How to tell if an acid is strong or weak

1.Determination of the amount of concentration of a known substance and the pH of a weak acidIf the acid Hb is known, the concentration of the substance is, if it is a strong acid, it is completely ionized, pH = 2; If it is a weak acid, the pH > 2

2.Take a certain volume of acid Hb solution (set to take a volume), measure its pH, dilute it to a 10-fold increase in pH, and then measure its pHIf the pH increases by one unit, it is a strong acid; If the pH increases by less than one unit, it is a weak acid.

3.Take the sodium salt solution corresponding to acid Hb and determine its pHIf pH=7, it is a strong acid; If the pH > 7, it is a weak acid. (This method works!) )

4.Take the same volume and pH of acid HB solution and hydrochloric acid, respectively, add a sufficient amount of zinc grains, if HB produces hydrogen at a large rate and a large amount, it means that it is a weak acid.

5.If the volume of sodium hydroxide solution of the same concentration consumed by acid Hb at the end point is large, Hb is a weak acid.

6.The amount and concentration of acid HB solution and hydrochloric acid of the same substance were taken respectively to measure their conductivity, if the conductivity of acid HB solution is weak, it means that HB is a weak acid.

I just think of it for the time being, and the third one is the best. Others are also a way to go. Theoretically guaranteed to work! Hopefully it is. Have a chemistry question to ask me.

First of all, there is no specific standard for strong and weak acids, which are relative.

You can get an idea with a pH test strip.

With known acids, example; Hydrochloric acid. After adding water to the two acids, the degree of ionization is measured, and the high degree of ionization is a strong acid, and vice versa.

Metallic iron is put into hydrochloric acid and unknown acid respectively, and whether there are bubbles, which is a strong acid, and vice versa.

Generally speaking, there are several kinds of strong acids, sulfuric acid, hydrochloric acid, etc., and some compounds with metal ions, such as compounds with barium ions, can identify sulfuric acid.

There are many methods, such as the knowledge of ionization equilibrium, the method of identifying its acid roots, and many physical methods, such as whether there is a color, whether there is a smell, etc.

Sulfuric acid, hydrochloric acid, nitric acid, trianchoic acid.

Generally, most of them are weak acids, especially those with a valency of less than -1.

Strong acids are strong electrolytes. In the aqueous solution, it is completely ionized (all the H contained in it is ionized to produce H+), a weak acid, that is, a weak electrolyte. In aqueous solutions, partially ionized (contains h and only partially ionized) solutions also contain electrolyte molecules.

With a pH meter, if the pH of A is lower than B at the same concentration, A is a weak acid.

There are only backrests, and there are only those types used in the exam, so it is easy to distinguish.

1. The definition of acid-base is:

1. Any substance that can release protons, whether it is a molecule, an atom or an ion, is an acid.

2. Any substance that can accept protons, whether it is a molecule, atom or ion, is a base.

Second, the method of distinguishing strong acids and weak acids depends on the concentration of hydrogen ions. Strong acids are completely ionized in aqueous solution, which is the biggest difference between moderately strong acids and weak acids.

3. The difference between strong acid and weak acid with the same pH: pH value refers to the concentration of hydrogen ions that have been ionizedStrong acid is completely ionized, and weak acid is partially ionized, so the amount and concentration of weak acid substances with the same volume and pH value is much greater than that of strong acid, and the concentration of hydrogen ions in weak acid in alkali reaction decreases, so the equilibrium moves in the direction of hydrogen ion increase.

01 First of all, we should be clear about a knowledge point, what belongs to strong acids and what belongs to weak acids. Acids that can completely ionize hydrogen ions in solution are called strong acids, and acids that can be completely ionized by hydrogen ions in solution are called weak acids.

02 Of course, whether hydrogen ions can be completely ionized can be judged by the ionization constant (ka), generally speaking, PKA (acidity coefficient, negative logarithm of ionization constant) less than 1 is a strong acid (note: pka=1 4 is a medium strong acid, more than 4 is a weak acid. ）

03 In practical use, we are generally familiar with some common strong acids and weak acids, and we can basically deal with common chemistry test questions. For example, some common inorganic strong acids: sulfuric acid (H2SO4), nitric acid (HNO3), perchloric acid (HCl4), hydrochloric acid (HCl), hydrobromic acid (HBR), hydroiodic acid (HI), perbromate acid (HBRO4), chloric acid (HCO3), bromine acid (HBRO3), fluorosilicic acid (H2SIF6), chlorine lead acid (H2PBCl6), metaphosphoric acid (HPO3), permangantic acid (HMNO4), cyanic acid (HOCN), thiocyanic acid (HSCN), Periodic acid (HIO4), etc.

Some common weak acids: carbonic acid (HCO), acetic acid (CH3COOH), hypochlorous acid (HCl), hydrofluoric acid (HF), sulfurous acid (H2SO3), etc.

04 Of course, we can also use experimental methods to distinguish between using a pH meter to measure acidic aqueous solutions with the same concentration, the lower the pH value, the more acidic it is.

1. Prepare the solution, measure the pH, and the one greater than the complete ionization is a weak acid;

2. Take the positive salt of sodium, dissolve it in water to measure pH, and the one greater than 7 is weak acid;

3. Prepare a solution with pH 1, dilute 10 times, measure pH, if less than 2 is weak acid.

HCO4 perchloric acid, hydroiodic acid, hi nitroic acid (nitric acid), HNO3, hydrobromic acid, HBR, hydrochloric acid (hydrochloric acid), HCl, H2SO4 sulfate

Except for these six, they are all moderately strong acids or weak acids. 】