PLEASE
Remember to do this in DARK BLUE OR BLACK INK. You may not write over pencil.
Answer all analysis questions on your own. If you have questions, please ask me.
For any question requiring an explanation, please put it in a complete sentence.
Electrolytes Lab
Objectives
 Observe and record the electrical conductivity of water solutions and solid compounds.'
 Classify substances as strong electrolytes, weak electrolytes or nonelectrolytes using
conductivity data.
Introduction
Electrolytes are compounds that exist as dissolved ions in water solutions. A distinguishing macroscopic
property of electrolyte solutions is that they conduct electricity. Molten electrolytes also conduct
electricity. The submicroscopic interpretation is that the ions are free to move about in the liquid, and
these charged particles carry the electrical current.
Purpose
In this experiment you will investigate water solutions of chemicals by testing them for conductivity. .
You will interpret your results in terms of the submicroscopic behavior of atoms and molecules. Finally,
you will test various solutions to determine their relative tendencies to conduct electricity, and again
interpret you results based on what the electrons, atoms, and molecules are doing. You will classify
solutions as strong electrolytes (those that readily conduct electricity); weak electrolytes (those that
conduct electricity only weakly); and nonelectrolytes (those that do not conduct electricity).
When the two leads are immersed in a drop of solution or in a solid that conducts electricity, the light
emitting diode (LED) will glow.
Safety




Wear your safety goggles
Use only full small-scale pipettes on for the carefully controlled delivery of liquids.
Do not drop the pipette on the bulb; it could cause the chemical to splash.
If you are using acetone, be aware that it will remove nail polish.
Materials
Small-scale pipettes of the following solutions and solids:
Solutions:
methanol (CH3OH)
water
ethanol
2-propanol
hydrogen peroxide(CH3CH2OH) or
(CH3CHOHCH3)
Solids and solutions
sodium chloride
sodium carbonate
potassium iodide
potassium chloride
Acetone
CH3COCH3
calcium chloride
sucrose
PLEASE
Remember to do this in DARK BLUE OR BLACK INK. You may not write over pencil.
Answer all analysis questions on your own. If you have questions, please ask me.
For any question requiring an explanation, please put it in a complete sentence.
Equipment:
Small-scale reaction surface
conductivity apparatus
small cup with distilled water for rinsing electrodes
EXPERIMENT
Wear your goggles.
Wear an apron. Follow all safety rules.
Record your observations on the sheet that says EXPERIMENTAL DATA.
Part A. Conductivity of Ionic Compounds
1. To test the compound dry, place 1 grain of each solid in the indicated place on the reaction surface
and test each for conductivity. To test the compound wet, use the DROPPER that says “distilled
water”; not your rinsing water. Add 1 drop of distilled water to each compound and test the “wet”
mixture.
- Write ALL your observations on the “Experimental Data” page.
1) Did the light go on and if so 2) was it strong or weak?
3) Did anything else happen?
NaCl(s)
KCl(s)
KI(s)
CaCl2 (s)
Na2CO3(s)
C12H22O11 (s)
salt
“lite” salt
un-iodized
salt
ice-melter
washing soda
table sugar
Part B. Conductivity of Liquids
2. Place 1 drop of each indicated chemical solutions bellow on the plastic sheet in the designated place
and test each drop for conductivity with the conductivity apparatus. Be sure to clean and dry the
conductivity leads after each test.
1) Did the light go on and if so 2) was it strong or weak?
3) Did anything else happen?
H2O (l)
water
CH3CH2OH (l)
Or CH3COCH3 CH3CHOHCH3(l)
ethanol (grain) or
acetone
2-propanol
rubbing alcohol
CH3OH (l)
methanol
(wood) alcohol
H2O2 (l)
hydrogen peroxide
a disinfectant
Cleaning up
Avoid contamination by cleaning up in a way that protects you and the environment. Careful clean the
reaction surface with a damp paper towel and dry the surface. Dispose of the paper towels in a trash
BAG, not in the trash can. You will be instructed to wash your hands. Put them completely under the
running water and rub them together. You do not need to use soap.
Turn In From this point to the end. Do not turn in the 1st 2 pages.
Name ______________________________________
Per ____________
Name_______________________________________
Name ______________________________________
Name ______________________________________
EXPERIMENTAL DATA
PART A
Write your, record your results for the tests done on the previous page.
YOU MUST HAVE ANSWER FOR AT LEAST 1 & 3. 1 & 2 can be just one word. 3 can be abbreviated if it is
understandable (Give a key).
1) Did the light go on and if so 2) was it strongly or weakly?
3) Did anything else happen?
NaCl(s)
KCl(s)
KI(s)
CaCl2 (s)
Na2CO3(s)
C12H22O11 (s)
salt
“lite” salt
un-iodized
salt
ice-melter
washing
soda
table sugar
1.
Observations
dry
2.
3.
Observations
“wet”
PART B
H2O (l)
CH3CH2OH (l)
or CH3COCH3
CH3CHOHCH3(l)
ethanol (grain) or
acetone
2-propanol
rubbing alcohol
CH3OH (l)
H2O2 (l)
Observations
water
methanol
(wood) alcohol
hydrogen peroxide
a disinfectant
Remember to do this in DARK BLUE OR BLACK INK. You may not write over pencil.
Answer all analysis questions on your own. If you have questions, please ask me.
For any question requiring an explanation, please put it in a complete sentence.
PLEASE
Questions for Analysis
Use what you learned in your observations to answer the following questions:
Answer any question that requires a written response (not a picture) in a complete sentence.
For these answers a weak glow is NOT a positive result – it does not
conduct electricity.
Describe how the electrolyte tester works including why it works on electrolytes and not on non-electrolytes.
(Include how the electricity travels, what is happening to the circuit when the light goes on and when it goes off.
What makes the electricity flow?)
A.
Which of the solids (no water added) in any part of this experiment conducted electricity?
B. What must be added to the solids before it will conduct electricity?
C. Does adding water make the substance conduct electricity every time? What substance(s) didn’t?
You can picture solid sodium chloride as a regular ordered arrangement of atoms called an ionic lattice. Solid
KCl and KI are similar to NaCl. Draw them and explain the result of the conductivity test of the solid versus
when water was added in terms of your drawing. In other words, explain why the same compound gave a
different result when tested as a solid and as a liquid using the drawing.
Using the drawings AND explain in words
why electricity flowed in the aqueous
forms but not in the solid forms. Use the
drawings you did in the boxes to the left
and this space to explain in words.
Solid NaCl
liquid NaCl
Solid KCl
liquid KCl
Solid KI
Liquid KI
Remember to do this in DARK BLUE OR BLACK INK. You may not write over pencil.
Answer all analysis questions on your own. If you have questions, please ask me.
For any question requiring an explanation, please put it in a complete sentence.
PLEASE
3. You know that solutions that conduct electricity do so because they contain ions that are free to move
about in solution. The picture below is an example of a solution of aqueous sodium chloride. Draw
pictures to represent the solutions of KI and KCl. Use another piece of paper if you do not have
enough room.
4. Which of the liquids in Part B conducted electricity? This is a list and does not need to be in a
sentence.
___________________________________________________________________________
___________________________________________________________________________
5. Make a list of the formulas for all the substances dissolved in water or liquids used in this lab that
electrolytes. (This does NOT need to be in a sentence.)
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
were
6. Make a list of the formulas for all of the non-electrolytes use in this lab. (This does NOT
need to
be in a sentence.)
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
7. Why is pure water (distilled) considered a non-electrolyte? ___________________________
___________________________________________________________________________
___________________________________________________________________________
8. Predict what will happen if you test tap water for conductivity and explain why. ___________
____________________________________________________________________________
____________________________________________________________________________
9. What is the characteristic of an electrolyte solution that allows it to conduct electricity?
___________________________________________________________________________
___________________________________________________________________________
10. Describe characteristic of the structure of the non-electrolytes that prevents them from conducting
electricity? _________________________________________________________________
___________________________________________________________________________
__________________________________________________________________________