Prepare the following test solutions Approximately 0.5 M KOH by diluting 20 mL of 6 M KOH into the appropriate volume of distilled water. You may use a 100-mL graduated cylinder repeatedly to reach your final volume. Show your calculations here: What should be the final volume? ______ (Store this solution in the provided bottle; label the bottle with your name and “0.5M KOH”) Approximately 0.5 M HCl by diluting 5 mL of 6 M HCl into the appropriate volume of distilled water. You may use a 100-mL graduated cylinder to measure your final volume. It doesn’t need to be exact. Show your calculations here: What should be the final volume? ______ Put enough solid NaCl to cover the bottom curve of a large test tube. Dissolve in about 15 mL of distilled water. Litmus paper test: Place about 2 mL of each one of the three test solutions made in step 1 into separate small test tubes. Use a glass stirring rod to just touch the surface of one of the solutions. Touch the wet tip of the stirring rod to one end of a blue litmus paper strip and then to the end of a red litmus paper strip. Rinse the stirring rod (use your wash bottle with distilled water) and repeat for each solution. Don’t waste pH paper; you can use one strip for all three tests! WATCH THE VIDEO AND WRITE YOUR OBSERVATIONS: Solution Blue Litmus Red Litmus NaCl KOH HCl Flame test You will use the same samples from Step 2. Turn on your Bunsen burner to obtain a flame with an inner blue cone. Put about 20 mL of distilled water in a small beaker. Obtain three wet wood splints from instructor and place them in the beaker with distilled water. Take one of the wood splints and place it in the flame. There should be no significant change in the color of the flame. Now dip the wood splint in the NaCl sample from Step 2. Place it in the flame and observe. You should see a bright yellow color flame that indicates the presence of sodium ions. Repeat the the flame test with another wood splint and the HCl sample from Step 2. Repeat the the flame test with another wood splint and the KOH sample from Step 2. NOTE: Don’t leave the wood splint in the flame for more than a few seconds at a time. WATCH THE VIDEO AND WRITE YOUR OBSERVATIONS: Solution Flame color NaCl KOH HCl
PROCEDURES (PART A)
- Prepare the following test solutions
- Approximately 0.5 M KOH by diluting 20 mL of 6 M KOH into the appropriate volume of distilled water. You may use a 100-mL graduated cylinder repeatedly to reach your final volume. Show your calculations here:
What should be the final volume? ______
(Store this solution in the provided bottle; label the bottle with your name and “0.5M KOH”)
- Approximately 0.5 M HCl by diluting 5 mL of 6 M HCl into the appropriate volume of distilled water. You may use a 100-mL graduated cylinder to measure your final volume. It doesn’t need to be exact. Show your calculations here:
What should be the final volume? ______
- Put enough solid NaCl to cover the bottom curve of a large test tube. Dissolve in about 15 mL of distilled water.
- Litmus paper test:
- Place about 2 mL of each one of the three test solutions made in step 1 into separate small test tubes.
- Use a glass stirring rod to just touch the surface of one of the solutions. Touch the wet tip of the stirring rod to one end of a blue litmus paper strip and then to the end of a red litmus paper strip.
- Rinse the stirring rod (use your wash bottle with distilled water) and repeat for each solution. Don’t waste pH paper; you can use one strip for all three tests!
WATCH THE VIDEO AND WRITE YOUR OBSERVATIONS:
Solution |
Blue Litmus |
Red Litmus |
NaCl |
|
|
KOH |
|
|
HCl |
|
|
- Flame test
- You will use the same samples from Step 2.
- Turn on your Bunsen burner to obtain a flame with an inner blue cone.
- Put about 20 mL of distilled water in a small beaker.
- Obtain three wet wood splints from instructor and place them in the beaker with distilled water. Take one of the wood splints and place it in the flame. There should be no significant change in the color of the flame.
- Now dip the wood splint in the NaCl sample from Step 2. Place it in the flame and observe. You should see a bright yellow color flame that indicates the presence of sodium ions.
- Repeat the the flame test with another wood splint and the HCl sample from Step 2.
- Repeat the the flame test with another wood splint and the KOH sample from Step 2.
NOTE: Don’t leave the wood splint in the flame for more than a few seconds at a time.
WATCH THE VIDEO AND WRITE YOUR OBSERVATIONS:
Solution |
Flame color |
NaCl |
|
KOH |
|
HCl |
|
- Indicator test
- You will use the same samples from Step 2.
- To each sample, add one drop of phenolphthalein indicator solution
WATCH THE VIDEO AND WRITE YOUR OBSERVATIONS:
Solution |
Color after addition of indicator |
NaCl |
|
KOH |
|
HCl |
|
[NOTE: “Clear” is NOT a color description. “Colorless” is appropriate to describe absence of color.]
- Neutralization reaction
- You will use the solutions you prepared in Step 1.
- WRITE the balanced equation for the neutralization reaction between HCl and KOH
EQUATION:
- Place about 1 mL of the HCl test solution into a clean test tube. This is about 20 drops.
- Add KOH test solution drop wise, using a litmus paper strip to test the acidity of your mixture. Based on the stoichiometry of the equation and the approximate concentrations of the two solutions, you can more or less guess how much KOH solution you will need to neutralize the HCl.
Generally 20 drops is about 1 mL.
1. This is where you are going to put some thought: What color of litmus paper should you use to track the progress of the reaction?
2. Write your observations:
Litmus paper chosen: _____red _____blue
Color of litmus paper with HCl before addition of KOH: _____________
Color of litmus paper with HCl after neutralization with KOH: _____________
(Estimate) Number of drops of KOH (aq) required to neutralize the HCl: _______
3. Transfer the reaction mixture to an evaporating dish and place the dish so that it rests on the rim of a beaker with boiling water.
4. Inspect the evaporating dish to detect the presence of any remaining solid. Re-dissolve the solid in about 1 mL of distilled water and perform a flame test on the new solution. Based on your results from Step 3 predict what you expect to observe:
Predict: is there a solid on evaporating dish after vaporizing liquid? ___ Yes ___ No
Predicted result of flame test: _____________________________
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