Reactions of Acids and Bases Lab Activity

Reactions of Acids and Bases Lab Activity

Free Physical Science Worksheets

Neutralization Reactions Lab: Reactions of Acids and Bases

Reactions of Acids and Bases: We have already stated that a neutralization reaction will take place when an acid reacts with a base to form a salt and water.

The reason that it's called a neutralization reaction is because you are starting with a base (pH>7) and an acid (pH<7) and you are combining them to form a solution that has a pH closer to 7 (neutral) than each of the reactants. In other words, you're making a solution that is more neutral than its individual components.

A neutralization reaction will not always result in a pH of exactly 7.

First of all, if too much (excess) acid is used as a reactant, the extra acid will remain in the product solution, which will cause the final pH to be below 7. The opposite is true with an excess of base. In that case, the final pH of the product will be above 7.

Second, some acids and bases are stronger than others. If you mix the correct amounts and equal concentrations of a strong base and a strong acid (no excess), you'll end up with a pH of exactly 7. However, if you mix this strong base with the same amount of a weak acid, the resulting pH will be greater than 7, because the base in this case is stronger than the acid. The opposite is true for a strong acid and a weak base. If both the acid and the base are weak, the resulting pH will depend on which one is relatively stronger than the other. The chart below assumes that there is no excess acid or base fed into the reaction.

Acid/Base Reactants Product pH
Strong Acid/Strong Base 7
Strong Acid/Weak Base <7
Weak Acid/Strong Base >7
Weak Acid/Weak Base 7, <7 or >7 depending on the relative strength of the acid vs. the base

Reactions of Acids and Bases Lab Materials:

Start by downloading the Reactions of Acids and Bases Lab Worksheets.

3-11 Lab Activity Student Edition - Reactions of Acids and Bases (PDF)

3-11 Lab Activity Teacher Edition - Reactions of Acids and Bases (Member Only) (PDF)

3-11 Lab Activity SE - Reactions of Acids and Bases (Member Only) (Editable Doc)

3-11 Lab Activity TE - Reactions of Acids and Bases (Member Only) (Editable Doc)

Here is what you will need for the lab...

  • pH test strips and pH scale (at least 9 test strips)
  • Baking soda (NaHCO3(s))
  • Vinegar (CH3COOH(aq))
  • Lemon Juice (C6H8O7)
  • Hydrogen Peroxide (H2O2(aq))
  • Bleach (NaClO(aq))
  • Ammonia (NH3(aq))
  • 25-35 mL of water to make baking soda solution
  • 6 standard test tubes and test tube rack
  • Masking tape and a permanent marker
  • Paper towel or paper plate (to avoid making a mess when measuring pH)
  • 3 50-mL Erlenmeyer flasks (if you have fewer than 3 you'll just have to clean them between uses)
  • 1/2 tsp measuring spoon at least 1 10 ml graduated cylinder (you'll need 6 of these if you don't want to wash them in between uses)
  • 9 eyedroppers (if you have fewer than 9 you'll just have to clean them between uses)
  • Glass stirring rod (If you don't have one, you'll just need something small enough to stir the contents of the test tubes)
  • Safety glasses and disposable gloves

**NOTE: For your safety, only mix the chemicals as instructed. Reactions between some of the above solutions will release toxic chemicals.

Instruction:

Answer the following questions about acids, bases, pH and neutralization reactions.

You are given 7 unknown aqueous solutions labeled A-G. You need to figure out which ones will take place in a neutralization reaction, and what the resulting pH ranges will be. When you tested the pH of each solution using pH paper, your results were as follows:

Reactions of Acids and Bases

For each of the following solution pairs, determine whether the two solutions will take place in a neutralization reaction when mixed. If you decide that a neutralization reaction will occur, determine whether the resulting pH will be 7, less than 7 or greater than 7.

Reactants Neutralization Reaction?

(Y or N)

Ph (7, <7, >7, or N/A)
A & D
A & G
A & F
B & D
C & E
C & D
F & G

Which solution (A-G) is the strongest acid, and what is its pH? Which is the strongest base, and what is its pH?

Reactions of Acids and Bases Lab Procedure:

  1. With the masking tape and permanent marker, label 6 test tubes All through F. Wear safety glasses and gloves for the remainder of this procedure.
  2. Make a baking soda solution. In test tube A, mix 1/2 tsp of baking soda with 25mL of water. Stir the solution with your glass stirring rod until most of the baking soda dissolves. If a large amount of solid baking soda is still present, you can add a little more water to your solution.
  3. Fill each of the labeled test tubes about 34 full of solutions A-F:
    • Solution A: Baking soda solution (NaHCO3(s))
    • Solution B: Vinegar (CH3COOH(aq))
    • Solution C: Lemon juice (C6H8O7)
    • Solution D: Hydrogen peroxide (H2O2(aq))
    • Solution E: Bleach (NaClO(aq))
    • Solution F: Ammonia (NH3(aq))
  4. Place a pH test strip on a paper towel or a paper plate. Using an eye dropper, transfer 1-2 drops of solution Aonto the pH test strip. Record the color and the approximate ph of the solution in the table on your data sheet. Based on the pH, record whether this solution is acidic, basic or neutral. Remember to refer to your pH scale when determining the pH.
  5. Repeat step 4 for solutions "B" through F.” Remember to use a new eye dropper for each solution (or clean the used one) to avoid contamination and unwanted reactions.
  6. On the bottom half of your data sheet, you will see a table of neutralization reaction scenarios. Before moving on to step 7, fill out the "Predictions" column by making an educated guess about the pH and acidity/basicity of each product solution.
  7. Have your teacher sign off that you have predicted each reaction outcome.
  8. Reaction #1: Bleach (E) and Hydrogen peroxide (D)
    • Measure 8mL of hydrogen peroxide into a 10ml graduated cylinder. Pour the hydrogen peroxide into an empty Erlenmeyer flask. If you only have access to one graduated cylinder, wash it with water before continuing.
    • Measure 8 ml of bleach into a 10ml graduated cylinder.
    • CAREFULLY pour the bleach from the graduated cylinder into the flask containing 8mL of hydrogen peroxide. Watch the reaction go to completion. You may need to swirl the solution or stir it with your glass stirring rod to help the reaction along.
    • When the reaction is complete, use a clean dropper to transfer 1-2 drops of the new solution onto a pH test strip. Record the approximate pH of the solution in the table on your data sheet. Based on the pH, record whether this solution is acidic, basic or neutral. Remember to refer to your pH scale when determining the ph.
  9. Repeat step 8 for Reaction #2 (Baking Soda (A) and Lemon Juice (C)) and Reaction #3. (Baking Soda (A) and Vinegar (B)). Remember to measure each reactant using clean lab equipment to avoid contamination and unwanted reactions!
  10. Make sure your data sheet is complete, then complete the Results and Discussion" section of the lab.
  11. Clean all of your lab equipment. Have your teacher sign off that your lab equipment has been cleaned and properly put away.

Data Sheet

Directions: Fill out this table as you complete steps 4 and 5 of the procedure.

Solution pH Paper Color Approximate pH Acid, Base, or Neutral
A. Baking soda solution (NaHCO3(s))
B. Vinegar (CH3COOH(aq))
C. Lemon juice (C6H8O7)
D. Hydrogen peroxide (H2O2(aq))
E. Bleach (NaClO(aq))
F. Ammonia (NH3(aq))

Directions: Fill out the Prediction column for each reaction scenario before moving onto step 7 of the procedure. Then, fill out the “Actual" column as you complete steps 8 and 9.

Reactants Prediction Actual
Bleach (E) and Hydrogen Peroxide (D) pH of product:

Will product be acidic, basic, or neutral?

pH of product:

Was product acidic, basic or neutral?

 

Baking Soda (A) and Lemon Juice (C) pH of product:

Will product be acidic, basic, or neutral?

pH of product:

Was product acidic, basic or neutral?

 

Baking Soda (A) and Vinegar (B) pH of product:

Will product be acidic, basic, or neutral?

pH of product:

Was product acidic, basic or neutral?

 

The Reactions of Acids and Bases Activity:

Students record their predictions and results of the lab activity. Once the activity is finished, discuss the lab activity and answer post-lab questions.

We also provided some of the Resources below for you to use in class. iTeachly Members can access all the content for the activity and the following lesson.

Students must come up with a unanimous answer for each question. Discussing the answers usually, results in some excellent dialogue on this topic.

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Reactions of Acids and Bases - PDFs

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