University:
Texas A&M University
Course:
CHEM 119 | Fundamentals of Chemistry I
Academic year:

2020
Views:

325

Pages:

1
Author:

Dixie Summers

Water’s the Matter-Measuring pH Notes Outline KEY Introduction • • pH stands for the “potential or power of hydrogen” and measures the concentration of hydrogen ions in a solution. pH is also described as “acidity” and is a physical/chemical property of water. Lesson • • • • • • • • • • • • • • • • An ion is an atom of hydrogen that has lost its electron. The pH of water is measured on a scale from 0 to 14, which is a logarithmic scale. This means that an increase or decrease of an integer value changes the concentration by a factor of ten. Approximately 60% of a normal adult is made up of water, which reveals that it is essential for life. Water is made up of hydrogen ions (H+) linked to hydroxyl ions (OH-) to form H2O, which is the molecular formula of water. A mole of a substance contains a particular number of molecules. This number is called Avogadro’s number and is equal to 6.02 x 1023. In water, a few water molecules split and create free H+ and free OHmolecules. In pure water, deionized water, these amounts are equal/different. An acidic solution has a low/high pH, which means that is has a lower/higher concentration of hydrogen ions than a neutral solution. Any solution with a pH more/less than 7.0 is said to be acidic. A basic solution has a low/high pH, which means that is has a lower/higher concentration of hydrogen ions that a neutral solution. Any solution with a pH lower/greater than 7.0 is said to be basic. Neutral solutions have a pH value close to or equal to 7.0. On the pH scale from 0 to 14, 0 is the most acidic and 14 is the most basic. The majority of aquatic organisms prefer a pH range of 6.5-9.0. If pH is not withing this optimal level, the organism may not be able to survive. In general, more acidic/basic conditions tend to cause animals to become less excitable. Acidic and alkaline (basic) compounds can be naturally released into the water from different types of rocks or soil, which can change the pH of the water. Carbon dioxide in water can form a weak acid/base. The formation of sulfuric acid due to water flowing over or through rocks at mine sites can result in lower pH levels. Rain water can combine with airborne pollutants to create nitrous oxides and sulfur dioxides that will make the rain water more acidic/basic.