In the past two centuries the CO2 concentration has increased in the atmosphere as the result of human activities. High CO2 concentration and its related “carbon problem” has gained increasing attention in the scientific communities. One of the carbon related problems is “ocean acidification”. The oceans serve as a carbon sink and the amount of CO2 absorbed by the ocean increases proportional to the levels of atmospheric CO2. The dissolved CO2 and water combine to form carbonic acid, that its dissociation results indecrease in the pH of ocean's surface. Considering the pH value of the ocean, this change represents about 30% increase in ocean acidity. Herein we describe an indicator-based color change to highlight and visualize the ocean acidification by CO2absorption through the air. This demonstration consists of putting a beaker of “soda water” in a closed container next to the bakers include tap water and distilled water containing acid base indicators. The color change of indicator before and after exposure to different volume of CO2 (Fig 1) indicates the acidification. Using universal indicator allowed to demonstrate how acidic the solutions get upon exposure to high CO2 contents. The use of the phenol red, with pKa around the pH of ocean's surface, enable to track the minimal pH changes. Various CO2 sources including combustion and CO2 tank, and variety of measurement techniques have been utilized to measure the effect of absorbed CO2 into the water.1 However, using soda water as an obvious CO2 source,2 enabled an engaging general chemistry laboratory experiment exploring the equilibration and transferring acidity through the air. Using different indicators revealed also the importance of choosing the right acid-base indicator for accurate validation of pH changes.

Indicator-based visualization of ocean acidification as the result of CO2 dissolution

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.