pH Value of Water - seeeeee.pdf

2-Hydrolysis (hydration) A small percentage of water molecules are in the form of hydrogen ions (H+) and hydroxide ions (OH-), and as a result of chemical reactions with various compounds, some salts present in natural waters are hydrolyzed, which affects the balance of these ions, causing the acidi...

2-Hydrolysis (hydration) A small percentage of water molecules are in the form of hydrogen ions (H+) and hydroxide ions (OH-), and as a result of chemical reactions with various compounds, some salts present in natural waters are hydrolyzed, which affects the balance of these ions, causing the acidity or basicity of the water. Practical example When table salt (NaCl) is added to water, it dissociates into sodium ions (Na+) and chloride ions (CI-), and the salt ions remain in the solution without binding to the water ions, making the solution neutral because the concentration of hydrogen ions (H+) equals the concentration of hydroxide ions (OH-). In the case of sodium bicarbonate (NaHCO3), hydrolysis occurs, which leads to a decrease in the concentration of hydrogen ions (H+) and an increase in the concentration of hydroxide ions (OH-), making the salt solution basic. The opposite occurs when ammonium chloride (NH4CI) is dissolved in water, which hydrolyzes, causing a decrease in the concentration of hydroxide ions(OH-) and an increase in the concentration of hydrogen ions(H+), making the salt solution acidic. 3-Acid-base balance -Acid-base balance in water depends on, the relationship between the concentration of hydrogen ions (H+) and hydroxide ions (OH-). -This relationship can be identified through the value of what is called the pH of the solution. -It is a graduated scale that takes values from 0 to 14. If the concentration of H+ increases, the water becomes acidic and the pH value is less than 7, and if the concentration of OH- increases, the water becomes basic and the pH value is greater than 7. While if the concentration of the two ions is equal, the water is neutral and the pH value is equal to 7. The pH : Is a measure of the acidity or basicity of water. Pure water has a pH of about 7, which is considered neutral. However, this number can vary in natural environments, affecting the organisms that live in them.  pH value of water from different sources 1.Seawater: The pH value of seawater generally ranges between 7.5 and 8.4 depending on the area in which the sea is located and the surrounding environmental factors. 2. Fresh water rivers and lakes: have a pH value that varies and usually naturally ranges between 6.5 and 8.5. 3.Distilled water: Has a pH value of about 7, because it is free of most of the impurities and ions that contribute to the acidity or basicity of other natural water sources. 4.Groundwater: The pH of groundwater varies from one area to another depending on several factors, the most important of which is the rock composition of the area. Groundwater is either neutral or basic, and its pH value varies due to exposure to calcium carbonate or magnesium carbonate rocks. 5.The pH of clouds: is generally slightly acidic, with values ranging from 4.5 to 5, due to the presence of carbon dioxide and other acidic gases dissolved in the water droplets. These values can vary depending on different environmental factors, human activities in that area which can affect the pH level when clouds or rainwater are formed.  Strong Acids Weak Acids Perchloric acid HCIO4 Carbonic acid H2CO3 Hydroiodic acid HI Phosphoric acid H3PO4 Hydrochloric acid HCl Acetic acid CH3COOH Formic acid. Hydrobromic acid HBr Citric acid. Sulphuric acid H2SO4 Oxalic acid. Nitric acid ΗΝΟ3 Lactic acid. Strong Base Weak Base Potassium hydroxide KOH Ammonium hydroxide NH4OH Sodium hydroxide NaOH Barium hydroxide Ba(OH)2