The phenomenon and causes of sulfuric acid and purple litmus solution, sulfur dioxide into purple li

There is no chemical equation for indicators and acid-base reactions.

The color of all the indicators in the solution is actually the color of the indicator itself, but in different forms, take litmus as an example, litmus itself is red when dissolved in water, and at the same time it will ionize to generate negatively charged ions purple, because litmus is a weak electrolyte, so only a part of it is ionized in water, and there are both red and purple substances in the solution, so the comprehensive color is blue.

The principle of color-changing of acid-base indicators is:

hin = h+ +in-

Limus, too, is an organic weak acid with a red (hin) acid color and a blue (in-) base color, and when the substance is in the range of the indicator's acid, it appears red; In the range of bases, it is shown blue, and when it is neutral, it is shown purple. The chromogenic pH range of litmus is: 8, red when the solution pH < 5, blue when pH > 8, and purple when pH 5 8.

Litmus Molecular formula (C7H7O4N) n is generally replaced by HL or LN (LNH) In acidic solutions: Since [H+] is larger, the equilibrium shifts to the left, and the solution is red. In alkaline solution:

As the [oh-] increases, the equilibrium shifts to the right, and the solution appears blue. Mastery of the equation of reaction is not required in secondary school.

Sulfur dioxide is introduced into the purple litmus solution: the solution turns red.

Reason: SO is passed into the purple litmus solution, which reacts with water to form H so (sulfurous acid), which is acidic, so the purple litmus solution will turn red.

Note: Sulfur dioxide can fade the magenta solution, because the color is restored after heating, because the bleaching principle of sulfur dioxide is that sulfur dioxide reacts with the bleached to form a colorless unstable compound, which destroys the p-quinone formula that plays a role in magenta, and when heated, the compound decomposes and returns to its original color, so the bleaching of sulfur dioxide is also called temporary bleaching.

However, there is no substance in the purple litmus solution that reacts with sulfur dioxide, so it will not fade.

The chemical equation for purple litmus to turn red is: co + h o = h co, carbon dioxide reacts with water to form carbonic acid to turn purple litmus solution red. Litmus is a complex organic compound with a complex structure that is difficult to write about.

The purple litmus test solution turns red when it encounters acid, and generally only describes the phenomenon.

Both litmus and phenolphthalein are acid-base indicators, and they are a weak organic acid. In solution, as the acidity and alkalinity of the solution change, the molecular structure of the indicator changes and shows different colors.

The litmus solution turns red when exposed to acid, CO2+ H2O, H2CO3

The test solution of Shi He Jujube changed back to purple and scattered H2CO3 CO2+ H2O (Condition: Kasen Split Heat).

Silicic acid is a weak acid that is insoluble, put into the purple litmus test solution, the hydrogen ions ionized naturally are very few, and the pH is greater than 5, which cannot make the purple litmus test solution turn red and imitate defeat.

The acidic solution that can make the purple litmus solution red, the alkaline solution can make the purple litmus solution blue, and the neutral solution can not change the color of the purple litmus, and it is still violet.

It should be noted that the acidic solution can make the purple litmus solution red, but the acidic solution is not necessarily acid, it may be salt, such as aluminum sulfate, ammonium nitrate, etc.

Litmus Solution: It is used to help determine the acidity and alkalinity of liquids, but it is impossible to know the exact pH value.