In the Indicator sponge experiment, the main purpose of the experiment is to create an acid-base indicator with a sponge. An indicator works as a color dye that is a large organic molecule. The molecules change color by responding to the change in hydrogen ion concentration. Acid Base indicators are also known as pH indicators because they change colors with pH. The acids usually used in indicators are usually weak or bases. The base/weak acid is dissociated in water to create ions to be used to indicate pH. The indicator uses the following equilibrium equation with the formula HIn:
HIn (aq) + H2O (1) = H3O+ (aq) + In- (aq)
(Acid [color A]) (Conjugate base [color B])
As shown in the equation: to the left is the acid that will indicate its properties with the change to the color blue and to the right is the base that will change to the color of red with the indicator.
Indicators aren't always red and blue, for example, Phenolphthalein as an acid it is colorless and as a base it is the color of pink.
The Congo Red solution added into the sponge allows the sponge to change color based on the pH level within the solutions of HCL and NaOH. The Congo red indicator strip goes from pH range 3.o(Blue) to 5.0(red). HCL is in the color of red along the pH strip and NaOH is the color blue along the pH strip.
Acid-base is also associated with homeostasis of the body fluids. The acid-base arterial blood pH level should normally range between 7.37 to 7.43. Acids are usually proton donors within the body while the base (AKA Alkali) combines with protons to create a chemical bond. They vary greatly as acids are painful to touch and can burn while a base is usually slippery and smooth. Acids are important to human health as hydrochloric acid is secreted from the stomach to help digestion while the food eaten that goes through the stomach contain protein, chloride, phosphorus, sodium, potassium, calcium and magnesium that are used as bases to the secreted acid of the stomach. Another part of the body that contains an acid-base balance are body fluids and cells that contain acid-base buffers. They rapid changes in body fluid pH by having the kidneys and pulmonary system balance it out by excreting urine and respiration(carbon dioxide). Failures in acid-base balance are resulted from metabolic or respiratory failures. Whether it be an increase in HCO3 or PCO2, they are all a form of a condition called alkalosis. If it is a decrease in HCO3 or PCO2, it is a condition called acidosis. Acidosis is a condition that isn't much of a disease but can indicated diseases caused by the increase in acid levels. Alkalosis is when there is excessive alkalinity in blood and body tissue which can cause nerve and muscle problems, sometimes even death.
In the indicator sponge experiment, there are certain chemicals used to represent the acid and the base.
-Hydrochloric Acid (HCI): It is used in the production of fertilizers, dyes and chlorides as well as being use in rubber industries and textiles. Since it is an acid, it is highly corrosive to the eye, skin, and mucous membrane. If inhaled acutely, it can cause eye, nose, and respiratory irritation and inflammation. If orally consumed, it can cause ulceration and scaring of the human body (esophagus, stomach, etc). It is colorless and non flammable. Its molecular weight is 36.47 g/mol. It however has a repugnant smell.
-Sodium Hydroxide (NaOH): is odorless and is a white solid. It absorbs moisture in the air. It is used in textiles, production in paper, etc. Sodium hydroxide is highly corrosive as well with the same reactions as hydrocloric acid.
Sources:
<http://www.sciencetoolbox.com/articles/article_06-15-04.html>
<http://www.elmhurst.edu/~chm/vchembook/186indicator.html>
<http://www.ch.ic.ac.uk/vchemlib/course/indi/indicator.html>
<http://www.enotes.com/topics/acid-base-balance>