Difference Between Acidity And Alkalinity Of Water

Water is a vital component of life, and its pH level can enormously impact our health. The acidity or alkalinity of water is determined by the number of hydrogen ions (H+) in the water. Acidity refers to a solution with a low pH below 7.0; alkalinity is defined by a high pH above 7.0. The higher the number, the more base (alkaline) the solution. Anything between 6.5 and 8.5 is considered to be neutral.

What Is The Acidity Of Water?

The acidity of water is a measure of how acidic or basic the water is. The pH scale ranges from 0 to 14, with seven being neutral. A reading below 7 indicates that the water is acidic. Acidity is measured in terms of hydrogen ion concentration (pH). When the pH level is lower than 7, the water is considered acidic and has a higher hydrogen ion concentration.

What Is The Alkalinity Of Water?

Alkalinity is a measure of the water’s ability to neutralize acids. pH level above 7 indicates water is alkaline. It is usually measured in terms of calcium carbonate equivalent (CaCO3 eq./L). The higher the alkalinity, the more resistant it is to changes in pH caused by adding acid or base. Alkalinity helps buffer pH changes, preventing drastic shifts that could harm aquatic life. Higher alkalinity also means higher water hardness, as minerals such as calcium and magnesium contribute to the alkalinity of the water.

Difference Between Acidity And Alkalinity Of Water

  • Components: Water’s acidity is water’s ability to neutralize a base. On the other hand, water’s alkalinity is water’s ability to neutralize a base.
  • Determination: The acidity of water is determined via titration with a standard base such as sodium hydroxide. The alkalinity of water can be determined via titration with a standard acid such as hydrochloric acid.
  • Water quality: The acidity is higher in polluted water. At the same time, clean water has alkalinity rather than acidity.
  • Sources: The acidity of water is caused by the presence of carbon dioxide, hydrogen sulfide, and sulfuric acid. The alkalinity of water is due to the presence of salts and minerals like calcium, magnesium, bicarbonate, carbonate, and hydroxide ions.
  • Effects: The pH of water can be affected by acidity and alkalinity. High levels of acidity lead to decreased oxygen levels in the water, making it toxic for aquatic life. At the same time, high levels of alkalinity make the water more hospitable for aquatic life.

How Can An Acidic Solution Become Completely Alkaline?

  • Alkalinity is increased by adding baking soda or potassium carbonate to water.
  • ¬†Adding sodium bicarbonate (baking soda) to acidic water will increase its pH level and render it alkaline. It is important to note that this method can only be used for minor changes in pH as it does not raise the alkalinity of the solution by much.
  • Another method of increasing alkalinity is to add lime, or calcium hydroxide, to the solution. This will increase the alkalinity and raise the pH levels significantly.
  • Another option for increasing alkalinity is to use caustic soda, also known as sodium hydroxide, in the solution. Caustic soda is a stronger alkali and will have a much more significant effect on pH levels than baking soda.
  • Potassium carbonate, or potassium bicarbonate, is another option that can be used to raise the alkalinity of a solution. This method also has a dramatic effect on pH levels.

Acidic solutions can be neutralized and rendered entirely alkaline using these methods. It is important to note that if the pH level needs to be raised drastically, such as from a pH of 4.5-5.0 to 7.0, it is more effective to use caustic soda or potassium carbonate. Baking soda is only effective for minor changes, and lime should be used cautiously as it can increase the water’s hardness.

How Does Acid Neutralize The Effect Of Alkaline?

To neutralize the effect of one on the other, an acid has to donate its hydrogen ions, while an alkaline substance must donate its hydroxide ions. This creates a balanced solution with a pH of 7. This process is crucial because it helps maintain a balanced pH in water, which is essential for sustaining life. For example, fish and other aquatic organisms can only survive in environments with a balanced pH.


Why acidity and alkalinity are expressed in terms of caco3?

The acidity and alkalinity of water are expressed in terms of caco3 because the concentration of carbon dioxide ions affects its pH level. Carbon dioxide (CO2) is a weak acid, so it tends to dissociate into hydrogen ions (H+) when dissolved in water.

Which ions will cause the alkalinity of water?

This can depend on the water source, but it is typically composed of bicarbonates (HCO3-), carbonates (CO32-), and hydroxides (OH-). Bicarbonates are the most common alkaline ion in natural water sources.

What is the significance of alkalinity?

Alkalinity measures a water’s ability to neutralize acid and resist changes in pH. A highly alkaline environment can protect aquatic life, as it acts as a buffer against sudden changes in pH caused by sources such as runoff and other pollutants.

What water samples have both alkalinity and acidity?

Water samples with both alkalinity and acidity are known as neutral water. Neutral water has a pH of around 7, which is neither acidic nor alkaline. Such samples can be found in natural bodies of water such as rivers and lakes and some artificial sources.


water can be acidic or alkaline, depending on the concentration of hydrogen ions in it. Acidity is measured using the pH scale and ranges from 0 to 14. Water with a pH lower than 7 is said to be acidic, while water with a pH higher than seven is alkaline. Understanding the difference between acidity and alkalinity of water is important as this can significantly impact aquatic ecosystems, human health, and other organisms. Therefore, it is important to monitor the pH levels of water sources to ensure they remain within an acceptable range for their respective environment.

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