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Urea Formula – Structure, Properties, Uses, Sample Questions

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  • Last Updated : 30 Jun, 2022

Urea or Carbamide is a nitrogenous compound that is commonly excreted by animals and humans as a waste product of protein metabolism. In 1727 Herman Boerhaave a Dutch chemist discovered urea. Then Friedrich Wohler a German chemist was first to synthesize urea in 1828. He converted ammonium cyanate an inorganic compound into an organic compound from animal sources. It is also called carbamide because of the groups, a carbonyl group attached to two amide groups. Carbonyl group – a carbon atom is double-bonded to an oxygen atom.

Urea is the main component of human urine. Ammonia is converted into urea by the liver and flows into blood. Then kidneys filter the urea and waste compounds from the blood. Now all the waste and urea compounds pass through the urinary tract and are excreted as a form of urine.

Urea is a colorless to white crystalline solid and it is largely used as a fertilizer. It has a density of 1.32 g/cm3. It is a nitrogen-containing compound found in urine. It is formed by the urea cycle. Urea is used as a raw material for animal feed. It has a melting point of 134˚C. Urea can absorb moisture from the atmosphere. It is highly soluble in water and urea as a chemical formula of CO(NH2)2. Urea has ill effects on long-term usage, it can cause damage to the skin. 

Formula of Urea

CO(NH2)2 is the chemical formula of urea. It has a molar mass of 60.06 g/mol. It consists of carbon, nitrogen, oxygen, and hydrogen. It is formed by the two amide groups (-NH2) and is bonded to a carbonyl group (a carbon atom is double-bonded to an oxygen atom, -C=O). 

Structure of Urea

Urea maintains a planar geometry (which means that all of the atoms lie in the same plane) and it is a double amide. All of the bonds are covalent (- means electrons are shared between the atoms of each bond) with nonpolar bonds between carbon and oxygen, carbon and nitrogen.

Urea Structure

Preparation methods for Urea

Urea can be prepared in the laboratory by the reaction of ammonia with carbonyl chloride, 

COCl2 + 2NH3 → CO(NH2)2 + 2HCl

Urea can be prepared by the mixing of liquid ammonia and liquid carbon dioxide. By this reaction, ammonium carbamate is formed. When ammonium carbamate is heated at 130˚to 150˚C at 35 atm pressure as final product urea is formed.

2NH3 + CO2 → NH2COONH4 → CO(NH2)2 + H2

Urea can also be formed by the reaction of ammonia on alkyl carbonates or diethyl carbonate,

(C2H5O)2CO + 2NH3 → CO(NH2)2 + 2C2H5OH

The reaction for the dehydration of carbamate to give urea in accordance with the equation

NH2CO2NH ⇄  (NH2)2CO + H2O

Physical properties of Urea

  • It has a molar mass of 60.06 g/mol.
  • It is a colorless to white crystalline solid.
  • Urea has a density of 1.32 g/cm3.
  • It has a melting point of 134˚C.
  • It can easily be soluble in water and alcohol.
  • It is odorless.
  • Urea is insoluble in ethane.
  • It is a weak base.

Chemical properties Urea

  • When urea reacts with alkaline sodium hypochlorite, hydrazine is produced.

CO(NH2)2 + NaOCl + 2NaOH → N2H4 + NaCl + Na2CO3 + H2O

  • Urea hydrolyses with water it generates isocyanate and ammonia.

CO(NH2)2 + H2O → HNCO + NH3

  • On the former further hydrolyses to another molecule of ammonia and carbonic acid.

HNCO + NH3 → H2CO3 + 2NH3

  • The urease-urea reaction involves a different mechanism, urea hydrolyses into ammonia and ammonium carbamate The ammonium carbamate further hydrolyses to produce another ammonia molecule and carbonic acid.

H2NCOOH + H2O → H2CO3 + 2NH3

  • Urea reacts with sodium hydroxide upon releasing ammonia and sodium carbonate.

NH2CONH2+2NaOH → 2NH3 + Na2CO3

  • Urea nitrate a fertilizer-based high explosive is produced when urea reacts with nitric acid, an exothermic reaction.

HNO3 + (NH2)2CO → (NH2)2COHNO3

Harmful effects and safety measures

  • Urea at elevated temperatures decomposes and forms toxic fumes. It can cause irritation to the eyes and respiratory system.
  • Urea can react vigorously with other chemical compounds such as nitrates and perchlorates.
  • Urea has ill effects on long-term usage, it can cause damage to the skin. Avoid contact with eyes, skin, and clothing.
  • Empty containers of urea retain product residue and can be hazardous. Keep away from clothing, incompatible materials, and combustible materials.

Uses

  • Urea is used in the explosive industry as a stabilizer in nitro explosives.
  • Urea is used in creams as an additive for the rehydration of the skin.
  • It is largely used as fertilizer because of its nitrogen content.
  • Urea is used as an animal feed.
  • Used in the production of the chemical compound hydrazine.
  • It is used as a raw material for pesticides and herbicides and fungicides compounds.
  • Urea is used in laboratories as a protein denaturant.
  • Used in the urea-derived compounds such as urea-formaldehyde, and urea melamine formaldehyde.

Sample Questions

Question 1: What are the applications of urea in the medical industry?

Answer:

Urea is even used in the pharmaceutical industry. Some of the uses are: It is used in the BUN test or blood urea nitrogen test is used to measure the level of amount of the nitrogen present in the blood which comes from urea. Higher levels of urea in the body influence many biological functions like dehydration, liver functionality, and diet.

Urea is used in many creams which helps to treat rough and dry skin problems. Some of the problems include callus, eczema, corns, ingrown nails, and psoriasis. But lower levels of urea should be in usage because of its toxic properties. Urea contains keratolytic properties, it can increase the moisture in the skin which helps from dehydration. Applying to sensitive areas should be avoided.

Question 2: How urea is formed in the industry?

Answer: 

In industry, urea can be prepared by the mixing of liquid ammonia and liquid carbon dioxide. By this reaction, ammonium carbamate is formed. When ammonium carbamate is heated at 130˚to 150˚C at 35 atm pressure as final product urea is formed.

2NH3 + CO2 → NH2COONH4 → CO(NH2)2 + H2O

Question 3: How urea is formed and excreted in the human body?

Answer:

It is the main component of human urine. By the breakdown of the proteins in the body. The body accumulates all the nitrogenous waste compounds. When amino acids are metabolized, they change into ammonia, water, and carbon dioxide. Then the liver converts ammonia to urea and releases it into the blood. Kidneys play important role in the filtration of urea and other parts of waste compounds in the blood. From then all the remaining waste which is filtered out is flown to the urinary tract. Then it passes through the ureters, bladder, and urethra and last it is excreted in the form of urine.

Question 4: What are the preventive and control measures for urea?

Answer:

Urea has toxic properties. Here are the preventive and control measures

  • There should be contaminated protective clothing.
  • Wear proper protection when handling the compound.
  • It should be stored in closed bottles.
  • The stored container should show a correct hazard label, indicating whether it is a dangerous compound.
  • Plastic (PE or PP) bottles are ideal, as they are going to not break if we drop them on a tough surface.
  • Segregation should be in such a way in order that there’s no direct personal contact by personnel who handle, dispose of, or clean the clothing.
  • Quality assurance to determine the completeness of the cleaning procedures should be implemented.

Question 5: Why urea is harmful to the body?

Answer:

Urea is the waste that the kidneys as a role help filter away. Uremia is a side effect of kidney failure. At the point when the kidneys can’t filter waste as expected, it can enter the bloodstream. Higher urea levels propose improper kidney work. This might be because of intense or constant kidney illness. By and large, a high BUN (Blood Urea Nitrogen) level means your kidneys aren’t functioning admirably. Yet, raised BUN can likewise be because of: Dehydration, because of not drinking an adequate number of liquids, or for different reasons. Urinary tract obstruction.

Question 6: Is urea used in barbituric acid?

Answer:

Urea helps in the formation of barbituric acid. When urea reacts with malonic ester it forms barbituric acid. Barbituric acid plays an important role in the laboratory synthesis of riboflavin also known as vitamin B2. It is used in the production of minoxidil a pharmaceutical drug. 5,5-diethylbarbituric acid (barbitone) and 5-phenyl-5-ethylbarbituric acid (phenobarbitone) act as hypnotics and sedatives.

Question 7: What are the applications of urea in different areas?

Answer:

There are many application uses of urea in many areas. Some are,

  • Automobile: In the automobile industry urea is used in SNCR and SCR reactions to decrease NOx pollutants in exhaust gases.
  • Chemical: It is used as a raw material for the manufacturing of two urea-derived compounds such as urea-formaldehyde resins and urea melamine-formaldehyde used in marine plywood.
  • Agriculture: Urea is the highest nitrogen-containing of all nitrogenous fertilizers. It is widely used as fertilizer. It is also used as an animal feed.
  • Explosive: It is used in the making of high explosives. Urea is used in making urea nitrate which is highly explosive. It is also used as a stabilizer in nitrocellulose explosives.
  • Laboratory: Urea is used in the laboratory. It is very useful and can act as a powerful protein denaturant. Increases the protein solubility.

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