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

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

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

    3. 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. - 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. 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. - 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.

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

    9. EVAPORATING DISH - 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. 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

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