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Chemistry

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Jhanelle Thomas

on 13 March 2013

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Transcript of Chemistry

Le Chateliers principle can be used to maximize the yield of ammonia under specific conditions which affect equilibrium. Le Chatelier’s Principle and ammonia: uses ? Fractional distillation of N2 from the air In order to get as much ammonia as possible in the equilibrium mixture, you need as high a pressure as possible. 200 atmospheres is a high pressure, but not amazingly high. An increase in pressure would result in a greater yield of ammonia.

This is because the equilibrium would try and counter that change by shifting to the side which produces less pressure in the system(from 4 volumes of gas to 2volumes). The same principle can be applied when using pressure According to Le Chatelier’ss principle by lowering the temperature the yield of ammonia should increase. This is because when the temperature of the system is lowered, it would try to counter that change by producing more heat. This would mean producing more ammonia.




The forward reaction in the Haber process is an exothermic one as heat is released into the environment.
  Explain that for me nuh ? Le who say’s what ? Flow chart of the Haber Process The Haber Process Medium temperature (450 - 500oC)

Very high pressure (~250 atmospheres, ~25,500kPa)

A catalyst (a porous iron catalyst prepared by reducing magnetite, Fe3O4).
(N.B. Osmium is a better catalyst but is very expensive) Conditions required for this process The Haber Process Pressure: 200 atmospheres is a compromise
pressure chosen on economic grounds as high pressures are expensive to produce.

Use of a catalyst: Without a catalyst the reaction would occur at such a slow rate that it wouldn’t be feasible. So a catalyst is used to increase the rate of reaction. Economic considerations One volume of nitrogen gas reacts with 3 volumes of hydrogen gas to form 2 volumes of ammonia in the Haber process. Principles of chemical equilibrium and kinetics The carbon monoxide (CO) in the mixture is oxidized to CO2 using steam and an iron oxide catalyst.


The carbon dioxide is removed using a suitable base leaving only hydrogen and nitrogen in the reaction chamber. Origin of the Nitrogen and the Hydrogen cont’d Nitrogen
- From the air by fractional distillation. (approximately 78.1% of air is nitrogen gas)

Hydrogen
- From methane gas which is reacted with steam. Origin of the Nitrogen and the Hydrogen

The Haber Process is essentially the production of ammonia by catalytically combining nitrogen from the air with hydrogen .
The Haber process ? What is it?
At each pass of the gases through the reactor, only about 15% of the nitrogen and hydrogen is converted to ammonia. (Due to the reaction being reversible)

These unreactive gases are continually recycled and the overall conversion is about 98%. Getting the desired
end product. AMMONIA Increasing the concentration of the reactants increases product yield. This is explained by Le Chatelier’s principle because the increase in concentration of reactants is countered by and increase in product Concentration and Le Chatelier’s principle Le Chateliers principle states: What is Le Chatelier’s principle ? If an equilibrium is subject to a change, the equilibrium will shift in order to minimize the effect of that change. The hydrogen is produced from the natural gas (methane, CH4) by adding steam.


Any excess methane is reacted with air. Origin of the Nitrogen and the Hydrogen cont’d The reaction (Combination of elements) Impact Of Ammonia Industry On Human Health Impact Of Ammonia Industry On The Environment Inhalation: Ammonia is irritating and corrosive.
Exposure to high concentrations of ammonia in air causes immediate burning of the nose, throat and respiratory tract.
This can cause respiratory distress or failure.
The Immediate Health Effects Of Ammonia Exposure This behalves similarly to applying fertilizer to the soil; however, in this case ammonia gas from the air deposits on the leaf or soil surface at the base of the plant and is taken up by the plant.
It results in plan growth similar to that observed with fertilizers. Fertilization of Vegetation The ammonium in the soil disassociates or is nitrified into nitrite (NO2-) or nitrate (NO3-) by nitrifying bacteria, releasing H+ ions into the soil.

If not taken up by biomass and converted to methane, the surplus H+ ions eventually lead to the formation of an acidic soil environment. Soil Acidification Chemical fertilizers usually contain too large a dose of ammonia. As little as 10% may be actually absorbed by the crop and rarely more than 50% of the fertilizer applied makes it into the crop grown.
This can result in eutrophication as the excess ammonia can easily be leeched and contaminate natural water supplies through run-off. Eutrophication Skin or eye contact: Exposure to low concentrations of ammonia in air or solution may produce rapid skin or eye irritation.

Higher concentrations of ammonia may cause severe injury and burns.
The Immediate Health Effects Of Ammonia Exposure cont. Ingestion: Exposure to high concentrations of ammonia from swallowing ammonia solution results in corrosive damage to the:
mouth
throat
stomach The Immediate Health Effects Of Ammonia Exposure cont. Ammonia is classified as a Class-2 poison, this means that it is toxic to humans, animals and the environment. Excessive exposure to ammonia can lead to numerous health problems, including but not limited to:
Increase in both blood pressure and the pulse rate
An altered mental status (i.e. coma) has been known to occur in extreme circumstances.
If ammonia is absorbed in excess, it can result in seizures which occur in increasing frequency and level.
It has also led to a decrease in the production of eggs among animals.
If ingested swelling of the lips, mouth and esophagus is extremely likely to occur.
And the vapors are both irritating and fairly corrosive Health Issues Cleaner: Weak ammonia solutions are also widely used as commercial and household cleaners and detergents. It is so popular because it is generally streak free and is used mainly in the cleaning of glass stainless steel and occasionally a stove. It will usually contain 5 to 10% ammonia. Fertilizer: Most the world’s ammonia is actually being used in the production of fertilizer (almost 85% of all ammonia in the world), but only in either its salt or its solution form. These are Ammonium Nitrate and Ammonium Sulfate.

Ammonium Nitrate is NH4NO3, and is used in high-nitrate fertilizers. It is created by the Acid-Base reaction between Ammonia and Nitrate:
HNO3(aq) + NH3(g) → NH4NO3(aq)

Ammonium Sulfate is (NH4)2SO4 and is used mainly in fertilizer in the reduction of pH of the soil. It is created by Synthetic Ammonia reacting with Sulfuric Acid:
2 NH3 + H2SO4 → (NH4)2SO4 Uses of Ammonia The End Refrigeration: Ammonia is a widely used refrigerant in industrial refrigeration system found in the food, beverage, petro-chemical Other agricultural uses of ammonia exist:
Such as using it as a source of protein in livestock feeds for ruminating animals such as cattle, sheep and goats. 

Ammonia can also be used as a pre-harvest cotton defoliant, an anti-fungal agent on certain fruits and as preservative for the storage of high-moisture corn.   Ammonia The pulp and paper industry use ammonia for pulping wood and as a casein dispersant in the coating of paper.

The food and beverage industry use ammonia as a nitrogen source needed by yeast and microorganisms.
  
The textile industry uses ammonia in the manufacture of synthetic fibers such as nylon and rayon.



The plastics industry uses ammonia in the manufacture of phenolics and polyurethanes.   Ammonia is directly or indirectly the precursor to most nitrogen-containing compounds. Virtually all synthetic nitrogen compounds are derived from ammonia. An important derivative is nitric acid.

Therefore ammonia is used in a wide range of industries.
Some of the industries it is employed in are:
Agriculture
Textile
Pharmaceuticals
Mining
Plastic
Food
etc. Industrial Uses of NH3 and cold storage industries. For example it is used in the industrial refrigeration of ice hockey rinks and similar applications because of its favourable vaporization products. Ammonia is used by the leather industry as a curing agent, as a slime and mold preventative in tanning liquors and as a protective agent for leathers and furs in storage. Ammonia is used by the ammonia-soda industry for producing soda ash.

Ammonia is used in the manufacture of certain dyes and applied in the dyeing and scouring of cotton, wool and silk.   The pharmaceutical industry uses ammonia in the manufacture of certain products such as vitamins and cosmetics.



The petroleum industry utilizes ammonia to neutralize acid constituents of crude oil and to protect equipment from corrosion.

The mining industry uses ammonia in the extraction of certain metals such as copper, nickel and molybdenum from their ores.

The rubber industry uses ammonia to prevent premature coagulation by stabilizing natural and synthetic latex during transportation from plantation to factory. Industrial uses of Ammonia Given that the Haber process requires temperatures of 400 - 550C and pressures of 200 - 300 atmospheres it's not surprising that it uses a lot of energy. Manufacture of nitrogen fertilizers uses about 5% of the world's natural gas production, equivalent to 1-2% of the world's annual energy consumption Our impact on the nitrogen cycle is larger than our impact on the carbon cycle.

We add an estimated 140 million tons of fixed nitrogen of which roughly 80-100 million tons is from the Haber process chemical plants. Imbalances in the nitrogen cycle The End The reaction is reversible.
The production of ammonia is exothermic. (releases -92.4kJ/mol of energy). Explosives: Ammonium Nitrate (typically used as fertilizer) is also used in explosives. It is a strong oxidant and upon ignition can react violently with combustible and reducing agents.It is usually used in combination with fuels and more sensitive explosives. For example:
ANFO, a mixture typically consisting of 94 per cent ammonium nitrate and 6 per cent fuel oil,
Amatol is a mixture of roughly equal amounts of TNT and ammonium nitrate. In a grass plains environment, changes may be subtle; however, in natural or mountain areas, changes in plant species may be more obvious, promoting weedy plants while choking out native plants and wild flowers or promoting grasses and sages. Eutrophication generally promotes excessive plant growth and decay, favors certain weedy species over others, and is likely to cause severe reductions in water quality. In aquatic environments, enhanced growth of choking aquatic vegetation or algal
blooms disrupt normal functioning of the ecosystem,
causing problems such as a lack of oxygen in the water,
needed for fish and other aquatic life to survive. The water
then becomes cloudy, colored a shade of green, yellow, brown, or red. This acidic environment can have a negative impact on the plants as well as microorganisms in the soil, who depend on pH in the soil to be maintained within a small range, in order to function optimally. Humans convert more N2 gas is into fixed reactive forms than all the Earth's processes combined.

Synthetic nitrogen fertilizer production, vehicle exhaust emissions and even growing nitrogen fixing crops all fix nitrogen.
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