine the mass of each element found in the formula (may be grams or percentage composition by mass) - Convert each mass to moles using the atomic masses of the appropriate elements - Divide each mole amount by the smallest number of moles - Round each mole ratio to the nearest integer - Write the whole numbers as subscripts in the formula

7. EMPIRICAL FORMULA
Determine the empirical formula of a compound whose composition is
determined to be 74.83% carbon and 25.17% hydrogen
Assume g sample
% of each element equals grams
C H
1.000 ≈ ≈ 4
Empirical Formula: CH4

8. - Mass about 1 gram of zinc metal - Record this mass

9. - Mass a clean, dry evaporating dish - Record this mass

10. HYCHLORIC ACID
- Use the automatic dispensing bottle - Dispense 10 mL of 12 M hydrochloric acid (HCl) directly into the evaporating dish

11. HYCHLORIC ACID + ZINC METAL
- Carefully add the zinc to the dish containing the HCl - Must be done in the hood - Allow all of the zinc to dissolve

12. EVAPORATE LIQUID
- Gently warm solution on a hotplate - Must be done in the hood - Avoid spattering - A white powdery substance (zinc chloride) will form

13. COOL AND MASS PRODUCT
- Avoid melting of zinc chloride - Take the dish off the hotplate when content is dried enough - Allow the dish to cool

14. - Mass the dish and the zinc chloride - Record the mass
COOL AND MASS PRODUCT
- Mass the dish and the zinc chloride - Record the mass

15. CALCULATIONS
- Complete your calculations on the data sheet - Report the percent by mass of each element to the instructor before leaving the lab - The class average is needed to complete the lab report