Acid/Base pH
Name: _________________________________________ Page 1 of 7
Experiment: Properties of Acids and Bases
(Do a data table in Word and email the file to me.)
PURPOSE: To determine the properties of strong
acids and bases.
Partner “1” write observations for HCl
& KOH. Partner “2” write observations
for H2SO4 & NaOH
PROCEDURE:
1. Test 1M HCl with red and blue litmus paper, and
with phenolphthalein, bromthymol blue, and
methyl red indicators. Design a data table for this lab.
2. Test 1M HCl for electrical conductivity. Hand-held conductivity testers is in the cardboard box on the right
hand side of the room.
3. Put a 3 cm long magnesium metal strip into 1M HCl in a test tube. Collect the gas given off by inverting a
test tube over the mouth of the reaction tube. Test the gas with a burning splint. Be sure to hold both test
tubes with test tube clamps. Include a diagram of the set up in your lab report. Write the equation for the
reaction.
Caution: If you are afraid of
loud noises, let your partner hold
the test tubes.
4. Test 1M H2SO4 as you did HCl in steps 1, 2,
and 3. Write the equation for the reaction.
5. Test 1M NaOH with red and blue litmus
paper, and with phenolphthalein,
bromthymol blue, and methyl red indicators.
6. Test 1M NaOH for electrical conductivity
7. Rub a bit of the 1M NaOH between your
fingers (rinse immediately).
8. Test 1M KOH as you did NaOH in steps 5-7.
Acid/Base pH
Name: _________________________________________ Page 2 of 7
Partner 1 do a, b, e
Partner 2 do c, d, f
Experiment pH
Data table and analysis. Can be done as a
Paper/Pencil lab (handwritten).
Work these problems before beginning the lab.
10.4 Calculating [H+] or [OH-] of a Weak Acid or Base (You may have to ask me to explain Ka
and Kb and the importance of the number.
To calculate the [H+] and the pH for vinegar which is 0.10M HC2H3O2 (CH3COOH), first write the
equilibrium equation: HC2H3O2(aq)
C2H3O2-(aq) + H+(aq)
Then write the equilibrium expression, and look up to Ka value:
Ka = 1.8 x 10-5 = [C2H3O2-] [H+]
[HC2H3O2]
Record concentration of each substance before the acid ionizes and after it ionizes:
Before the Acid Ionizes
[HC2H3O2] =0.10M
[C2H3O2] = 0
[H+] =0
After the Acid Ionizes
[HC2H3O2] = 0.10 - x
[C2H3O2-] = x
[H+] = x
x is the amount of acid that ionizes. Since the mole to mole ratio is 1:1:1, if “x” moles of HC2H3O2 ionize,
“x” of C2H3O2- and “x” of H+ will be formed. Since the Ka value is so small, you know that “x” is very, very
small, so the concentration of HC2H3O2 does not change enough to be mathematically significant.
Therefore [HC2H3O2] = 0.10 - x = 0.10.
[x]
[x]
Ka = 1.8 x 10-5 = [C2H3O2-] [H+] = x2
[HC2H3O2]
0.10
x = 1.3 x 10-3M = [H+]
pH = - LOG 1.3 x 10-3 = 2.9
A5 Do All Homework
Self Test 10.4 SHOW YOUR WORK
1. Calculate the pH for a solution of 0.10M HNO3 (ionizes 100%). (2 pts)
2. Calculate the [H+] and pH for a solution of 0.10 M HF (Ka = 6.8 x l0-4). Note the difference in pH between
this weak acid and the strong acid in problem one even though they have the same molarity. (5 pts)
3. Calculate the [OH-], the pOH, and the pH of a solution of 0.25M NH4OH (Kb = 1.8 x 10-5). (5 pts)
Acid/Base pH
Name: _________________________________________ Page 3 of 7
Purpose: Use the pH probe and Logger Pro Program or pH paper. Set up a data table that shows the
calculations.
Procedure: (see me to help you with the volumetric flask)
1. Before coming to class, calculate how to prepare the following solutions:
a) 100.0 mL of 0.01M HCl from a 1.0M solution of HCl (ionizes 100%)
b) 100.0 mL of 0.0010M HCl using the 0.010M solution of HCl (ionizes 100%)
c) 100.0 mL of 0.010M NaOH from a 1.0M solution of NaOH (ionizes 100%)
d) 100.0 mL of 0.0010M NaOH using the 0.010M solution of NaOH (ionizes 100%)
e) 100.0 mL of 0.010M HC2H3O2 using the 1.0M solution of HC2H3O2 (Ka = 1.8 x 10-5)
f) 100.0 mL of 0.010M NH4OH using the 1.0M solution of NH4OH (Kb 1.8x 10-5)
Both - Do this for your solutions.
2. BOTH—Prepare the solutions. Calculate and test the pH values of these solutions. Compare the experiment
values to the calculated pH values.
3. Calculate the % Error. ORGANIZE THE MATERIALS SO IT IS EASY TO FIND! Use a data table.
4. Notes: MwVw = MsVs
More pH
(Wiki page)
Partner 1 do HCl Partner 2 do NaOH
Purpose: To understand pH better.
Procedure:
1. Starting with a 1.0M solution of HCl, make a serial dilution by pipetting one mL of the 1.0M HCl into
nine mL of water (use a pipet for the nine mL of water), and stir. Calculate the molarity of this solution. Show
work
2. Now take one mL of the 0.10 HCl, and add it to nine mL of water, and stir. Calculate molarity of this
solution. Show Work
3. Continue the dilution until you have 1.0 x 10-6 M HCl. Show work.
4. Predict the pH of each solution, and test with a pH meter. Show work.
5. Repeat the experiment starting with 1.0 M NaOH.
6. Molarity =
moles of solute
1 L or 1000 mL of solution
If I dilute a solution with enough water to double its volume then its molarity is halved. It is half as
strong as it was. Show Sample calculations on lab report and have a data table to show results of
calculations. Set up a data table that shows the number of mL of each concentration added to 9 mL, the
resulting molarity, predicted pH, measured pH and % Error. Show sample calculations in the analysis.
Do a wiki page. Your final lab report should have a title, purpose, an extensive data table,
a sample of each calculation, and a conclusion podcast or video that discusses the patterns
you should have observed. If you use video, you can use the Promethean board to project
your data table and video your discussion.
Acid/Base pH
Name: _________________________________________ Page 4 of 7
Experiment: pH and Indicators (email)
Partner 2 do NaOH Partner 1 do HCl
Purpose: To see the effects of pH on an indicator.
Procedure: Have your teacher supervise and sign to indicate you completed the lab. Set up a data table with the
results shown.
1. Do a serial dilution by adding one drop of 1M HCl and 9 drops of HOH to make 0.1M HCl, stir with a
toothpick. Take one drop of the 0.1M HCl, and add 9 drops of HOH to make the 0.01M HCl. Continue. Add
indicators to each well, and record the colors of the indicators.
2. Do the same for NaOH.
3. Test the unknown and report the molarity of the unknown.
Plastic Well Plate
A coloring sheet is not an appropriate lab report for this lab. You can use a coloring sheet as part of the lab but
a discussion of your observations is mandatory for this lab. Why did you observe what you did when you did
the lab? Take a picture or video your experimental results. I have a video camera most of the time you can use.
Email
Acid/Base pH
Name: _________________________________________ Page 5 of 7
Acid Rain (Partner 1: do Part A &B. Partner 2: do Part C & D) (Email)
Prepared by: James A. Skipper, East Mississippi Community College
Purpose: You are to learn about causes of acid rain and how we can detect and identify the gaseous
molecules responsible.
Discussion:
In this lab, you will investigate the effect of acid anhydrides on the waters of the earth. Acid anhydrides are
nonmetal oxides such as NO2, CO2, and SO3 that react with water to form acids. You will model clouds,
rain, natural lakes and other water sources.
One of the major sources of acid rain and smog (acid fog) is the automobile. Internal combustion engines
produce nitrogen oxides. By compressing air (nitrogen and oxygen) in combustion chambers (cylinders) at
high temperatures, the nitrogen and oxygen react to form NOx's nitrogen oxides. Since several nitrogen
oxides are possible, we refer to them collectively as NOx's. Nitric oxide, NO, is the most common to be
formed initially but it rapidly reacts to form nitrogen dioxide, NO2 which dissolves in water to form nitric
acid. Nitric acid dissociates to form nitrate ions, NO3-, which are used by plants as fertilizer for making
proteins.
Another source of nitric oxide and thus nitric acid in the water cycle is lightning. Lightning breaks oxygen
and nitrogen molecules. The fragments may reassemble to form ozone and nitric oxide.
Another major cause of acid rain and smog is the burning of sulfur – containing fuels such as wood, oil and
coal. Sulfur oxidizes to form sulfur dioxide gas. Sulfur dioxide undergoes further oxidation to form sulfur
trioxide. Sulfur trioxide dissolves and reacts with water to form a dilute solution of sulfuric acid, a very
strong acid. Strong acids dissociate in water almost completely. If sulfuric acid forms, we should be able to
identify the sulfate ion in solution.
Acid rain is natural and is a part of the nitrogen cycle, and the sulfur cycle. Without it, the land would
become depleted of nutrients that plants need and life would cease. The problem is that in some parts of the
world man's activities have increased the amount of acid forming gases to the point that environmental
damage is being done by acid rain.
In this lab we will generate NOx's and SO2 to simulate the formation of acid rain and smog. We will create
model lakes to see the effects of these gases on the Earth's waters We will use bromcresol green (BCG) as
an indicator to observe pH changes, a mixture of starch and iodide ions to observe oxidation and use
barium ions to detect the sulfate ion.
Materials:
2 M H2SO4 (sulfuric acid)
0.5 M Na2SO3 (sodium sulfite)
0.5 M KNO2 (potassium nitrite)
0.0l MNaHCO3 (sodium bicarbonate)
KI/ starch indicator
BaCl2 (barium chloride)
BCG (bromcresol green) indicator
NaOCl (sodium hypochlorite or " bleach")
2M NH3 (ammonia)
6M HCl (hydrochloric acid) 2 plastic Petri dishes clear plastic cup
Acid/Base pH
Name: _________________________________________ Page 6 of 7
Safety: You will be using very small quantities of ammonia (an irritant) and acids (corrosive). You should
wear safety glasses. If you get any on yourself, wash it off with water. Keep the lid closed on the Petri
dishes after you start generating gases. Because some of these gases are toxic, minimize your exposure to
the gases produced even though the quantities are small.
Disposal of Waste: Neutralize acids with ammonia or sodium hydroxide then discard in waste container.
Iodine should be reduced to its colorless from with sodium thiosulfate.
Reference: Chemtrek Small Scale Experiments for General Chemistry by Dr. Stephen Thompson,
Chapter 16, Prentice Hall.
Procedure
You are to record your observations and your interpretation of the reactions you observe in you laboratory
notebook. Keep good notes.
Part A: A Probe System to Detect Acidity and Alkalinity We cannot see molecules directly but we can
detect them and interpret what they are doing by using indicators or "probes."
Use clean dry Petri dishes as your containers for these tests. Colors can be best seen against a white
background. White precipitates and gas bubbles can be best seen against a black background. Use both
types of backgrounds.
1. Place a drop of BCG indicator on the dish
2. Add a drop of H2SO4 close by? Observation? Interpretation? No effect, right?
3. What is the effect of H2SO4 on BCG? Try it and see. Add a drop of BCG to a drop of sulfuric acid.
4. What is the effect of H2SO4 on BaCl2? Add a drop of one to the other. When you are looking for a white
precipitate latter in this experiment, it will not form that fast nor will it be that white.
5. Add a drop of ammonia close to a drop of BCG and cover. Explain what you think is happening. Do not
allow ammonia to mix with chlorine gas or chlorine bleach. They react to form chloroamine, a poisonous
gas.
6. In a clean dry Petri dish, add a drop of bleach then add a drop of starch/KI solution close by and cover.
Observe for two or three minutes. Chlorine gas, a powerful oxidizing agent, is released from chlorinated
water and from chlorine bleach (sodium hypochlorite). After observing the starch indicator for a minute
or more, add a drop of sulfuric acid to the bleach and cover quickly. What effect did the acid have on the
decomposition of the bleach? Add a drop of sodium sulfite to starch/KI mixture. Do you think sodium
sulfite is an oxidizing or a reducing agent?
Questions:
What do you think happens to the chlorine which is added to our water supplies (swimming pools,
drinking water) to disinfect the water?
How do you detect an acid? A base? An oxidizing agent? A reducing agent? The sulfate ion?
Write a paragraph about observations and conclusions.
Acid/Base pH
Name: _________________________________________ Page 7 of 7
Part B: Nitric Oxide and its Effect on Water You are to generate an environmental pollutant, detect
it, observe some of its properties then safely dispose of it. The gases generated are toxic but are
produced in small quantities and contained within an environmental chamber (Petri dish). You will
generate nitric oxide by reacting sulfuric acid with potassium nitrite.
1. Add 1 drop of potassium nitrite to the center of the dish.
2. Add 2 drops of BCG about 1 inch from the center of the dish.
3. Add 2 drops of Starch/KI solution the same distance on the other side.
4. When you are ready for the reaction to start, add 2 drops of sulfuric acid to the potassium nitrite and
cover quickly.
5. Now add 2 drops of ammonia to the dish. Allow it to diffuse as a gas. Ammonia helps neutralize acid
in the atmosphere. Observations? Interpretations?
6. Now add a drop of sodium sulfite directly to the starch/iodide complex. Sodium sulfite is a reducing
agent. Iodine is toxic in its oxidized form but harmless in its reduced form. Why did you add the
sodium sulfite before discarding?
7. Discard the waste into the plastic tray (waste container), then rinse and dry your Petri dishes.
8. Write a paragraph of observations and conclusions.
Part C: The Effect of ______ on pH Changes in Surface Water. You are to apply what you learned
and design experiments to test the effects of some of these variables. Site visual evidence to each.
1. What is the effect of distance from the pollution source on the rate at which the model lakes become
acidic?
2. What is the effect of the surface area? Make a big lake with 3 drops of BCG, and then make 3 onedrop "lakes." Compare the rate of color change in the two areas.
3. What is the effect of the size of the lake? Compare the rate at which small lakes become acidic to
large lakes.
4. What is the effect of buffers (use sodium bicarbonate) on the rate the lake becomes acidic.
5. Write a paragraph about observations and conclusions.
Part D: The Effect of Sulfur Dioxide on Rain, Fog, Clouds and Lakes. In this activity, sulfur dioxide
will be generated and studied.
In the center of a clean dry Petri dish, add 1 drop of sodium sulfite then place the following indicators
approximately equidistance from the pollution source: (a) 2 drops of BCG, (b) 2 drops of
starch/potassium iodide, (c) 2 drops of barium chloride and (d) a drop of barium chloride & a drop of
diluted bleach or hydrogen peroxide. In the last indicator, if sulfur dioxide is absorbed, the chlorine or
hydrogen peroxide should oxidize it to sulfur trioxide. Sulfur trioxide reacts with water to form sulfuric
acid. The sulfate ion, if present, should react with the barium ion to form a white precipitate.
When you are ready for the reaction to begin, add 2 drops of sulfuric acid to the sodium sulfite and
cover.
Add 2 drops of ammonia near the sodium sulfite.
Did the sulfur dioxide oxidize the iodide ion? Is there evidence that the sulfate ion formed? What was
the purpose of have 2 barium chloride solutions?
Email a paragraph about this lab