Question

What is phenolphthalein alkalinity? How is it related to the hydroxide and carbonate levels in water?

Answer 1

Let us know that alkalinity is a feature of water that is reliant on the presence of certain compounds in the water, such as bicarbonates, carbonates, and hydroxides. "The buffering capacity of a water body; a measure of the water body's ability to neutralize acids and bases and so maintain a fairly steady ${\text{pH}}$ level," would be a definition of alkalinity. Water with high alkalinity will change its acidity less than water with low alkalinity.

Complete answer:
We know that the capacity of water to neutralize acids is measured by alkalinity. The presence of carbonate, hydrogen carbonate and hydroxide ions in water causes alkalinity.
Phenolphthalein alkalinity is a specific category of alkalinity. At ${\text{pH 8}}{\text{.3}}$, phenolphthalein alkalinity measures the hydroxides and half of the carbonates.
Titration of the sample to an end point of ${\text{pH 8}}{\text{.3}}$, which corresponds to the end point of the phenolphthalein indicator, is used to determine phenolphthalein alkalinity. Total alkalinity is divided into phenolphthalein alkalinity and phenolphthalein alkalinity. The phenolphthalein method can be used to measure individual amounts of hydroxide, carbonate, and bicarbonate. This is how phenolphthalein alkalinity is related to the hydroxide and carbonate level in water.

NOTE:
It can be noted that at a ${\text{pH}}$ of ${\text{4}}{\text{.5}}$, total alkalinity is defined as the sum of all carbonate, bicarbonate, and hydroxide alkalinity (approximately). The total alkalinity of a sample is determined by titrating it to a ${\text{pH}}$of ${\text{4}}{\text{.5}}$, which corresponds to the end point of the bromocresol green-methyl red indicator. In other words, total alkalinity refers to the concentration of all alkaline compounds dissolved in water that can accept and release hydrogen ions.