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Chemical Reactions

Investigation 2 – Lab

 

 

 

 

 

 

 

MINDSET

This Investigation is designed to:

  • demonstrate the Law of Conservation of Matter to you,
  • allow you to investigate the relationship between the amounts of two reactants,
  • allow you to investigate how the amount of each of two reactants affects the amount of a product, and
  • allow you to investigate what occurs in a chemical reaction when one of two reactants is present in a limiting amount.

BE PREPARED

Student Preparation for the Investigation includes having students gather the following materials. This preparation takes place on lab day after student lab groups have settled at their assigned lab tables.

Note: The materials are listed in students’ SDRs. They are also listed below for your reference.

  • (1) triple beam balance
  • (1) 500 ml Erlenmeyer flask
  • (1) lab scoop
  • (1) weigh dish
  • (6) large balloons
  • (1) 15 ml centrifuge tube
  • (1) 100 ml graduated cylinder
  • 3.5 g of magnesium metal in a 50 ml beaker
  • (1) 400 ml beaker
  • 350 ml of hydrochloric acid in a 400 ml beaker
  • (1) metric ruler
  • (1) calculator
  • (1) stopwatch
  • (1) pair goggles per student
  • (1) pair gloves per student

Direct one student from each lab group to collect the materials listed in their SDRs.

INVESTIGATE

  •  You will perform six Trials during this Investigation. The first five Trials use the same mass of magnesium metal but different volumes of HCl. The last Trial uses a different mass of magnesium metal.
  • Use Table A as a guide for the volume of hydrochloric acid and the mass of magnesium needed for each Trial.

CHEM2 Table A

  • Reflect on the PreLab video as you move through the procedural steps.
  • During the Experiment, every procedural step is important. If one step is skipped, data can become invalid. To help you keep on track, read each step thoroughly, complete the step, then check it off (Read it – Do it – Check it).
  • Remember to wear gloves, safety eyewear, and lab coats when handling chemicals.
  • Complete all of the procedural steps in your SDR.

Note: The procedural steps are listed below for your reference.

Note: If you need assistance, refer to the Procedural Toolbox for Triple Beam Balance Equilibration, Triple Beam Balance Use and Operation, and Measuring Mass Using a Weigh Dish or Beaker.

Note: In each Trial, you will collect the hydrogen gas (H2) in a balloon. The magnesium metal needed for each Trial is placed in the balloon which is then secured over the mouth of the Erlenmeyer flask containing the HCl. Once the balloon is secured, the magnesium is emptied into the HCl and the reaction is initiated. The reaction is complete when no more bubbles of gas are produced, approximately 5 minutes for each Trial.

Note: The volume of H2 gas produced is estimated by determining the diameter of the inflated balloon after the completion of the reaction.

 Trial 1

  1. In this Trial, you will investigate the reaction of 2 ml of hydrochloric acid (HCl) with 0.5 g of magnesium.
    1. Use the centrifuge tube to measure 2 ml of HCl and add it to the Erlenmeyer flask.
    2. Use the triple beam balance, lab scoop, and weigh dish to measure 0.5 g of magnesium.
    3. Blow up each balloon to stretch and then deflate it. Use the lab scoop to add the 0.5 g of magnesium to a balloon.
    4. Stretch the open end of the balloon over the mouth of the Erlenmeyer flask until it securely covers the mouth of the flask. During this step, do not allow any magnesium metal to fall into the flask.
    5. Use the triple beam balance to determine the total mass of the flask, hydrochloric acid (HCl), balloon, and magnesium.
  2. Record: Write the mass for “Before Reaction” in Table B.
  3. Making sure that the balloon does not come off the mouth of the flask, hold the balloon and shake the magnesium out of the balloon until all of it has fallen to the bottom of the flask into the hydrochloric acid (HCl).
  4. Gently swirl the flask, so the magnesium stays in contact with the hydrochloric acid. After approximately 5 minutes, the production of the product, hydrogen gas (H2), will have stopped. Do not remove the balloon.
  5. Using the triple beam balance, determine the total mass of the flask, hydrochloric acid (HCl), balloon, and any remaining magnesium metal.
  6. Record: Write the mass for “After Reaction” in Table B.

 

Trial 2

  1. In this Trial, you will investigate the reaction of 15 ml of hydrochloric acid (HCl) with 0.5 g of magnesium.
  2. Using the 100 ml graduated cylinder, measure 15 ml of hydrochloric acid (HCl) and add it to the Erlenmeyer flask.
  3. Use the triple beam balance, lab scoop, and weigh dish to measure 0.5 g of magnesium. Add the 0.5 g of magnesium to a new balloon.
  4. Stretch the open end of the balloon over the mouth of the Erlenmeyer flask until it securely covers the mouth of the flask. During this step, do not allow any magnesium to fall into the flask.
  5. Making sure that the balloon does not come off the mouth of the flask, hold the balloon and shake the magnesium out of the balloon until all of it has fallen to the bottom of the flask into the hydrochloric acid.
  6. Gently swirl the flask so the magnesium stays in contact with the hydrochloric acid. After approximately 5 minutes, the production of the hydrogen gas will have stopped. Do not remove the balloon.
  7. To find out how much hydrogen was produced, use the metric ruler to measure the diameter of the balloon in centimeters.
  8. Record: Enter the diameter of the balloon in Table C in the row for Trial 2.

Trial 3

  1. Repeat the procedure used for Trial 2 using 50 ml of hydrochloric acid and 0.5 g of magnesium.
  2. Record: Enter the diameter of the balloon for Trail 3 in Table C.

Trial 4

  1. Repeat the procedure used for Trial 2 using 75 ml of hydrochloric acid and 0.5 g of magnesium.
  2. Record: Enter the diameter of the balloon for Trial 4 in Table C.

Trial 5

  1. Repeat the procedure used for Trial 2 using 100 ml of hydrochloric acid and 0.5 g of magnesium.
  2. Record: Enter the diameter of the balloon for Trial 5 in Table C.

Trial 6

  1. Repeat the procedure used for Trial 2 using 100 ml of hydrochloric acid and 1 g of magnesium.
  2. Record: Enter the diameter of the balloon for Trial 6 in Table C.

 

CLEAN UP

Be sure to clean up your lab bench after completing the Investigation.