Part 1 - Get a Lab Appointment and Install Software:
Set up an Account on the Scheduler (FIRST TIME USING NANSLO):
Find the email from your instructor with the URL (link) to sign up at the scheduler.
Set up your scheduling system account and schedule your lab appointment.
NOTE: You cannot make an appointment until two weeks prior to the start date of this lab assignment.
You can get your username and password from your email to schedule within this time frame.
Install the Citrix software: – go to http://receiver.citrix.com and click
download > accept > run > install (FIRST TIME USING NANSLO).
You only have to do this ONCE. Do NOT open it after installing. It will work automatically when you go
to your lab. (more info at
http://www.wiche.edu/info/nanslo/creative_science/Installing_Citrix_Receiver_Program.pdf)
Scheduling Additional Lab Appointments:
Get your scheduler account username and password from your email. Go to the URL (link) given to you
by your instructor and set up your appointment.(more info at http://www.wiche.edu/nanslo/creativescience-solutions/students-scheduling-labs)
Changing Your Scheduled Lab Appointment:
Get your scheduler account username and password from your email. Go to http://scheduler.nanslo.org
and select the “I am a student” button. Log in to go to the student dashboard and modify your
appointment time. (more info at http://www.wiche.edu/nanslo/creative-science-solutions/studentsscheduling-labs)
Part 2 – Before Lab Day:
Read your lab experiment background and procedure below, pages 1-10.
Submit your completed Pre-Lab 1 Questions (page 6) per your faculty’s instructions.
Submit your completed Pre-Lab 2 Questions (page 7) per your faculty’s instructions.
Watch the Titration Apparatus Control Panel Video Tutorial
http://www.wiche.edu/nanslo/lab-tutorials#titration
Part 3 – Lab Day
Log in to your lab session – 2 options:
1)Retrieve your email from the scheduler with your appointment info or
2) Log in to the student dashboard and join your session by going to http://scheduler.nanslo.org
NOTE: You cannot log in to your session before the date and start time of your appointment. Use
Internet Explorer or Firefox.
Click on the yellow button on the bottom of the screen and follow the instructions to talk to your lab
partners and the lab tech.
Remote Lab Activity
SUBJECT SEMESTER: ____________
TITLE OF LAB: Buffers
Lab format: This lab is a remote lab activity.
Relationship to theory (if appropriate): In this lab you will learn the underlying principles on
how biological systems maintain pH within a narrow range is important to understanding the
function of these systems.
Instructions for Instructors: This protocol is written under an open source CC BY license. You
may use the procedure as is or modify as necessary for your class. Be sure to let your students
know if they should complete optional exercises in this lab procedure as lab technicians will not
know if you want your students to complete optional exercise.
Instructions for Students: Read the complete laboratory procedure before coming to lab.
Under the experimental sections, complete all pre-lab materials before logging on to the
remote lab, complete data collection sections during your on-line period, and answer questions
in analysis sections after your on-line period. Your instructor will let you know if you are
required to complete any optional exercises in this lab.
Remote Resources: Primary – Titration Apparatus; Secondary – Acetic Acid Titration
CONTENTS FOR THIS NANSLO LAB ACTIVITY:
Learning Objectives.................................................................................................... 2
Background Information ........................................................................................... 2-6
Pre-lab Exercise 1: Adding an Acid to Buffered Solutions ....................................... 6
Pre-lab Exercise 2: Adding a Base to Buffered Solutions ........................................ 7
Equipment ................................................................................................................. 7
Preparing for this NANSLO Lab Activity .................................................................... 7-8
Experimental Procedure ........................................................................................... 8
Exercise 1: Adding an Acid to Buffered Solutions .................................................... 8-9
Exercise 2: Adding a Base to Buffered Solutions ..................................................... 9
Summary Questions .................................................................................................. 10
Creative Commons Licensing .................................................................................... 10
U.S. Department of Labor Information ..................................................................... 10
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LEARNING OBJECTIVES:
After completing this lab, you should be able to:
1.
2.
3.
4.
5.
Define buffer, acid, and base.
Define pH and describe how the pH of a solution is measured.
Explain the effect of acids and bases on the pH of a buffered liquid.
Distinguish between acidosis, alkalosis, and the etiology of the different types.
Explain the role of the buffering systems inside our body in the prevention of acidosis
and alkalosis.
6. Compare the buffer stabilizing effect of 3 different solutions.
7. Collect and analyze data using a drop counter and digital pH probe.
8. Interpreting the data on a graph to determine the point at which buffer stabilization
fails.
BACKGROUND INFORMATION:
Buffer is a solution usually containing an acid and a base, or a salt that tends to maintain a
constant hydrogen ion concentration. Ions are atoms or molecules that have lost or gained one
or more electrons. An example of a common buffer is a solution of acetic acid (CH3COOH) and
sodium acetate. In water solution, sodium acetate is completely dissociated into sodium (Na +)
and acetate (CH3COO-) ions. The hydrogen ion concentration of the buffer solution is given by
the expression:
+
[𝐻 ] = 𝐾𝑎
[𝐶𝐻3 𝐶𝑂𝑂𝐻]
𝐶𝐻3 𝐶𝑂𝑂−
in which Ka is the ionization constant of acetic acid and the expressions in brackets are the
concentrations of the respective substances. The hydrogen ion concentration of the buffer
solution is dependent on the relative amounts of acetic acid and acetate ion (or sodium
acetate) present, known as the buffer ratio. The addition of an acid or a base will cause
corresponding changes in the concentration of acetic acid and acetate ion, but as long as the
concentration of the added substances is small compared to the concentration of the individual
buffer components, the new hydrogen ion concentration will remain close to its original value.
By “close to”, we generally mean within a factor of 10 of the original value. So, if the buffer
starts with a hydrogen ion concentration of 1 x 10-7 M, then the buffer is still working as long as
the hydrogen ion concentration stays between 1 x 10-6 M and 1 x 10-8 M.
As acid is any substance that in water solution tastes sour, changes the color of certain
indicators (e.g., reddens blue litmus paper), reacts with some metals (e.g., iron) to liberate
hydrogen, reacts with bases to form salts, and promotes certain chemical reactions (acid
catalysis). Examples of acids include the inorganic substances known as the mineral acids—
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sulfuric, nitric, hydrochloric, and phosphoric acids—and the organic compounds belonging to
the carboxylic acid, sulfonic acid, and phenol groups. Such substances contain one or more
hydrogen atoms that, in solution, are released as positively charged hydrogen ions.
A Base is any substance that in water solution is slippery to the touch, tastes bitter, changes the
color of indicators (e.g., turns red litmus paper blue), reacts with acids to form salts, and
promotes certain chemical reactions (base catalysis). Examples of bases are the hydroxides of
the alkali and alkaline earth metals (sodium, calcium, etc.) and the water solutions of ammonia
or its organic derivatives (amines). Such substances produce hydroxide ions (OH-) in water
solutions.
pH is a quantitative measure of the acidity or basicity of aqueous or other liquid solutions. The
term, widely used in chemistry, biology, and agronomy, translates the values of the
concentration of the hydrogen ion—which ordinarily ranges between about 1 and 10-14 gramequivalents per liter—into numbers between 0 and 14 (see figures 1 and 2).
pH is defined as the decimal logarithm of the reciprocal of the hydrogen ion concentration, [H+],
in a solution:
+
𝑝𝐻 = −𝑙𝑜𝑔10 ([𝐻 ])
In pure water, which is neutral (neither acidic nor alkaline), the concentration of the hydrogen
ion is 10-7 gram-equivalents per liter, which corresponds to a pH of 7. Because of the
logarithmic relationship between concentration and pH, a buffer that keeps the hydrogen ion
concentration within a factor of 10 of the original value will keep the pH within a range of +/- 1
pH unit.
A solution with a pH less than 7 is considered acidic; a solution with a pH greater than 7 is
considered basic, or alkaline. Common tap water is often adjusted to a pH between 7 and 8,
because this reduces the corrosion of metal pipes in the plumbing system.
Figure 1: Relationship between p[OH] and p[H] (red = acid region, blue = basic region
pH Wikipedia http://en.wikipedia.org/wiki/PH_scale (accessed 06/30/2014).
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Figure 2: pH values of some common substances. pH Wikipedia
http://en.wikipedia.org/wiki/PH_scale (accessed 06/30/2014).
Acidosis is a condition in which there is too much acid in the body fluids.
The kidneys and lungs maintain the balance (proper pH level) of chemicals called acids and
bases in the body. Acidosis occurs when acid builds up or when bicarbonate (a base) is lost.
Acidosis is classified as either respiratory or metabolic acidosis.
Respiratory acidosis develops when there is too much carbon dioxide (an acid) in the body. This
type of acidosis is usually caused when the body is unable to remove enough carbon dioxide
through breathing. Causes of respiratory acidosis include: chest deformities, such as kyphosis,
chest injuries, chest muscle weakness, chronic lung disease and overuse of sedative drugs.
Metabolic acidosis develops when too much acid is produced in the body. It can also occur
when the kidneys cannot remove enough acid from the body. There are several types of
metabolic acidosis:
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Diabetic acidosis develops when substances called ketone bodies (which are acidic) build up
during uncontrolled diabetes.
Hyperchloremic acidosis is caused by the loss of too much sodium bicarbonate from the body, which can
happen with severe diarrhea.
Lactic acidosis is a buildup of lactic acid. Different types of acidosis can be caused by cancer, renal
failure, and drinking too much alcohol, exercising vigorously for a very long time, liver failure, low blood
sugar (hypoglycemia), medications, such as salicylates, prolonged lack of oxygen from shock, heart
failure, or severe anemia and seizures.
Alkalosis is a condition in which the body fluids have excess base (alkali).
Decreased carbon dioxide (an acid) or increased bicarbonate (a base) level makes the body too
alkaline, a condition called alkalosis. There are different types of alkalosis.
Respiratory alkalosis is caused by a low carbon dioxide levels in the blood. This can be due to
fever, being at a high altitude, lack of oxygen, liver disease, lung disease, which causes you to
breathe faster (hyperventilate) and salicylate poisoning.
Metabolic alkalosis is caused by too much bicarbonate in the blood. It can also occur due to
certain kidney diseases.
Hypochloremic alkalosis is caused by an extreme lack or loss of chloride, such as from
prolonged vomiting.
Hypokalemic alkalosis is caused by the kidneys' response to an extreme lack or loss of
potassium. This can occur from taking certain water pills (diuretics).
One of the most crucial homeostatic mechanisms inside our body is the regulation of the acidbase balance. Recall that the homeostasis is the relative constancy of the internal environment.
Any variation of the pH of blood and body fluids will have a major impact on the activity of the
enzymes, proteins, cell shape and regulation, overall metabolism and normal functioning of the
cells and the body as a whole.
Inside our body to avoid having the pathological states described above (acidosis and alkalosis),
we have buffers that resists any pH changes. They are classified in two categories:
The physiological buffer is either the urinary or the respiratory systems that acts in stabilizing
our body pH by controlling the quantity of acids, bases or CO2 we release.
The chemical buffers are substances that have the ability to bind to any excess of hydrogen ion
available in our body or release it into the fluids once its concentration fails. Because we have
several substances acting as chemical buffers and functioning together, we refer to them as the
“buffer system” and they include phosphate, proteins and bicarbonate.
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In the lab experiment you will be performing, you will explore the principles of acids and bases
by using digital pH meter to accurately determine the pH of a solution and you will also test the
ability of the 2 different buffers (phosphate and albumin solutions) to stabilize the pH.
Phosphate ions are part of the chemical buffer system in our bodies and albumin is a protein
that can also provide buffering capability.
References:
Encyclopædia Britannica Online
http://www.britannica.com/EBchecked/topic/83655/buffer (accessed 06/30/2014)
Encyclopædia Britannica Online
http://www.britannica.com/EBchecked/topic/454823/pH (accessed 06/30/2014)
Brent Wisse, MD, Acidosis
http://www.nlm.nih.gov/medlineplus/ency/article/001181.htm (accessed on 06/30/14)
Brent Wisse, MD, Alkalosis
http://www.nlm.nih.gov/medlineplus/ency/article/001183.htm (accessed on 06/30/14)
pH Wikipedia
http://en.wikipedia.org/wiki/PH_scale (accessed 06/30/2014).
PRE-LAB EXERCISE 1: Adding an Acid to Buffered Solutions
In this exercise:



You will test the ability of water and buffer solutions to stabilize the pH of a solution.
You will be using 3 flasks containing each 3 different solutions: water, albumin solution,
and phosphate solution. Pure water’s pH is 7. Albumin and phosphate solutions have
both a pH value ranging between 7.00 and 7.20.
You will be adding drops of 0.1 molar hydrochloric acid (HCI) to see its impact on the
variation of the pH for each of the 3 solutions.
Pre-Lab 1 Questions:
1. Using what you know about buffers and water, predict how each solution will perform
as a buffer.
2. Rewrite your answer to question 1 in the form of an If … Then … hypothesis.
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PRE-LAB EXERCISE 2: Adding a Base to Buffered Solutions
In this exercise:



You will test the ability of water and buffer solutions to stabilize the pH of a
solution.
You will be using 3 flasks containing each 3 different solutions: pure water,
albumin solution, and phosphate solution. Pure water’s pH is 7. Albumin and
phosphate solutions have both a pH value ranging between 7.00 and 7.20.
You will be adding drops of the sodium hydroxide (NaOH) to see its impact on
the variation of the pH for each of the 3 solutions.
Pre-Lab 2 Questions:
1. Using what you know about buffers and water, predict how each solution will perform
as a buffer.
2. Rewrite your answer to question 1 in the form of an If … Then … hypothesis.
EQUIPMENT:



Paper
Pencil/pen
Computer with Internet access (for the remote laboratory and for data analysis)
PREPARING FOR THIS NANSLO LAB ACTIVITY:
Read and understand the information below before you proceed with the lab!
Scheduling an Appointment Using the NANSLO Scheduling System
Your instructor has reserved a block of time through the NANSLO Scheduling System for you to
complete this activity. For more information on how to set up a time to access this NANSLO lab
activity, see www.wiche.edu/nanslo/scheduling-software.
Students Accessing a NANSLO Lab Activity for the First Time
For those accessing a NANSLO laboratory for the first time, you may need to install software on
your computer to access the NANSLO lab activity. Use this link for detailed instructions on
steps to complete prior to accessing your assigned NANSLO lab activity –
www.wiche.edu/nanslo/lab-tutorials.
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Video Tutorial for RWSL: A short video demonstrating how to use the Remote Web-based Science Lab
(RWSL) control panel for the titration apparatus can be viewed at http://www.wiche.edu/nanslo/labtutorials#titration .
NOTE: Disregard the conference number in this video tutorial.
AS SOON AS YOU CONNECT TO THE RWSL CONTROL PANEL: Click on the yellow button at the
bottom of the screen (you may need to scroll down to see it). Follow the directions on the pop
up window to join the voice conference and talk to your group and the Lab Technician.
EXPERIMENTAL PROCEDURE:
Read and understand these instructions BEFORE starting the actual lab procedure and collecting
data. Once you have logged on to the remote lab system, you will perform the following laboratory
procedures.
EXERCISE 1: Adding an Acid to Buffered Solutions
DATA COLLECTION:
1. In the flask containing water: Using the digital pH meter, measure the initial pH and
record your data in a table.
2. Add 1 drop of the hydrochloric acid (HCI) solution and measure the new pH of the
solution. Record your data in a table.
3. Repeat step 2 nine additional times.
Rinse the pH meter probe.
4. In the flask containing albumin solution: Using the digital pH meter, measure the initial
pH and record your data in table 2 below.
5. Add 1 drop of the hydrochloric acid (HCL) solution and measure the new pH of the
solution. Record your data in a table.
6. Repeat step 5 nine additional times.
Rinse the pH meter probe.
7. In the flask containing phosphate buffer solution: Using the digital pH meter, measure
the initial pH and record your data in Table 3 below.
8. Add 1 drop of the hydrochloric acid (HCL) solution and measure the new pH of the
solution. Record your data in a table.
9. Repeat step 8 nine additional times.
Rinse the pH meter probe.
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ANALYSIS:
10. Compare the final pH of each solution. Which one has “absorbed” the HCI most
efficiently?
11. Which solution is the most effective buffer?
12. Which solution is the least effective buffer?
13. Rewrite your hypothesis in light of your new information collected in this exercise.
14. Graph the variation of the pH vs the drops of HCI and estimate the point at which buffer
stabilization fails.
EXERCISE 2: Adding a Base to Buffered Solutions
DATA COLLECTION:
1. In the flask containing water: Using the digital pH meter, measure the initial pH and
record your data in a table.
2. Add 1 drop of the sodium hydroxide (NaOH) solution and measure the new pH of the
solution. Record your data in a table.
3. Repeat step 2 nine additional times.
Rinse the pH meter probe.
4. In the flask containing albumin solution: Using the digital pH meter, measure the initial
pH and record your data in a table.
5. Add 1 drop of the sodium hydroxide (NaOH) solution and measure the new pH of the
solution. Record your data in table 5 below.
6. Repeat step 5 nine additional times.
Rinse the pH meter probe.
7. In the flask containing phosphate buffer solution: Using the digital pH meter, measure
the initial pH and record your data in a table 6 below.
8. Add 1 drop of the sodium hydroxide (NaOH) solution and measure the new pH of the
solution. Record your data in a table.
9. Repeat step 8 nine additional times.
Rinse the pH meter probe.
ANALYSIS:
10. Compare the final pH of each solution. Which one has “absorbed” the NaOH most
effectively?
11. Which solution is the most effective buffer?
12. Which solution is the least effective buffer?
13. Rewrite your hypothesis in light of your new information collected in this exercise.
14. Graph the variation of the pH versus the drops of NaOH and estimate the point at which
buffer stabilization fails.
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SUMMARY QUESTIONS
1. Based on the experiment you just completed above, how do you explain the difference
in the buffering capacities between the solutions you tested?
2. Based on your understanding of the pH scale, calculate the hydrogen ion concentration
of a solution:
a. with a pH 7.0?
b. with a pH 9.0
c. with a pH of 4.0?
3. The pH of blood in the human body is between 7.35 and 7.45. Discuss the benefits of
healthy eating and exercises in maintaining homeostasis.
4. You are working in an independent laboratory and you want to investigate the
effectiveness of different commercial antacids such as Tums, Maalox, Alka-Seltzer in
neutralizing the hydrochloric acid produced by the stomach. How will you conduct your
investigation?
5. Explain the role of the respiratory system in maintaining normal blood pH?
6. Research the buffering activity of hemoglobin. Describe what you find to the best of
your ability.
For more information about NANSLO, visit www.wiche.edu/nanslo.
All material produced subject to:
Creative Commons Attribution 3.0 United States License 3
This product was funded by a grant awarded by the U.S.
Department of Labor’s Employment and Training Administration.
The product was created by the grantee and does not necessarily
reflect the official position of the U.S. Department of Labor. The
Department of Labor makes no guarantees, warranties, or
assurances of any kind, express or implied, with respect to such
information, including any information on linked sites and
including, but not limited to, accuracy of the information or its
completeness, timeliness, usefulness, adequacy, continued
availability, or ownership.
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