NAME: ______DATE: ______

NEUTRALIZATION LAB

Introduction: In this lab, you will investigate a neutralization reaction when you mix an acid and a base together as shown in the general word equation below:

ACID + BASE  IONIC COMPOUND (SALT) + WATER

A neutralization reaction begins with acidic and basic reactants and results in two neutral products. To help with this investigation, you will be using an acid-base indicator called phenolphthalein. This indicator appears colourless when the solution is acidic and appears fuchsia (dark pink) when the solution is basic. A neutral solution will appear as a very faint pink colour.

By determining how many drops of base is required to neutralize known concentrations of acids, you will be able to determine the concentration of an unknown acid. Each group of students will be responsible for determining an unknown concentration of acid.

Safety: 1. Acids and Bases cause skin burns – Wash off skin with lots of water and clean up spills.

2. Wear goggles throughout the lab (whenever chemicals are at your desk or in your hands).

Materials: - HCl(aq) –100%, 50%, and 25% Concentrations - NaOH(aq) (In dropper bottle) - Unknown HCl(aq) solution (A, B, C, D, E, F, G, H, I, J) - Spot plate - Phenolphthalein (In dropper bottle)

Procedure: 1. At the front teacher’s work station:  Add 10 drops of an acid of known concentration to the corresponding well of the spot plate. (100% in well #1, 50% in well #2, and 25% in well #3) 2. At your work station – Add 1 drop of phenolphthalein indicator to well #1. 3. Using the dropper, add 1 drop of base to well #1. 4. Thoroughly mix the contents of the spot plate by gently swirling. 5. Repeat steps 3 and 4 until the solution turns and stays a pink colour. 6. Record the number of drops in your observation table. 7. Repeat steps 2-6 for all acids of known concentration (100%, 50%, 25%) 8. Add 10 drops of your Unknown acid concentration to well #4 and repeat steps 2-6. 9. Don’t forget to circle the appropriate letter to indicate which unknown acid you were assigned. 10. Clean the spot plate with water, dry it off, and return your materials to the front teacher bench. Observations:

Assigned Unknown Acid: A B C D E F G H I J

ACID Concentration 25% 50% 100% Unknown Letter: ______Volume of base (drops)

Lab QUIZ Next Class: Bring ruler and pencil!

Topics

1# Create a Graph 1. Create a hand-drawn graph plotting acid concentration (percent) versus volume of base (number of drops) for the 3 known acids. 2. Draw a line of best fit (concentration of acid varies directly with base). 3. Ensure your graph has a descriptive title and labeled axes with units. 4. Using your line of best fit, determine the concentration of your unknown acid. Show all work used to determine the concentration of acid.

2# Conclusion: What is the concentration of your unknown acid?

3# Questions: Be able to write a word equation and balanced chemical equation for the reaction. Explain the reactants and products in neutralization reactions. Why do antacids work?