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CP Lab 1a Conservation of mass

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					CP Lab 1a: Conservation of mass

Purpose: to investigate if mass remains the constant in a number of chemical reactions.

Apparatus: Pipettes, electronic balance, plastic bottle

Chemicals: Alka-Seltzer, calcium chloride, sodium carbonate, water, sodium hydroxide, hydrochloric
acid, phenolphthalein

Procedure:                             figure A



PART A: Precipitation

    1. Add a few drops of calcium chloride solution into a pipette.
    2. Into a second pipette add a few drops of sodium carbonate solution and snip the end with a
       scissor.
    3. Connect the two pipettes together. (figure a )
    4. Place apparatus on balance and record the mass of the whole unit.
    5. Mix the solutions together by gently squeezing the longer pipette into the shorter pipette.
    6. IT IS IMPORTANT TO NOT SPILL CONTENTS!!!
    7. Record observations in data table and place on balance again and record the mass.
    8. Repeat steps 1-6 twice more.

PART B: Formation of a Gas

    1.   Take a plastic bottle and add 10mL of water.
    2.   Place ¼ of an alka - seltzer tablet inside the cap.
    3.   Place the bottle and the cap on the balance and record the total mass.
    4.   Drop the table into the bottle and quickly and tightly on the cap.
    5.   Shake the bottle for two minutes. Record observations.
    6.   Place the bottle on the balance and reweigh it.
    7.   Open the cap and release the gas.
    8.   Place the bottle and cap on the balance and weigh it a third time.
    9.   Repeat steps 1-8 twice more.


PART C: Color Change

    1. Add a few drops of sodium hydroxide solution into a pipette.
    2. Into a second pipette add a few drops of hydrochloric acid solution and snip the end with a
       scissor.
    3. Connect the two pipettes together. (figure a )
    4. Place apparatus on balance and record the mass of the whole unit.
    5. Mix the solutions together by gently squeezing the longer pipette into the shorter pipette.
    6. IT IS IMPORTANT TO NOT SPILL CONTENTS!!!
    7. Record observations in data table and place on balance again and record the mass. Repeat.
Data Table:

PART A: Precipitate
                      Part A                Part A
                                st
Mass BEFORE mixing             1 trial     2nd Trial   3rd trial

Observations




Mass AFTER Mixing              1st Trial   2nd Trial   3rd Trial




PART B: Gas Formation
                     Part B                 Part B
Mass BEFORE mixing             1st trial   2nd Trial   3rd trial

Observations




Mass AFTER Mixing              1st Trial   2nd Trial   3rd Trial




PART C Color Change
                      Part C                Part C
Mass BEFORE mixing             1st trial   2nd Trial   3rd trial

Observations




Mass AFTER Mixing              1st Trial   2nd Trial   3rd Trial


Conclusion Questions:
   1. For each experiment (Part A, B, & C) list the observations that suggest a chemical reaction has
      taken place.
                     Part A:


                       Part B:


                       Part C:




   2. For each experiment how does the mass of the reactants compare to the mass of the products?


                       Part A:



                       Part B:



                       Part C:



   3. For each experiment suggest possible errors that may have caused the mass to not remain
      constant.

                       Part A:




                       Part B:




                       Part C:

Theory:
Chemical reaction, reactant, product, evidence of chemical reaction, law of Conservation of Mass

				
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posted:12/4/2011
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