Chemistry
Acids and Bases
Century High School
Chemistry Instructors: Moertel, Stroh and Handlon
Name ___________________________________________Hour____
General Chemistry Standards Unit 10 Acids & Bases
I.
I can relate the properties of acids and bases to the ions they contain and
predict the products of an acid –base reaction.
A. I can identify whether a compound in solution would be an acid, base or salt given the
formula of the compound.
B. I can use the molarity of the solution to determine its pH and pOH.
C. I can predict the formula of a salt produced given the formulas of the acid and base being
then write a balanced equation for the neutralization reaction.
II.
I can determine the unknown molarity of an acid or base given the molarity and
volume of the other reactant and the volume of the sample.
A. I can use “titration data” and the definition of Molarity (Moles / Liter) to calculate the
molarity of an unknown acid or base solution.
1. For each of the following solutions state whether the solution is an acid or base and give the
pH & pOH.
Type of Solution
pH
pOH
a. 0.00001 M RbOH ________________
____________
_____________
b. 0.000001 M HF
________________
____________
_____________
c. 0.001 M NH4OH
________________
____________
_____________
2. Write the formula of the salt made by the reaction of the acid and base and then write a
balanced equation.
a.
KOH +
HNO3
b.
HBr
c.
H2SO4 +
Ca(OH)2
d.
LiOH
HCl
3.
Use the following lab data to determine the molarity (M) of the unknown. Show all work.
a.
The 25.0 ml sample of HCl required 15.0 ml of 0.30 M of NaOH to neutralize.
+
+
=
Mg(OH)2 =
=
=
__________
+
__________
_________
+
__________
_________
+
__________
_________
+
__________
Acid-Base Video Questions
1. Describe 2-3 chemical and physical properties of acids.
2. Describe 2-3 chemical and properties of bases.
3. How can someone determine if a solution which looks like water is acidic or
basic?
4. What happens when equal amounts of an acid and a base are mixed?
5. What ion is made by acids and what ion by bases?
6. What are the two main sources of acid rain?
7. What is the usual range of numbers for the pH scale? What are the acidic pH
numbers and what are the basic pH numbers? What is the pH of distilled water?
8. What is the pH of stomach acid? How does one counter excess stomach acid?
What kind of substance are these products?
Lab Activity: Acids and Bases
When solutes dissolve in water it can change the nature of the water. Some solutes in water make
solutions we call an acid, others make solutions we call a base. What kinds of compounds make acids in
water? What kinds of compounds make bases? What are some reactions and properties of acid and
base solutions? You will investigate these questions.
I. Acid – Base Indicators
1. Take out a piece of what is called red litmus paper.
2. Test each of the solutions (HCl, NaOH, KOH, HNO 3, H2SO4 and LiOH) with the red litmus paper.
Just touch the tip of the dropper to the red litmus paper. Write down the color change if the litmus
paper changes color.
3. Now test each of the solutions (HCl, NaOH, KOH, HNO 3, H2SO4 and LiOH) with the blue litmus
paper. Just touch the tip of the dropper to the red litmus paper. Write down the color change if the
litmus paper changes color.
4. Now test each of the solutions (HCl, NaOH, KOH, HNO 3, H2SO4 and LiOH) with the pH litmus
paper. Just touch the tip of the dropper to the red litmus paper. Compare the color of the paper with
the chart on the pH paper container and record the approximate pH of the solution.
Data Table Part I Acid Base Indicators
Formula of
Solution
Color Red
Litmus Paper
Color Blue
Litmus Paper
Color of pH
paper
pH of solution
1.
2.
3.
4.
5.
6.
II. Reactions of Acids & Bases
1. Into a small test tube measure 3 ml of the HCl. Have a piece of magnesium metal (Mg) ready to
drop into this. Light a wood splint and have it ready to test any gas produced by the reaction. Drop
the Mg into the HCl. Record your observations and test the gas produced by placing the wood splint
near the mouth of the test tube.
2. Dump out the HCl. Then repeat the reaction with 3 ml of HNO3. Test the gas made. Rinse out the
test tube.
3. Now in a separate test tube put Mg metal into 3.0 ml of NaOH. Is there a reaction? Keep any
unreacted metal but pour out the solution.
4. Repeat the process with 3.0 ml of KOH. Is there any reaction? Save any unreacted metal.
5. Into a small test tube measure 3 ml of the HCl. Light a wood splint and have it ready to test any
gas produced. Drop a small amount of sodium carbonate (Na2CO3) into the HCl. Record your
observations and test the gas produced by placing the wood splint near the mouth of the test tube.
6. Rinse the test tube then repeat the process with 3.0 ml of HNO3. Test any gas produced from this.
Data Table Part II Reactions of Acids & Bases
Formulas of Reactants
for that step number
Observations of Reaction
Results of burning splint test
Gas produced by
the reaction
1.
2.
3.
4.
5.
6.
Part III Electrical Conductivity of Water and Acids & Bases
Your teacher will add one of the solutions into the distilled water and demonstrate the conductivity.
Record whether the solution conducts (yes) or not (no) and whether that solution is an acid or base.
Combination With Distilled Water
1.
2.
3
4.
5.
6.
Conductivity (yes) or (no)
Type of Solution (Acid or Base)
Follow Up Questions
1. Which solutions were acids and which were bases? Give their names and formulas.
2. What ion do acids have in water and what ions do bases? What color does an acid turn litmus
paper and what color does a base?
3. Balance the chemical reactions that happened for Part II:
____ HCl + ___Mg
____MgCl2 +
___Mg + ___HNO3
____Mg(NO3)2 + ____ H2
___Na2CO3. + ___ HCl
___Na2CO3. + ___ HNO3
____H2
___ CO2 + ___H2O +
___CO2 + ___H2O +
___ NaCl
___ NaNO3
4. What happens to a burning splint when placed into hydrogen gas?
What happens to a burning splint when placed into carbon dioxide gas?
5. Will distilled water conduct electricity?
Which substances when put into distilled water conduct electricity (are “electrolytes”)?
6. What must be present or formed in water in order for it to conduct electricity?
DEFINING ACIDS & BASES
IDENTIFY THE FOLLOWING AS PROPERTIES OF ACIDS, BASES, OR BOTH. MARK THE APPROPRIATE BOX.
PROPERTY
ACID
BASE
BOTH
1. SLIPPERY
2. SOUR TASTE
3. STINGS OPEN WOUNDS
4. ELECTROLYTE
5. BITTER TASTE
6. OFTEN LOOKS LIKE PURE WATER
7. TURNS LITMUS FROM RED TO BLUE
8. HIGH PH (ABOVE 7)
9. TYPICALLY REACTS WITH METALS
10. TURNS LITMUS FROM BLUE TO RED
11. LOW PH (LESS THAN 7)
ANSWER THE FOLLOWING IN THE SPACE PROVIDED:
12. What is the ion in the formula of an acid? What is the ion in the formula of a base?
13. Give the name of four household products that are acids or bases and state whether it is an
acid or base.
pH & pOH Notes
1.
What is the range for the pH scale? What is the range for acidic pH? What pH is neutral? What
is always the total of the pH + pOH equal?
2. What does the prefix “p” in the terms pH or pOH mean? What is the definition of pH?
Steps To Finding pH & pOH
+
1. Examine the formula of the compound. If the compound has H in the formula then that
solution is an acid. This will give you the pH.
If the compound has OH in it then that compound is a base and will give you the pO
-X
2. Next write the concentration (Molarity) as a “power of ten as 1 x 10
places.
X = # of decimal
3. The positive number for X will be the pH if an acid or pOH if a base. Find the other by
subtracting the one you found from 14. pH + pOH = 14.
3. Determine the pH and pOH and pOH of the following:
A.
0.00001 M LiOH
B. 0.001 M HBr
C. 0.0000000000 M HF
D. 0.0000000 M KOH
E. 0.0000000000001 M HCl
F. pH = 5.4 then pOH = _________ Is this acidic or basic? ______________
G. pOH = 2.7 then pH = __________ Is this acidic or basic? ____________
Acid + Base Neutralization
Neutralize means “to cancel out”. In an acid + base neutralization equal amounts of an
acid plus a base cancel each other. The products are a “neutral” salt (ionic compound)
and water.
Acid + Base → Salt + Water
Acids are a solution of a compound with Hydrogen (H+) and a nonmetal ion or group (A-)
Bases are a solution of a compound of a metal ion usually from Group I (M+) and the
hydroxide ion (OH-)
In the neutralization the hydrogen ions (H+) react with the hydroxide ions (OH-) to form
HOH commonly known as water H2O.
The metal ion from the base (M+) combines with the nonmetal ion or group from the acid
(A-) to make an ionic compound MA (also called a “salt”).
In General terms:
HA + MOH → MA + HOH
Example:
HCl + NaOH → NaCl + H O
2
Balance the following neutralization reactions:
____HCl +
→
__Fe(OH)3
__FeCl3 + ___
___Mg(OH)2 + ___H2SO4 →
→
___NaOH + ___H2CO3
__Mg(OH)2 +__ HNO3 →
___KOH + ___H2SO4
____ H2SO4 +
____HBr +
__Ca(OH)2
→
2
____MgSO4 + ___ H2O
____Na2CO3 + ___ H2O
____Mg(NO3)2 + __H2O
→
__Al(OH)3
HO
____K2SO4 + ___ H2O
→
__Al2(SO4)3 + ___
__CaBr2 + ___
HO
2
HO
2
Titrations
1. What is a neutralization reaction?
2. What type of reaction is this?
3. What is titration?
4. What is a burette?
5. What is a titrant?
6. What is the equivalence point?
7. What is an acid base indicator?
8. How can you tell when the endpoint of a titration has been reached?
9. If you are titrating an acid, what type of solution should go in the burette?
LAB ACTIVITY: ACID & BASE TITRATION
Acids and Bases “neutralize” each other. This means that they “cancel” their chemical reactivity. Acids
and Bases are “opposite” in their chemical properties. They will cancel if the number of moles of acid
equals the number of moles of base. This is like having + 5 added to – 5 become 0. A +5 will not
cancel a + 2 because the numbers are both positive. A + 5 will not cancel a – 7 because the + 5 is too
small a positive number. But equal moles of acid and base will cancel.
An acid –base titration is a laboratory technique used to find the unknown concentration (Molarity) of
either an acid or base by reacting the unknown with an opposite solution of known molarity. In this lab you
will use 0.5 M NaOH to neutralize 10.0 ml samples of HCl in Part I and vinegar (acetic acid) in Part II.
You will use your data to calculate the molarity of the two acids.
Part I Titration of HCl
1. Make sure the burette has at least 25.0 ml of 0.5 M NaOH in it. You may adjust the level to make
the reading at a whole number. YOU MUST WEAR GOGGLES WHEN WORKING WITH ACIDS
AND BASES!
2. Record the initial volume of NaOH in the burette in your data table.
3. Measure 10.0 ml of the HCl into a small rinsed Erlenmeyer flask.
4. BE SURE TO ADD 2-3 DROPS OF THE PHENOLPHTHALEIN INDICATOR TO THE ACID IN
THE FLASK.
5. Slowly begin the titration. Swirl flask occasionally. As pink color begins to show, start adding
drop by drop until the color remains after swirling. Use a sheet of white paper to help see the
pink color.
6. Carefully record the burette reading of NaOH when the acid has been neutralized and the pink
color stay.
7. Now repeat the titration with a fresh sample of 10.0 ml of HCl. A different person should do this
trial. This time you will have an idea of where the endpoint might be. If the second trial is more
than 0.5 ml different from the previous trial do a third trial. Record all data in the table.
Part I Titration of Acetic Acid in Vinegar.
1. Make sure the burette has at least 25.0 ml of 0.5 M NaOH in it. You may adjust the level to make
the reading at a whole number. YOU MUST WEAR GOGGLES WHEN WORKING WITH ACIDS
AND BASES!
2. Record the initial volume of NaOH in the burette in your data table.
3. Measure 10.0 ml of the Vinegar into a small rinsed Erlenmeyer flask.
4. BE SURE TO ADD 2-3 DROPS OF THE PHENOLPHTHALEIN INDICATOR TO THE ACID IN
THE FLASK.
5. Slowly begin the titration. Swirl flask occasionally. As pink color begins to show, start adding
drop by drop until the color remains after swirling. Use a sheet of white paper to help see the pink
color.
6. Carefully record the burette reading of NaOH when the acid has been neutralized and the pink
color stay.
7. Now repeat the titration with a fresh sample of 10.0 ml of vinegar.. A different person should do
this trial. This time you will have an idea of where the endpoint might be. If the second trial is
more than 0.5 ml different from the previous trial do a third trial. Record all data in the table.
Data Table Part I Titration of HCl
Trial 1
Trial 2
Trail 3 (optional)
Trial 2
Trail 3 (optional)
Volume of HCl titrated
Start volume NaOH
End Volume NaOH
Volume of NaOH used
Data Table Part I Titration of Vinegar
Trial 1
Volume of Vinegar
titrated
Start volume NaOH
End Volume NaOH
Volume of NaOH used
Post Lab Calculations Part I:
1. Write a balanced equation for the reaction of HCl with NaOH. Write the names of the products.
What is the mole ratio?
2. Determine the average volume of 0.5 M NaOH used for the two or three trials of the titration of
HCl.
3. Calculate the moles of NaOH needed to neutralize the HCl sample. Remember Molarity =
Mole/Liters and also Moles = Molarity x Liters. The molarity of the NaOH in the burette was 0.5
M. Use your average volume in Liters.
4. What is the mole ratio of the HCl and NaOH? Using this ratio how many moles of acid were in
the 10.0 ml HCl? Remember when a base neutralizes an acid there are equal moles of each.
5. Use the moles of HCl and volume of HCl (10.0 ml) to calculate the Molarity of the HCl. Molarity =
Moles / Liters.
Post Lab Calculations Part II:
1. Balance the equation for the reaction of Acetic acid (HC2H3O2) with NaOH. What is the mole
ratio?
HC2H3O2 +
NaOH = NaC2H3O2 +
H2O
2. Determine the average volume of 0.5 M NaOH used for the two or three trials of the titration of
HCl.
3. Calculate the moles of NaOH needed to neutralize the vinegar sample. Remember Molarity =
Mole/Liters and
also Moles = Molarity x Liters. The molarity of the NaOH was 0.5 M. Use your average volume
in Liters.
4. What is the mole ratio of the Acetic Acid and NaOH? Using this ratio how many moles of acid
were in the 10.0 ml
HCl? Remember when a base neutralizes an acid there are equal moles of each.
5. Use the moles of Acetic Acid and volume of Acid (10.0 ml) to calculate the Molarity of the Acid.
Molarity = Moles / Liters.
Follow up Question:
A 25.0 ml sample of KOH was titrated with 0.1 M HBr. It took 10.0 ml of HBr to neutralize the sample.
Write the balanced equation for the reaction. Then use the Molarity and volume of the acid with the
volume of the base sample to find the Molarity of the Base. Show all work.