Acid base mixture, drop with purple litmus test solution, what color is it

Acid-base mixture: if the acid is excessive: the purple litmus solution turns red;

If the alkali is excessive: the purple litmus solution turns blue;

If the acid and base are neutralized in the same amount: the purple litmus test solution does not change color and is purple.

Litmus is a commonly used acid-base indicator with a discoloration range between pH = and color;

It is a weak organic acid with a relative molecular weight of 3300, which changes its conjugate structure and changes color under the different actions of acid-base solutions.

That is, in solution, as the acidity and alkalinity of the solution change, its molecular structure changes and presents different color changes:

In acidic solutions, molecules are the main form of their existence, giving the solution a red color; (The balance shifts to the left due to the increase in [h+]).

In the alkaline solution, the ionization equilibrium of litmus hydrolysis shifts to the right, and the acid ions produced by ionization are the main form of its existence, so the solution is blue; (The balance shifts right due to the increase in [oh-]).

In a neutral solution, molecules and acid ions coexist, resulting in a purple color.

Litmus turns red when acid, and turns blue when alkalin, and does not change color in neutral solution. After mixing, the hydroxide ions are mostly blue, and the opposite is red.

Because of the same mass fraction of sodium hydroxide and hydrochloric acid, hydrochloric acid is excessive...

Both are 100g 10% solution, the amount of hydrochloric acid is 10 and the amount of sodium hydroxide is 10 40Therefore, if the hydrochloric acid is excessive, the litmus solution appears red.

Rui: Rui. Second tone.

Dip purple litmus test paper into non-volatile acids to form red litmus test paper;

Purple litmus paper is soaked in sodium carbonate to make blue litmus paper.

Therefore, the principle of use is that litmus turns red when it encounters acid, and it turns blue with alkali.

Red is used to test for alkaline substances, and blue is used to test for acidic substances.

When the blue litmus paper encounters an acidic solution, the acid-base neutralization should turn purple, and the litmus does not change color in the range of PH6 8, and the range between 6 and 8 is purple, so the neutralization is purple.

Water is neutral, and if a neutral reagent is dropped on blue or red litmus, the paper should.

Turn purple!

The red litmus paper turns blue when exposed to alkali.

The blue litmus test paper turns red when it is acid.

The magenta solution will fade when exposed to oxidizing substances, such as chlorine, sulfur dioxide gas, etc.

Summary. The litmus solution turns red when it is acidic and blue when it is alkaline, and dilute hydrochloric acid or dilute sulfuric acid is dropped into the purple litmus solution, and the solution is red; If sodium hydroxide solution is added drop by drop to an appropriate amount, the solution is purple; The litmus solution turns red, which means that dilute hydrochloric acid and dilute sulfuric acid can interact with the purple litmus solution to show red; Then add sodium hydroxide solution drop by drop to an appropriate amount, the solution is purple, indicating that the acid is reacted by the sodium hydroxide solution, indicating that dilute hydrochloric acid and dilute sulfuric acid can react with alkali solution

When testing the acidity and alkalinity of the solution, can the purple litmus solution be directly dropped into dilute acid?

The litmus solution turns red when it is acidic and blue when it is alkaline, and dilute hydrochloric acid or dilute sulfuric acid is dropped into the purple litmus solution, and the solution is red; If sodium hydroxide solution is added drop by drop to an appropriate amount, the solution is purple; The litmus solution turns red, which means that dilute hydrochloric acid and dilute sulfuric acid can interact with the purple litmus solution to show red; Then add sodium hydroxide solution drop by drop to an appropriate amount, the solution is purple, indicating that the acid is reacted by the sodium hydroxide solution, indicating that dilute hydrochloric acid and dilute sulfuric acid can react with alkali solution

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The hydrogen ions dissociated from the acid itself can turn red by reacting with litmus, and litmus can turn red as long as the acidity of the acid is stronger than that of litmus.

Litmus itself is also a mixed solution of weak acid and alkali, when encountering a strong acidic substance, litmus forms the form of acid molecules, which is red, and when encountering a strong alkaline substance, in the form of a weak acid root, it appears blue.

The same is true for other acid-base indicators, different acidity and alkalinity, different forms of existence of weak acid-base, different colors, of course, the pH value of different indicators is different, such as litmus, phenolphthalein, methyl orange, methyl red and so on.

Acids can work with acid-base indicators!!

Can make purple litmus solution red!

Colorless phenolphthalein does not change color!

Purple litmus turns red when it is acid, blue when it is alkaline, blue when it is alkaline salt, and does not change color when it is neutral salt.

Colorless phenolphthalein does not change when it meets acid, turns red when it is alkaline, turns red when it is alkaline salt, and does not change color when it encounters neutral salt.

Color performance under different pH values.

Litmus Red < 5 "Purple < 8 "Blue."

Phenolphthalein No < 8 "Light Red< 10 "Red.

Experimental preparation: 1. Inject about 150ml of distilled water into a 250ml beaker, add half a tablespoon of litmus powder, heat slightly to 50 60, stir to accelerate the dissolution into a dark blue-purple litmus solution (stock solution), and set aside.

2. Inject 1 2 volumes of distilled water into the test tube, pass into CO to make a saturated CO aqueous solution (HC CO), and set aside.

Preparation of purple litmus: Under the condition of continuous oscillation, saturated CO aqueous solution is added drop by drop to the blue-purple litmus stock solution until the solution changes from blue-purple to pure purple.

To prepare purple litmus liquid, you can also use extremely dilute H Po to replace saturated CO aqueous solution (but do not use strong acids such as H so and HCl); If the H po is slightly excessive, it will be mixed into a red litmus solution.