IONS IN SOLUTION
ACIDS, BASES, AND SALTS
BIOLOGY
UNIT 1
NAME _________________________
TEACHER _______________________ HR _____
1
Ions in Solution – An introduction to Electrolytes, Acids, Bases and Salts
Definition of an ion:
__________________________________________________________________________________________________
1) ELECTROLYTES
a) Definition:
b) There are three types of electrolytes:
i)
ii)
iii)
c)
d) Example:
2) STRONG VS. WEAK ELECTROLYTES
a)
i)
ii)
3) CLASSIFICATION OF ELECTROLYTES (The Three Types)
a) Type 1: ACIDS
i)
Definition:
ii) Properties of acids:
(1)
(2)
(3)
(4)
2
iii) Common Acids:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
b) Type 2: BASES
i)
Definition:
ii) Properties of bases:
(1)
(2)
(3)
(4)
(5)
iii) Common bases
(1)
(2)
(3)
(4)
c) Type 3: SALTS
i)
Definition:
ii) Formed when…
iii) Properties of salts:
3
iv) Common salts
(1)
(2)
(3)
(4)
4) pH
a) Definition:
b) pH Scale
0
1
2
3
4
5
6
7
8
9 10
11
12
13
14
c) pH strength:
Each step you move on the pH scale is a difference in strength by ________ time.
Example: A solution at pH 5 is 10 x more acidic than a solution at pH 6, and is 100 x more acidic than a
solution of pH 7.
pH of common substances:
Substance
Stomach Acid
Vinegar
Carbonated drinks
Human Blood
Sea Water
Household ammonia
1 M NaOH—concentrated sodium hydroxide
d) Indicators
i)
Examples:
(1)
pH
1.0 - 3.0
2.4 - 3.4
2.0 - 4.0
7.3 - 7.5
7.8 - 8.3
10.5 - 11.5
14.0
4
(2)
5) Neutralization:
6) The importance of electrolytes to living things:
5
Ions in Solution --Practice Exercise
(Use your notes to help you answer the following questions.)
1. What is an ion?
2. What are electrolytes and why can they conduct electricity when dissolved in a solution (like water)?
3.
What is the difference between a strong and a weak acid?
For each of the following, tell whether it refers to Acids (A), Bases (B), Salts (S), All (ALL) or None (NONE). Use your notes!
_______ 4. Releases ions when mixed with water
_______ 5. Is considered an electrolyte
_______ 6. Releases OH- when mixed with water
_______ 7. Formed when equal parts acid and a base are mixed
_______ 8. Taste sour
_______ 9. Conduct electricity when mixed with water
_______ 10. Has a pH above 7.
_______ 11. Releases ions in solution that are not H+ or OH_______ 12. NaOH is one of these.
_______ 13. Sugar is an example of this.
_______ 14. HCl is one of these.
_______ 15. MgCl2 is one of these.
_______ 16. Neutralizes bases
_______ 17. Reacts with mineral salts like CaCO3
_______ 18. Reacts with greases
6
19. Name two acids that are found in your body.
a.
b.
20. True or False? An acid is an electrolyte?
21. True or False? A salt is made by neutralizing an acid with a base?
22. True or False? Our drinking water has an approximate pH of 3.
23. When one of your classmates held onto the cattle prod, they acted as a conductor of electricity for the light bulb.
Using the information from the demonstration (and your notes), what allows humans to be able to conduct electricity?
24. Fill in the Venn Diagram below about Acids, Bases, and Salts.
Salts
Acids
Bases
7
Ions in Solution LAB – Acids, Bases, Salts, and Indicators
Purpose:
This investigation is designed to allow you to make observations about how various indicators look in the
presence of ions in acidic or basic solutions.
Safety:
YOU MUST WEAR GOGGLES AT ALL TIMES AND WASH YOUR HANDS THOROUGHLY
AFTER CLEANING UP YOUR LAB SPACE TODAY!
Materials:
Well tray, hydrochloric & acetic acids, sodium & ammonium hydroxide, various indicators.
Procedure:
Read the procedure outlined for each set-up at your table. You will be testing various indicators in acids
and bases. Indicators are substances that change color in acidic or basic solutions. Use the
data table on page 8 to record your data from today and answer questions about these solutions.
Set up:
1) Rinse out your well tray with warm water and shake upside down to empty.
2) Take a white sheet of paper and a plastic well dish. Place the white sheet of paper under the well
plate. Label the paper with the acids/bases you will be testing in wells A, B, C and D.
3) Place 2-3 drops of each acid OR base into the appropriately labeled well. (see below)
a. 1A-5A = hydrochloric acid: HCl
b. 1B-5B = acetic acid: H(C2H3O2)
Acids
c. 1C-5C = sodium hydroxide: Na(OH)
HCl H(C2H3O2)
d. 1D-5D = ammonium hydroxide: (NH4)(OH)
A
4) Using Litmus and pH paper to test for acids and bases:
a. Dip one half strip of RED litmus paper into each
well 1A-1D, and record the color change in the
data table.
b. Dip one half strip of BLUE litmus paper into each
well 1A-1D, and record the color change in the
data table.
c. Dip one half strip of pH paper into each well 1A1D, and record the color change on the chart on
page 49.
Note: You must compare the pH paper with the
standard colors listed on the pH paper container to
determine the pH value.
B
Bases
Na(OH) (NH4)(OH)
C
D
1
2
3
4
5
Acid/Base testing
plate
5) One by one, add 2-4 drops of each liquid indicator (numbers 1-5 from your chart) to each of the
acids/bases in the well. Note the color each indicator turned when in the acids and bases and write
your observations in the data chart.
6) When finished, be sure to thoroughly clean your well tray and wash your hands with warm soapy water.
8
Ions in Solution -- Laboratory Report Sheet
Procedure 1:
Record color changes you see when you use the following indicators for Procedure 1
Be sure to test the pH paper and the red and blue litmus papers first before you put the indicators into the wells.
Indicator
Color change
in HCL
(hydrochloric
acid)
Color change in Color change in
H(C2H3O2)
Na(OH)
sodium hydroxide
acetic acid
(base)
(vinegar)
Color change
in (NH4)(OH)
ammonium
hydroxide
(base)
1. Red cabbage juice
2. Phenolpthalein
(PPT)
3. Bromthymol blue
(BTB)
4. Turmeric
(Indian spice)
5. Universal indicator
6. pH paper—record
color and pH number
7. Blue litmus paperdoes it stay blue or
turn a color?
8. Red litmus paperdoes it stay pink or
turn a color?
Procedure 2:
Calcium oxide (CaO) is a metal oxide, because it is a compound made of a metal (Ca)
and an oxide (O-2).
Steps to follow: Put a drop of water on a clean glass plate. Now add some calcium oxide and pick an
indicator with an obvious color contrast in an acid or a base and determine if your
mixture is an acid or a base. (If you are unsure of the color, wait 5 minutes until the
mixture starts to dry, the color will be very evident.)
The indicator I used was ___________________. It turned the color _____________, which
means that CaO and H2O make a(n) ______________ and therefore the product in this reaction
must contain a(n) _______ ion.
9
Procedure 3:
CO2 (one of the gases you breathe out) is a non-metal oxide. Test CO2 for its pH.
Steps to follow: Obtain a 125 ml flask and fill it with 10-15 ml of distilled water. Then add 5 drops of BTB to the
water and swirl to mix.
a) Now take a clean straw and blow through it into the mixture. Explain how can you tell if your
breath is producing an acidic or basic environment in the solution.
b) Explain how you determined your answer to letter a above.
_____________________________________________________________________________________
Procedures 4 & 5: Teacher Demonstrations
Procedure #4: Your teacher will fill a beaker half full of water and add two drops of phenolphthalein to
the water. Watch carefully as sodium metal (Na) is added to the water and indicator
solution. How do you know if an acid or a base was produced?
Equation for this reaction:
Procedure #5: Your teacher will then add hydrochloric acid (HCl) to the beaker from #5 until the
solution turns clear. Two drops will be removed from the beaker and placed on a
microscope slide. This slide will be passed through a flame or heated on a hot plate
until the solution evaporates. What do you observe on the slide after the solution has
been evaporated?
Equation for this reaction:
10
Ions in Solution Review
1. What is an ion?
2. In your own words, define electrolyte:
3. What is the difference between a strong and a weak electrolyte?
4. Define the following and give an example of each:
a. Acid:
b. Base:
c. Salt:
5. Foods such grapefruit, sour cream or yogurt taste sour because they contain ___________.
6. What ion is produced by all acids, giving acids their properties? (If you’re stuck, look at the top picture on the
front cover of this packet.)
7. Name the strong acid that is produced in your stomach:
8. Why do you think most all of the foods we eat have a low pH?
9. Give the common name and formula (if you can) for three acids you would find at home or you use in your
daily activities.
a.
b.
c.
10. Give the common name and formula (if you can) for three bases you would find at home or you use in your
daily activities.
a.
b.
c.
11
11. What ion is produced by most bases and gives bases their properties? (If you’re stuck, look at the top picture
on the front cover of this packet.)
12. Name three characteristics of bases (make sure to include something about their pH):
13. On the pH scale below, label the numbers that represent acids, bases and neutral pH.
0
1
2
3
4
5
6
7
8
9 10
11
12
13
14
14. What is the difference (mathematically) between a pH of 5 and a pH of 6?
15. Complete the table by telling what color the following indicators would turn when they react with acids and
bases:
Indicator
PPT
Color in an Acid
Color in a Base
BTB
Universal indicator
Red cabbage juice
Red litmus
Blue litmus
Turmeric (Indian spice)
PH paper
16. Describe a situation in which the knowledge of the properties of acids, bases or salts would be beneficial to
you.