Something that can identify the acidity and alkalinity of a solution

In modern society, people pay more and more attention to the acidity and alkalinity of things around them. The acidity and alkalinity of things affect our health. Different solutions have different acidity and alkalinity. If the acidity and alkalinity ratio is too high, it will lead to poisoning. There are many ways to measure the acidity and alkalinity of solutions. Most people use pH test paper, but not everyone has this kind of thing at home. This is a kind of chemical test paper. So what is the thing that can identify the acidity and alkalinity of a solution?

An acid is a compound in which all cations produced upon ionization are hydrogen ions ; a base is a compound in which all anions produced upon ionization are hydroxide ions; a salt is a compound in which all metal cations (or ammonium ions) and acid ions are produced upon ionization. It can be simply recorded as: hydrogen-based acids, hydroxide-ending bases, and metal-based acids ending in salts. Acids, alkalis and salts are important knowledge points in chemistry learning.

Acids are substances in which all the cations produced when ionized are hydrogen ions;

Alkali are a class of substances that, when ionized, produce only hydroxide ions as anions.

According to their definitions, we can distinguish them: hydrogen ions can turn purple litmus red, while hydroxide ions can turn purple litmus blue, so the way to distinguish them is to add drops of purple litmus.

Hydrogen ions cannot change the color of colorless phenolphthalein, but hydroxide ions can turn colorless phenolphthalein red, so adding colorless phenolphthalein can also distinguish it.

Note: Acid can change the color of the indicator, but it is not necessarily acid that can change the color of the indicator, it may be an acidic solution. The same is true for alkali.

If judging by chemical formula, then we need to pay attention to two points: 1. Whether the chemical formula contains hydroxide (or hydrogen ion).

2. Are all cations in the formula hydrogen ions (or all anions hydroxide ions)?

For example: NaHCO3 sodium bicarbonate is not an acid, because although it has hydrogen ions, its cations are not all hydrogen ions, it also contains sodium ions, so it is not an acid. Another example: Cu2CO3 (OH) 2 alkaline copper carbonate, it is not an alkali either, because although it has hydroxide, its anions are not all hydroxide, it also contains carbonate, so it is not an alkali.