1-Describe and explain the structure of ammonium ion and its formation by acid base reactions
The ammonium ion is a positively charged poly-atomic ion and has the chemical formula of NH+. It is formed due to the protonation of ammonia (NH3).
The lone pair on the (N) in ammonia forms a bond with proton (H+). Thereafter, all four N–H bonds are equivalent, and are polar covalent bonds. Ammonium ion has a tetrahedral shape and is isoelectronic (having same number of electrons) with methane and borohydride.
Ammonium ion is found in a number of salts for example it is found in ammonium carbonate, ammonium chloride and ammonium nitrate. Majority of the simple ammonium salts are soluble in water.
Ammonia is considered to be typically a weak base. It is a Bronsted-Lowry base –( a substance which can accept hydrogen ions). Ammonia is a base because of the lone pair on the nitrogen atom which, very readily, can accept hydrogen ions. It can react with water (as shown in the diagram below) by removing H+ ion from a water molecule to produce ammonium ions and hydroxide ions. A co-ordinate dative covalent bond is formed between the nitrogen and hydrogen ion.
Ammonia also can react with other acids to form ammonium salts. For example, ammonia can react with hydrogen chloride gas in a acid-base reaction:
When the ammonium ion is formed the 4th hydrogen atom is attached by a dative covalent bond because only the hydrogen’s nucleus is transferred from the chlorine atom to the nitrogen atom. The hydrogen’s electron is left on the chlorine atom to form a negative charged chloride ion.
Once the ammonium ion has formed it is hard to tell difference between dative covalent and the ordinary covalent bonds. Although the electrons are shown differently in the diagram, there is no difference between them in reality.
2-Acidity and basicity of ammonia
Ammonia is a very common liquid that is used in every household and industry processes it can easily be identified due to its distinctive odor. Majority of ammonia’s uses and benefits come from its pH level. A molecule of ammonia contains a negatively charged nitrogen ion and also three positively charged hydrogen ions, so ammonia has a chemical formula of NH3. The pH of common is around 11. Ammonia is a base, which means it reacts in water to form a positively-charged ammonium (NH4+) ion and a negatively-charged hydroxide (OH-).
Basicity of ammonia
Ammonia is considered to be a weak base because of its chemical structure, the nitrogen atom contains one lone pair, that easily accepts a proton, rather than donating/giving one, that leads to the formation of the ammonium ion. Also ammonia is very soluble in water due to the polarity of the NH3 molecule and its ability to form hydrogen bonds. When it is dissolved in water, ammonia acquires hydrogen ions from the water to produce hydroxide and ammonium ions.
And it is the formation of these hydroxide ions that imparts ammonia’s characteristic basicity. However, because not all dissolved ammonia reacts with water to form ammonium ions; this is why ammonia is called a weak base.
to summarize the above points it can be said that According to the Bronsted-Lowry concept of acids and bases, the acids are proton donors. So ammonia has tge ability to accept A PROTON i.e., hydrogen ion forming ammonium Ion so it’s a base according to that concept. According to Lewis concept of acids and bases , the acids are those species which are electron pair acceptors and bases are electron pair donors , so ammonia is having a central nitrogen atom In its molecule which has a lone pair of electron, so it is electron sufficient that is why it can donate electron pair , so it’s a base according to that concept too
Acidity of ammonia
ammonium ion can also act as a weak acid in aqueous solutions because it breaks down in water to form ammonia and a hydrogen ion. Hence, although ammonia is mostly considered a weak base, it can also act as a weak acid in aqueous solution.But due to the strong evidences provided by the Bronsted-Lowry concept of acids and bases ammonia is considered as a weak base.
Ammonia and amines
Ammonia reacts as a nucleophile with alkyl halides to give primary amines in a nucleophilic substitution reaction.Yields are often poor as the product, a primary amine, RNH2, is itself a nucleophile and can react with more alkyl halide.
The result are mixtures containing primary amines, secondary amines, tertiary amines and quaternary ammonium salts. The halogenOalkane is heated with a concentrated solution of ammonia in ethanol. The reaction is carried out in a sealed tube. You couldn’t heat this mixture under reflux, because the ammonia would simply escape up the condenser as a gas.
3-Manmade and natural occurrence of oxides of nitrogen and their catalytic removal form the exhaust gases of internal combustion of engine .Nitrous oxide is naturally present in the atmosphere being a part of Earth’s nitrogen cycle, and has a variety of natural sources. Nitrous oxide molecules stay in the atmosphere for about 114 years before they are removed by a sink or destroyed through chemical reactions.
Nitrous oxide emissions occur naturally by many sources eg. from the plants, animals, and microorganisms that live in soil and in water. Nitrogen takes on a variety of chemical forms throughout the nitrogen cycle,.A natural source of nitrogen oxides occurs from the lightning stroke. The very high temperature in the lightning bolt causes the gases oxygen and nitrogen in air to react to form nitric oxide.
The nitric oxide very quickly reacts with more oxygen to form nitrogen dioxide.
At normal standard temperatures oxygen and nitrogen gases do not react. While In the presence of very high temperatures, nitrogen and oxygen do react together and form nitric oxide. These conditions are mostly found in the combustion of coal and oil at the electric power plants, and also during the combustion of gasoline in the automobiles. Both of these sources contribute equally to the formation of nitrogen oxides. In areas where there is high automobile traffic, such as in the large cities, amount of nitrogen oxides emitted in the atmosphere can be very significant. Globally, around 40% of total N2O emissions come from human activities. 20% Nitrous oxide is emitted from agriculture, transportation, and industry activities, described below.
Agriculture. Nitrous oxide can result from agricultural soil management activities such as from the use of synthetic and organic fertilizer and other many cropping practices, the management of manure, or burning of agricultural residues.
Fuel Combustion. Nitrous oxide is also emitted when fuels are burned. The amount of N2O emitted depends on the type of fuel and combustion technology, maintenance, and operating practices.
Industry. Nitrous oxide is generated as a byproduct during the nitric acid production that is used to make synthetic commercial fertilizer, and in the production of adipic acid, that is used to make fibers and other synthetic products.
Use of catalytic converters
For an automobile’s internal combustion engine to operate, a combustion reaction needs to occur inside the vehicle’s engine. But this reaction results in the production of harmful burnt gases that contribute to air pollution. In order to reduce this harmful effect, modern automobiles and cars are equipped with a device catalytic converter which reduces production of three harmful compounds found in the car exhaust:
Carbon monoxide (a poisonous gas)
Nitrogen oxides (a cause of smog and acid rain)
Hydrocarbons (a cause of smog)
Nitrogen oxides (NOx) are broken down into nitrogen gas (N2) and oxygen gas (O2). the catalytic converter uses a reduction catalyst composed of platinum and rhodium to reduce the nitrous oxides. As the nitrous oxide molecules (NO and NO2) pass through the converter, the catalyst removes the nitrogen atom, allowing the free oxygen to form oxygen gas. The nitrogen atom that is attached to the catalyst reacts with other attached nitrogen atoms to form nitrogen gas (N2). Reduction Reaction 1: 2NO => N2 + O2
Reduction Reaction 2: 2NO2 => N2 + 2O2
4-state and explain the environmental consequence of the uncontrolled use of nitrate fertilizers
Gardeners and farmers sometimes need to add nitrogen fertilizer to their gardens and fields to provide the right food for their plants and crops. The amount needed depends on plant and seed instructions and on the other sources of nitrogen, such as manure. Nitrogen at much higher levels causes a loss of certain plant species, depletion of soil nutrients, killing of aquatic organisms, and contamination of drinking water.
The National Science and Technology Council has reported that excess of nitrogen encourages the growth of nonnative grasses and kills lichens on the trees. In the coastal areas of the western United States, soils have higher levels of nitrogen, which feed nonnative grasses. The shift in plant species increases the chances of wildfires because these new grasses are flammable, the ESA explains.
In the soil, too much nitrogen can create an imbalance of nutrients that can causes depletion of other important minerals like calcium, phosphorus and magnesium. Also excess of nitrogen results in this acidification of the soil when acid rain falls. When the nitrogen abundance reduces important minerals, toxic elements such as aluminum can proliferate and harm plants as well as fish in rivers.
When the nitrogen levels in rivers and the streams increase, they help in algae overgrowth. As algae decompose, the organic matter in water increases.This process uses oxygen, causing its level to drop as a result aquatic life might die.