Vinegar Titration Lab

Research Questions:

  1. How do we work within the limitations of this measurement tool in order to produce an accurate and precise experimental measurement?

  2. What is the acetic acid concentration of commercial vinegar?

Learning Objectives:

  1. Use surface tension based micro paper analytical devices to make accurate measurements of vinegar concentrations

  2. Use a color reading app to correctly detect experimental endpoint

  3. Use acid-base concepts to predict and test endpoint pH

  4. Use stoichiometry concepts to measure the acetic acid concentration of vinegar

  5. Use scientific data to develop experimental procedures

  6. Determine sources of experimental failure and iterate on experimental procedure

  7. Evaluate the significance of experimental data using appropriate statistics

To Do List:

Step 1: Read lab background, watch videos, and visit links provided about experimental context on this page

Step 2: Read lab procedure

Step 3: Watch corresponding lab tutorials

Step 4: Answer pre-lab questions

Step 5: Perform lab experiment

Step 6: Answer post-lab questions

Acid Rain Pathway. This image illustrates the pathway for acid rain in our environment. Emissions of sulfate and nitrate are released into the air, where the pollutants are transformed into acid particles that may be transported long distances. These acid particles then fall to the earth as wet or dry deposition (dust, rain, snow, etc.) and may cause harmful effects on soil, forests, streams, and lakes.

Acid Rain and Acid Mine Drainage

Acid rain and acid mine drainage, both consequences of coal mining and production, can cause severe illness in humans and aquatic life. Acid rain can be caused by coal production and emissions from that process. Acid rain can endanger wildlife species that live in and drink the water that is made up of this rain. Acid mining is caused by abandoned mines that drain toxic chemicals into nearby water sources.

Acid rain is defined as atmospheric precipitation with a pH below 5.2, however it generally has a pH between 4.4 and 4.2.1 Clean rainwater has an average pH of 5.6 which is slightly acidic due to the dissolution of carbon dioxide and formation of a dilute carbonic acid.1 Acid rain can be caused by both man-made and natural sources. Emissions resulting from fossil fuel combustion are the primary cause of acid rain, as they release sulfur dioxide and nitrogen oxides into the atmosphere.1 From these gases, sulfuric acid and nitric acid can form and dissolve into the water vapor in the atmosphere.

Acid Rain

In most cases, the environment can adapt to certain levels of acid rain. Soil is generally basic due to naturally occurring limestone deposits, which helps to balance out the acidity of the rain before it is able to cause damage to the surrounding environment.2 Essentially, the limestone creates a buffer which prevents the levels of acid from becoming hazardous. In areas where the soil does not naturally contain limestone, or there isn’t soil in the area to buffer the rain, many plants and animals are unable to adapt to the change in pH and will ultimately be harmed.2 Generally, freshwater aquatic life are the first to be affected by environmental acidification, however this goes on to affect the rest of the food chain.

The health hazards of acid rain for humans are not direct; swimming in an acidic body of water is no more harmful than swimming in a clean body of water.3 However, areas with high accounts of acid rain have been linked to increased respiratory conditions such as pneumonia, asthma, and bronchitis, as well as various heart disorders.3 These diseases are especially dangerous to those populations with preexisting conditions or inadequate accessibility to health care. African Americans are affected by asthma at a 36% higher rate than white americans, are hospitalized for asthma at three times the rate of white Americans, and have a mortality rate twice that of white Americans in relationship to asthma.4

Critical pH levels for aquatic organisms. This figure illustrates the pH level at which key organisms may be lost as their environment becomes more acidic. Not all fish, shellfish, or the insects that they eat can tolerate the same amount of acid. The highest critical pH level being that of a snail which is 6, and the lowest critical pH level of a frog at 4.
This image is the hydrogen ion concentration as pH from measurements made at the Central Analytical Laboratory, 2005. Midwestern and Western America has a higher pH of 5.1 and above. Eastern US has much lower pH values of 4.6 and lower.

Although these hazardous emissions originate in urban or industrial areas, and mainly affect the surrounding areas, the acidic vapors can be carried by wind hundreds of miles to rural areas as well.1 Historically, the north eastern United States has been an area of great concern due to the migration of vapors from midwestern coal-burning factories.5 The level of emissions in the United States has greatly decreased as a result of the Clean Air Act of 1970.5 Amendments made to the act in 1990 significantly limit the acceptable amount of both sulfur dioxide and nitrogen oxides from industrial plants, and have prevented the dangerous effects of air pollution.5 Unfortunately there are still many areas of the northeast United States that have not environmentally recovered from the previous lack of regulation, and continue to suffer from the results of the acidification of freshwater sources.5 78% of African Americans live within 30 miles of a coal-fired power plant, as opposed to 56% of white Americans.4 Additionally, there are areas which consistently violate air pollution standards; 71% of African Americans live in counties violating federal regulations as compared to 58% of the white population.4

Currently, areas with rapid industrialization and few pollution regulations, like India and China, are at the greatest risk for suffering the harmful effects of acid rain.7 Developing nations, with increasing demand for electricity and manufactured goods, may reach crisis pollution levels, similar to those of the United States in the 1980s, if they do not implement emission regulations.5 The technologies needed to study acid rain in developing nations with increasing urbanization are often unavailable, expensive, or inadequate.7 The primary method for detection of acid rain is the collection of rainwater samples and analysis of the sample’s pH. Acid-base titrations in the lab are very important to understanding the delicate balance of pH, especially in the environment. A successful microfluidic titration can be used to calculate the amount of acid present in the sample. This method could theoretically be used to determine the acidity of a rain water sample indicating the possibility of environmental hazards.

Acid Mine Drainage

This image depicts a stream polluted by acid mine drainage. The water is an orange-yellow color.

Acid mining drainage occurs when mining for materials like metals includes polluted water draining from the mining site. Before there were strict rules on what chemicals can be used for mining, harmful contaminants were left in the mines and water that would drain from them. When regulations became active and enforced, the old mines were abandoned and the harmful materials were left to pollute nearby freshwater. This drainage is highly acidic and damages environments and biosystems around the drainage sites. The water can also contain highly toxic materials that can be very harmful for human consumption.8 The low, acidic pH of this mining draining releases toxic metals into the water which can harm the wildlife, vegetation, and humans consuming the water. This acidification of the water can last long after the mining is complete in the area.9 High acidity in animals can cause acidosis which can have very bad health effects.

This figure depicts different abandoned coal mines across the country. There is a large band of abandoned mines from North Dakota all the way down to Mexico. There is another clump of mines in Indiana and Kentucky. Another band of mines can be found that stretches form Pennsylvania toTennessee.

This mining is often coal mining, which is most frequently found in impoverished areas. According to the newest census, the poverty rates in coal mining communities are much higher than the national average.11 The damaging consequences of acid mining drainage often harm more people of color than non-hispanic white Americans.

Currently, there are some plans to move pathways of natural water away from the polluted acid mine drainage water. If these waters mix, there would be a much larger volume of polluted waters. The plans to try and minimize the amount of polluted water include:

  1. Diversion of surface water flowing towards the site of pollution

  2. Prevention of groundwater infiltration into the pollution site

  3. Prevention of hydrological water seepage into the affected areas

  1. Controlled placement of acid-generating waste8

Laboratory Context

It is important for chemists to be able to identify the subtle pH changes in water sources, especially acid mining drainage and acid rain sites. Determining where water is too acidic can be done through simple titrations. In this lab, we will use a microfluidic device to determine the acid content of an aqueous solution, specifically acetic acid in vinegar. The changes in pH throughout the sample will be visible by color change on the pH paper.

To perform a titration on microfluidic devices, vinegar (which is acidic) must be added to the devices. Basic NaOH is already deposited on the devices in different concentrations so adding the vinegar to the chip will create a titration. The chips will turn color based on the pH due to the pH paper on the chip. The point of equivalence will be visually detectable. This concept could be used when testing acid mining drainage to determine the acidity of the contaminated water. The vinegar would act like the acid polluted water and the titration will show the concentration of acid found in the water.

Read about Dr. Nancy Allbritton, Dean of the University of Washington College of Engineering, Professor of Bioengineering, and Major Contributor to the field of Analytical Chemistry

Learn More!

Solutions for reducing acid rain affects: Reducing Acid Rain Or Its Effects | Environmental Chemistry | Chemistry | FuseSchool

Here is an in depth chemical explanation, visit Acid rain | Environmental Chemistry | Chemistry | FuseSchool.

To learn more about the elevate rates of asthma in black communities, visit Health Disparities, Focus on Asthma | Children's National Medical Center.

Find out more about the effects of acid rain on the human body here: What Does Acid Rain Do To Your Body.

A community example of acid mining drainage can be found here Acid mine drainage.

A complete map of abandoned coal mines in America could be found at SkyTruth – US Abandoned Coal Mines (eAMLIS Database).

To find out more about solutions to acid mining drainage, visit What can be done to prevent or clean up acid mine drainage?

References

  1. “What Is Acid Rain?” EPA, Environmental Protection Agency, 12 May 2020, www.epa.gov/acidrain/what-acid-rain.
  2. “Acid Rain and Water.” USGS Science for a Changing World, U.S. Department of the Interior , www.usgs.gov/special-topic/water-science-school/science/acid-rain-and-water?qt-science_center_objects=0#qt-science_center_objects.
  3. “Effects of Acid Rain - Human Health.” The Environmental Protection Agency Napa County, California, Trilogy Integrated Resources , napa.networkofcare.org/ph/library/article.aspx?id=1736.
  4. “ENVIRONMENTAL JUSTICE.” Citizens Coal Council, Citizens Coal Council , www.citizenscoalcouncil.org/environmental-justice.html.
  5. Echolls, Taylor. “What Place in the World Receives the Most Acid Rain?” Sciencing, 2 Mar. 2019, sciencing.com/place-world-receives-acid-rain-23289.html.
  6. Lewicke, A.; Finkelstein, N.; Griswold, A.; Schneps, M.; Cane, M. The habitable planet; [Annenberg Media]: [S. Burlington, Vt.], 2007.
  7. Rastogi, Archi. “Industrialisation Bringing Acid Rain to India.” Down To Earth, Down To Earth, 5 July 2015, www.downtoearth.org.in/news/industrialisation-bringing-acid-rain-to-india-6625.
  8. Akcil, A.; Koldas, S. Acid Mine Drainage (AMD): Causes, Treatment and Case Studies. J. Clean. Prod. 2006, 14 (12–13), 1139–1145. https://doi.org/10.1016/j.jclepro.2004.09.006.
  9. Kumari, S.; Udayabhanu, G.; Prasad, B. Studies on Environmental Impact of Acid Mine Drain. Indian J. Environ. Prot. 2010, 30.
  10. Mine Drainage. https://www.usgs.gov/mission-areas/water-resources/science/mine-drainage?qt-science_center_objects=0#qt-science_center_objects (accessed Jul 2, 2020).
  11. Environmental Justice http://www.citizenscoalcouncil.org/environmental-justice.html (accessed Jun 22, 2020).