Ammonium sulfate. Ammonium sulfate (ammonium sulfate) Nh4 2 so4 decomposition

DEFINITION

Ammonium sulfate is a white substance (Fig. 1), the crystals of which decompose when heated.

It is highly soluble in water (hydrolyzes into the cation). Does not form crystalline hydrates.

Rice. 1. Ammonium sulfate. Appearance.

Table 1. Physical properties of ammonium sulfate.

Preparation of ammonium sulfate

There are industrial and laboratory methods for producing ammonium sulfate. In the first case, the reaction of neutralizing sulfuric acid with synthetic ammonia is used. In addition, flue gases from power plants and sulfuric acid production are used as raw materials for the production of this substance.

The main laboratory method for producing ammonium sulfate is the reaction between concentrated sulfuric acid and ammonia:

H 2 SO 4 + 2NH 3 = (NH 4) 2 SO 4.

Chemical properties of ammonium sulfate

Ammonium sulfate is a medium salt formed by a weak base - ammonium hydroxide (NH 4 OH) and a strong acid - sulfuric acid (H 2 SO 4). It hydrolyzes into the cation. The nature of the aqueous solution of ammonia sulfate is acidic. The hydrolysis equation will look like this:

(NH 4) 2 SO 4 ↔ 2NH 4 + + SO 4 2-;

NH 4 + + SO 4 2- + HOH ↔ NH 4 OH + SO 4 2- + H +;

(NH 4) 2 SO 4 + 2HOH ↔ 2NH 4 OH + H 2 SO 4.

Ammonium sulfate enters into exchange reactions with acids, alkalis and other salts:

(NH 4) 2 SO 4 + H 2 SO 4 (conc) = 2NH 4 HSO 4;

(NH 4) 2 SO 4 + 2NaOH conc = Na 2 SO 4 + 2NH 3 + 2H 2 O;

(NH 4) 2 SO 4 + BaCl 2 = BaSO 4 ↓ + 2NH 4 Cl.

Ammonium sulfate is oxidized by potassium permanganate and potassium dichromate:

(NH 4) 2 SO 4 + 2KMnO 4 = 2MnO 2 ↓ + N 2 + 4H 2 O;

(NH 4) 2 SO 4 + K 2 Cr 2 O 7 = N 2 + Cr 2 O 3 + K 2 SO 4 + 4H 2 O (t = 250 - 350 o C).

When heated to a temperature of 235 - 357 o C, ammonium sulfate decomposes into ammonium hydrogen sulfate and ammonia:

(NH 4) 2 SO 4 = NH 4 HSO 4 + NH 3.

Application of ammonium sulfate

Ammonium sulfate has found wide application in various industries, such as the production of mineral fertilizers, textiles (viscose fiber), powder fire extinguishers, as well as in the food industry (additive E517) and biochemistry.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Exercise

Calculate the mass of sulfuric acid that will be required to obtain ammonium sulfate weighing 7.9 g by reaction with ammonia.

Solution

Let us write down the equation for the reaction between sulfuric acid and ammonia to form ammonium sulfate:

2NH 3 + H 2 SO 4 = (NH 4) 2 SO 4.

Let's calculate the number of moles of ammonium sulfate (molar mass - 132 g/mol):

n ((NH 4) 2 SO 4) = m ((NH 4) 2 SO 4) / M ((NH 4) 2 SO 4);

n ((NH 4) 2 SO 4) = 7.9 / 132 = 0.06 mol.

According to the reaction equation n((NH 4) 2 SO 4): n(H 2 SO 4) = 1:1, which means

n(H 2 SO 4) = n((NH 4) 2 SO 4) = 0.06 mol.

The mass of sulfuric acid that is required to obtain ammonium sulfate by reaction with ammonia is equal to (molar mass - 98 g/mol):

m (H 2 SO 4) = n (H 2 SO 4) × M (H 2 SO 4);

m (H 2 SO 4) = 0.06 × 98 = 5.88 g.

Answer

The mass of sulfuric acid is 5.88 g.

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Physical and chemical properties

Ammonium sulfate (NH 4) 2 SO 4 - colorless crystals, density - 1.766 g/cm 3. At temperatures above +100°C it decomposes with the release of ammonia NH 3 and the formation first of NH 4 HSO 4, and subsequently (NH 4) 2 S 2 O 7 and sulfanilic acid.

Solubility in water: at 0°C - 70.5 g/100 g, at +25°C - 76.4 g/100 g, at +100°C - 101.7 g/100 g. Oxidizes to N 2 under by the action of strong oxidizing agents, for example, potassium permanganate KMnO 4.

Ammonium sulfate contains:

nitrogen by mass fraction in terms of dry matter - not less than 21%;
water - 0.2%;
sulfuric acid - no more than 0.03%.

Fractional composition of the fertilizer:

mass fraction of fractions larger than 0.5 mm - no less than 80%;
less than 6 mm - 100%.

Friability - 100%.

The mass fraction of the residue insoluble in water does not exceed 0.02%.

Application

Agriculture

Ammonium sulfate in agriculture is used as the main fertilizer for various crops.

Industry

Ammonium sulfate in the chemical industry is used as a component of the precipitation bath in the formation of viscose fiber. In the glass industry - as an additive to glass batch to improve its fusibility.

Behavior in soil

When applied to the soil, ammonium sulfate quickly dissolves, and a significant part of the NH 4 + cations enters the soil-absorbing complex. At the same time, an equivalent amount of displaced cations passes into the soil solution. In this case, the ammonium ion loses its mobility. This eliminates the risk of it being washed out during soil leaching.

Being in an exchange-absorbed state, ammonium ions are well absorbed by plants. (Image)

Due to nitrification, ammonium nitrogen turns into nitrate form. The rate of transition of ammonia nitrogen into nitrate nitrogen depends on the conditions necessary for nitrification: temperature, aeration, humidity, biological activity and soil reaction. One of the main factors influencing the rate of nitrification is the degree of soil cultivation.

Waterlogging and increased soil acidity inhibit nitrification. Liming acidic soils significantly speeds up this process. After ammonium nitrogen is converted into nitrate nitrogen, it acquires all the properties of nitrate fertilizers. As a result of the nitrification process, nitric acid is formed in the soil and sulfuric acid is released.

(NH 4) 2 SO 4 + 4O 2 → 2HNO 3 + H 2 SO 4 + 2H 2 O

In the soil, these acids are neutralized by interacting with bicarbonates of the soil solution and cations of the soil absorption complex.

Neutralization of mineral acids is accompanied by the use of bicarbonates of the soil solution and the displacement of bases from the PPC by hydrogen. This weakens the buffering capacity of soils and increases their acidity.

A single application of ammonium sulfate may not affect the soil reaction. With the systematic use of this fertilizer, the soil environment can become significantly acidic. The degree of acidification increases with lower buffer capacity of soils.

Application on various types of soils

When used for a long time, ammonium sulfate has an oxidizing effect on the soil.

On acidic soils

The oxidizing effect of this fertilizer becomes evident after just a few years. To regulate the soil reaction and enhance the effect of the fertilizer, it is recommended to carry out liming or neutralize ammonium sulfate before applying it to the soil. To do this, add 1.3 quintals of lime per 1 quintal of fertilizer.

On black soils

soil acidity increases after 10-15 years. However, acidification of chernozems has virtually no effect on productivity, since these types of soils have a high humus content, high buffering capacity and absorption capacity.

On chestnut soils

and sierozems there is no reason to fear acidification of carbonate soils.

On light soils

in areas of sufficient moisture, ammonium sulfate is most effective due to the weak migration of ammonium.

Methods of application

Ammonium sulfate is most suitable for. But it is also acceptable to use for surface winter grain crops, hayfields and pastures, as well as

Ammonium sulfate is an ammonium inorganic salt of sulfuric acid containing 21% nitrogen in the form of ammonium cations and 24% sulfur in the form of sulfate anions. Ammonium sulfate is often used as a fertilizer for alkaline soil.

Ammonium sulfate occurs in the form of colorless crystals or small white hygroscopic granules.

Ammonium sulfate, also known as diammonium sulfate or sulfuric acid salt, is an odorless, white crystalline substance that tastes salty. The compound is readily soluble in water, but insoluble in alcohol or acetone.

Obtaining ammonium sulfate in laboratory conditions is possible by exposing a concentrated solution of H2SO4 to concentrated sulfuric acid 2NH3.

It is also possible to produce ammonium sulfate by introducing ammonia gas into hot gases.

Ammonium sulfate decomposes when heated to 250°C. If the substance is heated to a higher temperature, it will decompose into ammonia, nitrogen, sulfur dioxide and water.

Application of ammonium sulfate

The main use of ammonium sulfate is as a fertilizer for alkaline soil. In the soil, ammonium sulfate ions are released and form a small amount of acid, which lowers the soil and at the same time saturates the necessary nitrogen for better plant growth. The main disadvantage of using ammonium sulfate is the low nitrogen content compared to ammonium nitrate.

Ammonium sulfate is also widely used as an agricultural spray and an adjuvant for water-soluble insecticides, herbicides and fungicides. It functions as a binder for iron and calcium cations that are present in water and plant cells. The substance is particularly effective as an adjuvant for glyphosate and glufosinate herbicides.

In biochemistry, reprecipitation with ammonium sulfate is a method for purifying proteins. Ammonium sulfate is soluble in water and therefore can be used to create concentrated solutions that can purify proteins, causing their concentrated precipitation. It is a convenient and simple method for fractionating complex mixtures of proteins, which is why ammonium sulfate is used as an ingredient in many diphtheria, tetanus and pertussis vaccines.

In the food industry, ammonium sulfate is used as a food additive E517, which is used as an acidity regulator for flour and bread and is considered safe for consumption.

Ammonium sulfate is also used to produce other ammonium salts, especially ammonium persulfate.

Homemade explosives are made using ammonium sulfate.

Ammonium sulfate is a component of powder fire extinguishers and fire retardants.

Ammonium sulfate is very popular in Japan, Southeast Asia, as well as northeast China and other rice growing areas. It is used as a fertilizer for growing rice, tea, herbs, vegetables, fruits and grains. Ammonium sulfate is more effective than urea, ammonium bicarbonate, ammonium chloride and ammonium nitrate.

As feed additives, ammonium sulfate provides non-protein nitrogen nutrients to ruminants. Ammonium sulfate is also used in some areas of fish farming.

Properties of ammonium sulfate

Crystalline substance insoluble in acetone, ethanol and ether.

The density of ammonium sulfate is 1.77 g per 1 ml, storage temperature is 2-8 ° C, solubility in water is 77 g per 100 ml.

The main property of ammonium sulfate is its stability, however, upon contact with strong oxidizing agents, a fire or explosion may occur.

Harm of ammonium sulfate

Inhalation of ammonium sulfate vapor may cause severe irritation and inflammation of the respiratory tract. Ingestion of ammonium sulfate causes irritation of the gastrointestinal tract, accompanied by nausea, vomiting and diarrhea. When ammonium sulfate comes into contact with the skin or eyes, irritation, redness, itching and pain may occur.

Ammonium sulfate is safe to use in well-ventilated areas using safety glasses and full-face masks, boots, gloves, aprons or coveralls made of impervious material such as PVC.