Conductivity Lab

Purpose (put into lab book)

• The purpose of this lab is to examine how the concentration of an acid affects the conductivity of the acid. We will also determine which acid, hydrochloric acid or acetic acid, is better at conducting electricity.

Background (read the following information then answer the questions in complete sentences in your lab notebook)

In this experiment, you will examine conductivity using a conductivity probe. Conductivity is the ability to conduct electricity. We learned that both strong and weak acids break into ions when dissolved into water. Ions are what give a solution the ability to conduct electricity. When the probe is placed in a solution that contains ions, an electrical current is completed across the electrodes that are located on either side of the hole near the bottom of the probe. This results in a conductivity value that can be read by the computer. The unit of conductivity used in this experiment is μS/cm. The size of the conductivity value depends on the ability of the aqueous solution to conduct electricity. The higher the value, the better it conducts.

1. What is conductivity?

2. What device will you be using to measure the conductivity of the acid?

3. What gives solutions the ability to conduct electricity?

4. What unit is conductivity measured in for this experiment?

5. Draw a picture and write an equation to show what happens to hydrochloric acid when it dissolves in water.

6. Draw a picture and write an equation to show what happens to acetic acid when it dissolves in water.

Hypothesis (answer in complete sentences in lab book)

• 1. Which acid do you think will have a higher conductivity, hydrochloric acid or acetic acid?

1. How do you think the conductivity will be affected as the concentration of the acid is decreased?

Materials (put in lab book)

• Read the procedure below and list all of the materials required to complete this part of the lab. Do not forget to include chemicals and glassware.

Procedure

(Read Part 1 and draw a diagram explaining what you will be doing. - SHOW ME BEFORE MOVING ON!)

Part 1 - Preparing Diluted Solutions: FOLLOW DIRECTIONS CAREFULLY!!

(one lab group will do HCl, the other lab group across from you will do HC₂H₃O₂)

• 1. Measure out 100mL of 0.5 M HCl (or HC₂H₃O₂) and put it in the 0.5 M labeled beaker.

1. Take that beaker labeled 0.5 M from step 1 and measure out 20mL of that 0.5 M acid. Fill the 100mL graduated cylinder the rest of the way with water (80mL) and pour it all into the beaker labeled 0.1 M.

2. Now take the beaker from step 2 labeled 0.1 M and measure out 20mL of that 0.1 M acid. Fill the 100mL graduated cylinder the rest of the way with water (80mL) and pour it all into the beaker labeled 0.02 M

3. Now take the beaker from step 3 labeled 0.02 M and measure out 20mL of that 0.02 M acid. Fill the 100mL graduated cylinder the rest of the way with water (80mL) and pour it all into the beaker labeled 0.004 M.

4. STOP HERE AND MAKE THE SOLUTIONS FOR PART 1. WHEN YOU ARE FINISHED CONTINUE ON TO PART 2.

(Read Part 2 and draw a diagram explaining what you will be doing. - SHOW ME BEFORE MOVING ON!)

Part 2 - Measuring the Conductivity of Each Solution:

1. Hook up the conductivity probe to the computer and open LoggerPro.

2. Make sure the conductivity probe's switch is set to the range of 0-20000 μS.

3. Line the HCl (or HC₂H₃O₂) solutions up from highest to lowest concentration according to molarity.

4. Click the green collect button towards the middle of the tool bar of LoggerPro.

5. Dip the probe into the highest concentration solution and hold for 15 seconds.

6. Move it to the next solution and repeat all the way to the lowest concentration solution.

7. When you have gone through each HCl (or HC₂H₃O₂) solution hit the red stop button located towards the middle of toolbar in LoggerPro.

8. Autoscale your graph.

9. Using your mouse, highlight the first plateau of your graph.

10. On the top toolbar click "Statistics" and a box will appear. Record the max value given in the box.

11. Repeat for each plateau.

12. Now trade the solutions you prepared with the other side of the desk and measure the conductivity of their solution.

Data (put into lab book)

Click here if you're absent to see pictures from lab.