Chemistry comprehensive practice activities in junior high school self made indicators

The following information is available for reference:

Thymol blue red-yellow yellow-blue indicator is ground well with the solution and diluted into 100ml with water

Methyl orange red-yellow Dissolve methyl orange in 100ml of hot water.

Bromophenol Blue Yellow-Violet Blue Bromophenol blue is ground evenly with 3ml of NaOH solution and diluted into 100ml with water

Bromocresol yellow-blue indicator was ground together with NaOH solution and diluted with water to make 100ml

Methyl red red-yellow Dissolve methyl red in 60 ml of ethanol and add water to 100 ml

Neutral Red Red-Yellow-Orange Dissolve neutral red in ethanol and add water to 100ml

Phenolphthalein 1% colorless-light red Dissolve 1g of phenolphthalein in 90 ml of ethanol and add water to 100 ml

Thymolphthalein colorless-blue Dissolve the indicator in 90 ml of ethanol and add water to 100 ml

Alizarin Yellow Mix Indicator Yellow-Violet Dissolve alizarin yellow in 100 ml of water.

Methyl red-bromocresol green Red-green 3 parts bromocresol green ethanol solution mixed with 1 part methyl red ethanol solution.

Thymolphthalein-Alizarin Yellow R Yellow-Violet Dissolve alizarin yellow and thymolphthalein in 100 ml of ethanol.

Cresol red-thymol blue yellow-violet 1 part cresol red sodium saline solution and 3 parts thymol blue sodium saline solution.

Methyl yellow red-yellow indicator dissolved in 100 ml of 90% ethanol.

Phenol Red Yellow-Red Phenol red is dissolved in 100ml of 60% ethanol.

Now chemistry is going to do this? I'm getting old......I haven't studied it. Congratulations to LZ on his success.

It's a fun experiment, so why not try it out and maybe you'll fall in love with chemistry.

Do the experiment yourself, otherwise what others say will not be impressive.

In fact, it can be, but the effect is different The pigments of apples and carrots are carotenoids, and they change color when exposed to acid and alkali but do not seem to be very obvious......The purple color of seaweed is its photosynthetic pigment, and phycobilin, phycoerythrin, and the like cannot seem to be acid-base indicators......Grapes can, because there are anthocyanins Anthocyanins turn red when acid, and turn blue when alkalin, which can be used as acid-base indicators Many plant flowers, leaves, and fruits contain anthocyanins Purple morning glory, purple sweet potato and other purple-red plant organs have anthocyanins In addition, there is a commonly used type of litmus It is extracted from a lichen called litmus, but now it has been synthesized Hope it can help you, if you have a problem, we will continue**

a Marble and dilute sulphuric acid (with gas released).

b Lime water and dilute hydrochloric acid.

cRust and dilute sulfuric acid (rust disappears).

DMG and dilute sulfuric acid (with gas discharged).

So choose B

A starts to have bubbles, and then the reaction speed gets slower and slower.

b. No obvious phenomenon Acid-base indicator is required.

c. The solution changes from colorless to yellow and bubbles emerge.

d. A large number of bubbles bubbles.

So only b needs an acid-base indicator.

b This reaction is not obvious.

There are bubbles in a to produce an illustrative reaction.

c. The dissolution and disappearance of rust indicates a reaction.

d. There are bubbles to produce an illustrative reaction.

b.The other 3 have gas emitted and can be distinguished.

ca(oh)2+h2so4=caso4+2h2oa(caco3+h2so4===caso4+h2o+co2)c(fe+h2so4=feso4+h2)

d(mg+h2so4=mgso4+h2)

b, the others have obvious phenomena.

b, the other three have phenomena.

I remember the teacher said that purple litmus was made from a flower called litmus.

The discoloration of the acid-base indicator is the color change of the acid-base indicator when it encounters hydrogen ions, or hydroxide ions, and generates new ions. Let the acid-base indicator be A, A+H+=Ah+, A becomes Ah+, and the color is changed.

The reason is the same as above, set the acid-base indicator as a, a+oh- = aoh-, a becomes aoh-, turns blue, and then adds drops of dilute hydrochloric acid, aoh-+h+=a+h2o, to neutral, and then add dilute hydrochloric acid a+h+=ah+, it can still turn red.

Dilute sulfuric acid is not dehydrated or absorbent.

1. Only the discoloration of the indicator is the structure of the indicator.

2. The litmus test solution can react with sodium hydroxide and dilute hydrochloric acid, and they are both reversible, and the structure of the products after acid and alkali reaction is different, so the color is also different.

3. Dilute sulfuric acid has no dehydration and water absorption.

1。There is a dynamic equilibrium in the indicator, and the equilibrium will move in a certain direction after adding acid or alkali, so that the composition of the indicator solution will change, and it will show an undesirable color.

3。You're right.

Indicates that the alkali has changed color; The indicated chemical structure is varied; Dilute sulfuric acid does not.

1. The indicator has a chemical reaction that changes color.

2. When the litmus test solution reacts with hydroxide, a new substance is generated, this substance is blue, and when the substance reacts with an appropriate amount of hydrogen ions, it will generate purple litmus, and when it reacts with excess hydrogen ions, a red substance is generated, which is a balanced reaction, and the reaction conditions are different.

3. No, only concentrated sulfuric acid is available.

1.The indicator is discolored because the structure of the indicator is different under different acids and alkalis, resulting in different colors.

2.The so-called color-changing reaction of the indicator is a reversible reaction, to put it bluntly, the reaction can be carried out under different conditions, or it can be carried out in reverse, the litmus indicator is red to blue under alkaline, but the reaction is reversed under acidity, and the color is restored.

3.Not. Concentrated sulfuric acid is available.

1.It's just a discoloration of the indicator.

2.The indicator discoloration reaction does not refer to the indicator and reactant reaction. It's the reactant you add that makes the indicator change.

The reactants and indicators themselves have not changed. The litmus solution sodium hydroxide reacts to turn blue, and after adding dilute hydrochloric acid, dilute hydrochloric acid and sodium hydroxide react off. Both are gone.

The litmus solution changes back to its original color.

3.Concentrated sulfuric acid has water absorption and dehydration (whether it is water absorption or dehydration depends on the environment), for example, concentrated sulfuric acid is used to dry gas, which is water absorption. If concentrated sulfuric acid is dropped on white paper, the part of the white paper with concentrated sulfuric acid turns black, which is dehydration.

Hope this helps you.

Indicator discoloration is a reversible reaction ......The color displayed is only related to the pH, because the pH value corresponds to the degree of reaction between the hydrogen ion and the indicator, and the direction and degree of the reaction will change accordingly depending on the pH. Therefore, at a certain pH, the degree to which the reaction proceeds must be the same and fixed, because for the same reaction equation, the value of the equilibrium constant is always only related to temperature.

If dilute hydrochloric acid is added, the pH will be lowered, and the reaction will be reversed, and of course it will turn red......There is no such thing as a reversible reaction to the end, only a chemical equilibrium point. When you go to high school, you will basically understand these kinds of questions, and when you go to college, you will find that my words are wrong......Because in fact, it is also related to the side reaction coefficient.

By the way, it's not an indicator that changes color, and it can even be said that it's not. In fact, the indicator appears one color when combined with hydrogen ions and another color when separated. There are two substances before and after the indicator is combined with hydrogen ions, and there is no discoloration of one substance.

It's a mortar. The ratio is one to one, because both ethanol and water are used in moderation. In the case of litmus, litmus is partially soluble in water, but completely soluble in ethanol.

We generally need water as a solvent solution, but light water cannot dissolve all the litmus, so we need to use alcohol, and experiments have proved that the ratio of 1:1 is proper.

The amount of alcohol added should depend on the number of plants such as flower petals.

Chemicals that change color in plants are extracted.

You're talking about the summer vacation in-situ eggplant

Take a small amount of white rice vinegar, water, and water dissolved in edible alkaline noodles, and add an appropriate amount of homemade vegetable acid-base indicator respectively, (such as Yueji, purple cabbage hand branches to make trembling potatoes) list to record the color presented.

Use purple cabbage or purple morning glory: rice vinegar is red, water is purple unchanged, and edible alkaline noodles are blue.

It depends on what plants you use, different plants are different. You can pick some flowers and try them yourself.