What are the methods to distinguish sodium carbonate from sodium bicarbonate Can it be distinguished

A] 1Solid appearance: There is a distinct difference.

Sodium carbonate --- white powder, the same as white flour;

Sodium bicarbonate --- white crystals, fine-grained table salt;

2.Solid heating method:

Sodium carbonate --- does not decompose when heated;

Sodium bicarbonate - decomposes by heat, and the gas produced passes into the clarified lime water and becomes turbid;

3.Add CaCl2 (or BaCl2) dropwise to the solution

The sodium carbonate solution --- turbid with CaCl2;

Sodium bicarbonate solution - does not change turbidity in case of CaCl2;

4.Dilute hydrochloric acid was added dropwise in the solution "drop by drop": (theoretically, the actual effect is not good) sodium carbonate solution--- very little HCl dropwise added without bubbles, and NaHCO3 was generated;

Sodium bicarbonate solution - a very small amount of HCl dropwise can also produce bubble CO2;

5.phenolphthalein method (provided that the amount and concentration of the two substances are the same; Theoretically, it can, not very well)

At the same concentration, the pH of Na2CO3 is larger and more alkaline.

6.Solubility method (provided that at the same temperature, theoretically possible, the operation is complicated) - take the same amount of water, and gradually add the solids of the two to dissolve until it is just saturated (not easy to judge); See who dissolves more (Na2CO3 has more solubility).

What do you think? You can first prepare solids of the same mass and compare the residual mass after dissolving to saturation.

2,3,4 [Chemistry Methods] are often covered in the exam

In the case of phenolphthalein, the phenomenon is still obvious, and the red color of sodium carbonate can be seen, and the sodium bicarbonate is basically not visible red. There is also the experiment of pyrolysis, which can also be distinguished. Then there is the dropwise addition of hydrochloric acid after dissolving to see which bubbles appear first, and the solution of sodium bicarbonate will appear bubbles first.

It can be reacted with hydrochloric acid, heated, and soluble calcium salts or barium salts added.

I cannot use solubility, and there is no phenomenon.

Phenolphthalein is also not good, and the phenomenon is not much different.

It is better to use hydrochloric acid.

It can be judged by the strength of their alkalinity.

Distinguish between sodium carbonate and sodium hydroxide.

Colorless phenolphthalein is not allowed.

1. Sodium carbonate is a strong alkali and weak salt, which is alkaline in hydrolysis, and adding colorless phenolphthalein solution will make the phenolphthalein solution red.

Na2CO3 + H2O NaHCO3 + NaOH2 and sodium hydroxide are soluble strong alkalis, and the aqueous solution is alkaline.

The phenomenon is the same, so it is impossible to distinguish between them.

3. There are many reagents to identify sodium carbonate and sodium hydroxide.

Such as: drop calcium chloride solution.

Na2CO3 + CaCl2 = CaCO3 + 2NaCl produces a white precipitate, which proves to be sodium carbonate; It does not produce a white precipitate and is sodium hydroxide.

Another example is adding excessive hydrochloric acid.

Na2CO3+2HCl=2NaCl+H2O+CO2 produces bubbles, which proves to be sodium carbonate; It does not produce bubbles, and it turns out to be sodium hydroxide.

There are several ways to distinguish sodium carbonate from sodium bicarbonate:

1. Heating, sodium bicarbonate has poor thermal stability, and sodium bicarbonate can be decomposed.

2. Take the same amount of dissolved in water, and observe which of the two dissolves more, and the solubility of sodium bicarbonate is small.

3. Take the same amount of soluble in water, measure the car without its pH value, and the sodium carbonate is large.

4. Add hydrochloric acid dropwise, and hydrochloric acid dropwise added to sodium bicarbonate solution will immediately produce bubbles, while dropwise added to sodium carbonate solution will not produce bubbles. Extinction.

5. Add calcium chloride solution, use metathesis reaction, sodium carbonate solution reacts with calcium chloride to produce white precipitate, while sodium bicarbonate will not.

Sodium carbonate is commonly known as soda ash, soda, white powder, good thermal stability, and is not easy to decompose when heated.

Sodium bicarbonate, commonly known as baking soda, is a small white crystal, with poor thermal stability, and is easy to be separated and dissolved by heating.