Chemical Reactions Lab



Chemical Reactions Lab

You will examine the different types of reactions and how to write balanced chemical equations in this lab.

Pre-Lab Requirements:

For each of the experimental parts below, create some structured method to take both quantitative and qualitative observations. Refresh your memory on heating substances in crucibles and test tubes from the safety information from the beginning of the semester.

NOTE: Taking good qualitative and quantitative observations during the lab and demonstrations will be the key to your being able to write the react ions for this lab.

In the Lab:

Part A: Magnesium

1. Check your crucible carefully for cracks and make sure it is completely dry.

2. Obtain a piece of magnesium about 3.00 cm in length and coil it so it fits in the bottom of your crucible. Mass your crucible, lid, and magnesium together.

3. Heat the crucible using the hottest part of the Bunsen burner flame with the lid securely on the crucible until the crucible glows red hot on the bottom. Remove the lid briefly with crucible tongs and then return it. In your observations, note what occurs when you open the lid. Repeat this process roughly every minute until you see no light other than the glowing crucible upon removing the lid. Then heat the crucible for two to three minutes with the lid off.

4. Remove the flame and allow the crucible to cool on the wire gauze. When it is completely cool, remass the crucible, lid, and your product.

5. Scrape the product into the trash can. Bring the crucible to Mrs. Atkins to clean.

Part B: Copper(II) carbonate

1. Obtain roughly 1.0g of copper(II) carbonate and place it in the dry test tube. Mass the copper(II) carbonate in the test tube.

2. Clamp the test tube to a ring stand so it is at a 45° angle to the lab bench. Gently heat the copper(II) carbonate by using a distant low flame that has no inner blue cone. Observe any changes that occur during heating. After about 2 minutes, light a wooden splint and insert the flaming splint into the mouth of the test tube. Note what happens to the flaming splint..

3. Continue to heat until no more evidence of chemical reaction is observed. Allow everything to cool. Re-mass the copper(II) carbonate. Place the solid waste in the trash can.

4. Because this step is dangerous, Mrs. Atkins will also do this reaction as a demonstration and capture the gas being produced from this reaction by bubbling the gas generated by the reaction through a tube of limewater. The limewater test checks for the presence of carbon dioxide. Limewater is a saturated solution of calcium hydroxide. When carbon dioxide is bubbled through limewater the following reaction occurs:

Ca(OH)2(aq) + CO2(g) ( CaCO3(s) + H2O(ℓ).

The calcium carbonate precipitate makes the limewater look cloudy.

Part C: Zinc and Hydrochloric Acid

1. Obtain two large test tubes, a test tube rack, and a test tube holder. Mass one small piece of zinc and place it in one of the test tubes. Place the test tube containing the zinc in the test tube rack.

2. Obtain roughly 5.0 mL of 6M HCl(aq), add it to the zinc and quickly collect the gas that evolves in an upside down empty test tube using test tube holders.

Caution: Hydrochloric acid, HCl(aq), is very corrosive and damaging. Use care and report and clean up any spills promptly.

3. After about 45 seconds move the test tube containing the gas at least 2 feet away from the test tube containing the zinc and HCl while keeping the test tube inverted. Hold a lit match horizontally and place it under the mouth of the test tube. Repeat this process until no sound is heard.

4. Unclamp the tube with the zinc and HCl and fill it completely full with water and gently pour the liquid down the drain. DO NOT let any solid go into the sink. Remove the unreacted zinc from the test tube, dry it thoroughly and remass it. Place the used zinc in the trashcan.

5. The “flaming splint” test is used to test for the presence of hydrogen gas. Hydrogen gas is very flammable and reacts quickly with the available oxygen in the air by the following reaction:

H2(g) + O2(g) ( H2O(ℓ)

Part D: Blended Smurf

1. Place 1 full squirt of 1M copper(II) chloride in a clean test tube. Add another 2 full squirts of 1M sodium hydroxide to the test tube. Make observations immediately and after the test tube has been allowed to sit undisturbed for five minutes.

2. Pour the liquid waste into the beaker labeled Part D Waste. Use the wash bottle nearby to attempt to rinse out as much solid waste into the beaker as well. Then clean your test tube thoroughly with your test tube brush and a small amount of soap.

Part E: Copper and Zinc

1. Get one piece of fresh zinc, place it in a test tube, and add 1 full squirt of 1M copper(II) chloride solution. Allow the test tube to sit for 5 minutes, record your observations and pour the waste in the beaker labeled Part E Waste.

Part F: “Elephant Toothpaste”

1. Record observations about this teacher demonstration.

Part G: Methanol

1. Record observations about this teacher demonstration.

Lab Report:

A) Purpose

B) Analysis Questions

1) For each of the parts (A-G) of this experiment write:

a. A balanced reaction for each of the main reactions, including all appropriate symbols (Include all main reactions for Parts A-G – reactions are not necessary for the additional tests performed).

b. All of the specific evidence from your observations that supports your overall reaction as written and/or and specific products you observed, including an explanation of how this evidence supports your reaction or the specific product. You should have a brief explanation for each reaction, including your evidence from the lab, that tells me how you knew which products were generated by the reaction. Look at each of the steps you did for the reaction and at the information I asked you to record for your supporting evidence.

c. A classification of the reaction as one of the five types we have discussed.

2) Research the mechanism of the catalyst in the Elephant Toothpaste demonstration. A mechanism is a step- by-step description of exactly how the reaction happens involving multiple reaction steps. Write the balanced reactions involved and explain why we consider the compound a catalyst and not a reactant. Please cite all sources properly in MLA format, using in-text citations where appropriate.

C) Conclusions

D) Original Data Sheet

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