Laboratory protocol for identifying sodium carbonate and sodium bicarbonate

The difference in their thermal stability allows the two substances to be identified.

Supplies] test tubes, small beakers, alcohol lamps.

Iron stands and accessories, catheters, rubber stoppers.

Anhydrous sodium carbonate.

Sodium bicarbonate, clarified lime water.

Operation]1 Put a small amount of the identified white powder in each of the two dry test tubes, set up two sets of instruments as shown, and pour clarified lime water into the beaker.

2. Heat the test tube, and soon you can see that there are water droplets at the nozzle of one of the test tubes, and there are continuous bubbles coming out of the catheter mouth, and the clarified lime water becomes turbid. The tube contains sodium bicarbonate.

3 When the other test tube is just heated, there is no other change except for a few bubbles escaping from the catheter mouth due to the heating of the air, and the lime water does not change turbidity. The tube contains sodium carbonate.

Equation. 2nahco3

heating) Na2CO3 + H2O + CO2

Of course, there is a difference, sodium carbonate is called soda, sodium bicarbonate is called baking soda, baking soda is sodium thiosulfate, sodium carbonate and sodium bicarbonate: both are strong electrolytes, but sodium bicarbonate can undergo hydrolysis reaction in water, and the method to test the two is: add HCL drop by drop to the solution of the two, and the immediate gas is sodium carbicarbonate, which is because carbonate first combines with hydrogen ions to form bicarbonate.

To obtain a purer sodium carbonate solution, a small amount of sodium hydroxide needs to be added to it, and again, the alkalinity of the sodium carbonate solution is stronger than that of sodium bicarbonate, because it can undergo secondary hydrolysis

Take the above two powders respectively, heat them, and pass the produced gas into the clarified lime water, if there are water droplets on the test tube wall, and the gas that can make the clarified lime water turbid is sodium bicarbonate.

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 dissolved in water, measure its pH value, and the size of sodium carbonate.

4. Add hydrochloric acid dropwise, hydrochloric acid dropwise added to sodium bicarbonate solution, and immediately produce closed air bubbles, and drop added to sodium carbonate solution will not produce bubbles.

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 pure good alkali, 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 easy to decompose when heated.

Here's how:

1. Heating method.

When heated, it is sodium bicarbonate that produces a gas that makes the clarified lime water turbid, and vice versa. Before and after heating, it is called its mass, and the one whose mass has decreased is sodium bicarbonate, and vice versa.

2. Gas method.

Take an appropriate amount of two solutions to be identified, and add a small amount of hydrochloric acid to produce bubbles of sodium bicarbonate solution immediately. The slower to produce bubbles is the sodium carbonate solution.

3. Precipitation method.

Take an appropriate amount of two solutions to be identified, add an appropriate amount of barium chloride solution or calcium chloride solution, and the precipitate can be sodium carbonate solution.

4. pH measurement is a dilute solution of the same concentration measured by pH, and the larger pH is sodium carbonate solution.

Sodium carbonate characteristics

The aqueous solution of sodium carbonate is strongly alkaline (pH = and has a certain degree of corrosiveness, which can metacompose with acids, and can also metabolize with some calcium salts and barium salts. There are three types of sodium carbonate containing crystalline water: Na2CO3·H2O, Na2CO3·7H2O, and Na2CO3·10H2O.

It is more stable, but it can also decompose at high temperatures to produce sodium oxide and carbon dioxide.

Long-term exposure to the air can absorb moisture and carbon dioxide in the air, form sodium bicarbonate, and form hard lumps.

The crystalline hydrate of sodium carbonate (Na2CO3·10H2O) is easily weathered in dry air.

The two substances of equal mass are heated separately, and the heated gas is allowed to flow through the dry test tube, and after a period of time, the water beads on the inner wall of the test tube are NaHCO3, and the none-NA2CO3 is NA2CO3

Applied chemical equations:

na2co3 ==na2o+co2

2nahco3 ==na2o+2co2+h20

1) Add a small amount of Na2CO3+HCl=NaHCO3+NaCl dropwise to sodium carbonate

If it's greater than 1:, you'll have carbon dioxide in your hand.

2) Add excess carbon dioxide before leakage to the sodium hydroxide solution.

2naoh+co2=na2co3+h2o na2co3+co2+h2o=2nahco3

3) Directly into the sodium carbonate solution, the skin is cleared of carbon dioxide.

Difference Between Sodium Carbonate and Sodium Bicarbonate:

1. Different common names: Sodium bicarbonate is commonly known as baking soda, also known as raw sodium carbonate or heavy alkali or acid sodium carbonate. Sodium carbonate is also called soda ash, commonly known as soda.

2. Different shapes: sodium bicarbonate It is a white powder. Sodium carbonate is a white powder or fine particle.

3. Different stability: sodium bicarbonate is unstable and easy to decompose when heated, while solid sodium bicarbonate decomposes when heated. Sodium carbonate is heated to 815 °C and melts without decomposition, with strong stability and is not easy to decompose when heated.

4. Different solubility: sodium carbonate is easily soluble in water and exothermic when dissolved. Sodium bicarbonate is slightly less soluble in water than sodium carbonate.

5. The acidity and alkalinity of the aqueous solution are different: the aqueous solution of sodium bicarbonate is slightly alkaline. Sodium carbonate is a strong alkali and weak salt, so its aqueous solution is alkaline.

The inspection of carbentamine imitation sodium Huished includes two parts:

Cation: Na+ does the flame color reaction, if it is yellow, the cation is Na+

Anion: CO3 (2-) detection of excitant fiber, add dilute hydrochloric acid, produce a gas that can make the water edge of the clarified lime turbid.