Agriculture and Industry

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  • Created by: Sabina
  • Created on: 07-04-16 10:22
Why will a reaction not take place unless the particles have enough kinetic energy?
Particles need kinetic energy in order to break the intermolecular bonds holding them together.When bonds broken they can then react with other particles in order to form new bonds
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What is activation enthalpy?
The minimum amount of kinetic energy particles need to react
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What effect does increasing the temperature have on the rate of reaction?
Increasing the temperature gives the particles more kinetic energy this means that they collide more often and as more particles have the activation enthalpy there will be more successful collisions increasing the rate of the reaction
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What effect does increasing the pressure have on the rate of reaction?
By increasing the pressure the particles will be closer together this means that they will collide more often and have more successful collisions which in turn will lead to a faster rate of reaction
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What affect does using a catalyst have on the rate of reaction?
A catalyst will increase the rate of reaction as they provide an alternative route for the particles of lower activation enthalpy. This means that more particles will have the energy to react.
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What is dynamic equilibrium?
When the rate of the forward reaction is equal to the rate of the backwards reaction in a closed system
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What does Le Chantelier's principle state?
If there is a change in conditions the equilibrium will shift in order to counteract the change
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What two factors affect equilibrium?
Temperature and pressure
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What affect does temperature have on equilibrium?
If temperature increases the equilibrium will shift in the endothermic direction in order to absorb the heat. If the temperature decreases the equilibrium will shift in the exothermic direction in order to replace the heat.
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What affect does pressure have on equilibrium?
Increasing the pressure shifts the equilibrium to the side with fewer gas molecules to reduce the pressure. A decrease in pressure causes the equilibrium to shift to the side with more gas molecules in order to raise the pressure.
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What factors need to be considered when designing an industrial process?
Rate of reaction, product yield an cost. These all need to be balanced in order to get the best conditions for the process. The final conditions are usually a compromise between several different factors
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What are the advantages and disadvantages of high temperature in an industrial process?
Reactions got faster at high temperatures so more product will be made. However it also makes the reactions more expensive due to the cost of fuel
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What are the advantages and disadvantages of high pressure in an industrial process?
Make gaseous reactions go faster however to create high pressure gas must be pumped into a reaction vessel.Running the pump uses a lot of energy and is expensive.High pressure can also be dangerous so vessel must be made from strong material (steel)
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What are the advantages and disadvantages of catalysts in an industrial process?
Catalysts can speed up the rate of the reaction at lower temperatures reducing the money spent on fuel are also a good investment as they remain chemically unchanged (don't get used up). However can also be expensive
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What does the Haber process produce?
Ammonia
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What are the conditions used in the Haber process?
400 degrees and 200 atmospheres of pressure
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What is Kc?
An equilibrium constant
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What do you need to calculate the Kc?
The molar concentration of each substance at equilibrium
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What factor will cause a change in the equilibria constants?
Only changes in temperature cause the equilibria constant to change
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How is Kc calculated?
Kc=(D)d(E)e/(A)a(B)b
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How are the units for Kc calculated?
(moldm-3)^2/(moldm-3)^mol(moldm-3)^mol
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What is partial pressure?
The pressure of individual gases in a gas mixture
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When would partial pressures be used?
When dealing with gas-phase equilibria
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How is partial pressure p(A) calculated?
number of moles of A/total number of moles of gas x total pressure of the mixtureHo
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How is Kp calculated?
p(D)d p(E)e/p(A)a p(B)b
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Why is nitrogen very unreactive?
Nitrogen has 5 electrons in its outer shell as it is in group 5. They form diatomic molecules (N2) in order to get a full outer shell this is done by them forming triple bonds with another nitrogen. This triple bond is very difficult to break.
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How is ammonia (NH3) formed?
N2 reacts with H2. The nitrogen forms covalent bonds with 3 H atoms leaving a lone pair of electrons on the nitrogen
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What makes ammonia soluble in water?
Ammonia is able to form hydrogen bonds between molecules
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What allows ammonia to act as a ligand?
The lone pair of electrons on the N means that ammonia is able to form dative covalent bonds. Allowing it to act as a ligand forming complex ions with transition metals
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How are ammonium ions formed?
The lone pair of N means that it is a base. It forms covalent bonds with protons to form an ammonium ion (NH4+)
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What are the different oxides formed by nitrogen and what are their properties?
Nitrogen Monoxide (NO)-Is a colourless gas Dinitrogen Monoxide(N2O)-Is a colourless gas with a sweat smell Nitrogen Dioxide(NO2)-Brown gas, has a sharp odour and is toxic
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What is nitrogen used for by plants and animals?
To make proteins
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What form is N2 and what produces this form of nitrogen?
It is nitrogen in the air and it is produced by dentrifying bacteria
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What form is NH4+ and what produces this form of nitrogen?
It is ammonia ions in the soil and it is produces by bacteria and micro-organisms in the soil
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What form is NO3^- and what produces this form of nitrogen?
It is Nitrate(V) ions in the soil. It is produced by nutrifying bacteria in the soil and bacteria in root nodules
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What form is NO2^- and what produces this form of nitrogen?
It is Nitrate(V) ions in the soil. It is produced by nutrifying bacteria in the soil and bacteria in root nodules
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What form is NO and what produces this form of nitrogen?
Nitrogen(II) oxide. It is produced by thunderstorms, car engines and dentrifying bacteria in the soil
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What form is NO2 and what produces this form of nitrogen?
Nitrogen(VI) oxide. It is produced by the oxidation of NO in the atmosphere
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What form is N2O and what produces this form of nitrogen?
Nitrogen(I) oxide. It is produced by dentrifying bacteria in the soil
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What is the role of the nitrogen cycle?
To convert nitrogen into more accessible forms so that they can be taken in by plants and animals
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What type of reactions occur in the nitrogen cycle
Redox reactions
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How is nitrogen gas in the air converted into ammonia in the soil?
Through the Haber process and nitrogen-fixing bacteria (N2+3H2-->2NH3)
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How is ammonia in the soil converted into ammonia ions in the soil?
By reduction (NH3+H+-->NH4+)
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How are ammonia ions in the soil converted into nitrate(III) ions in the soil?
By nitrification (NH4^+ +O2-->NO2^-+4H^+ +2e^-)
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How are nitrate(III) ions in the soil converted into nitrate(V) ions in the soil?
By the addition of water during nitrification (NO2^- +H20--> NO3^- +2H^+ +2e^-
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What is nitrification?
The oxidation of ammonia or ammonia to nitrate followed by the oxidation of nitrites to nitrates
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How are Nitrate (V) ions in the soil converted to nitrogen gas in the air?
By dentrification (2NO3^- +10e^- + 12H^+ -->N2 +6H2O)
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How do animals provide ammonia ions?
By excretion, death and decay
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How is nitrogen gas converted into nitrogen oxides?
Lightening and burning of fossil fuels (N2+O2-->2NO
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How does industrial chemical production impact the environment?
Raw material and sources of energy are taken from the Earth and waste products are released into the environment
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Why do less efficient chemical reactions have a greater impact on the environment?
They require more raw materials to make the product and they produce more waste per unit of product made
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What is used to assess the environmental impact of an industrial reaction?
The percentage yield and the atom economy.The higher these are the less impact they are likely to have on the environment
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What does the atom economy tell us?
What proportion of the starting materials end up in the useful products
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How is percentage atom economy calculated?
mass of desired product/total mass of all products x 100 (You can use masses in grams or relative molecular masses)
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What does percentage yield tell us?
How efficient the entire process is under a particular set of conditions
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How is percentage yield calculated?
actual product yield/ theoretical yeild x 100
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What are the costs of producing a chemical?
RAW MATERIALS-chemicals need to be bought for the reaction FUEL/ENERGY-Reactions needing high temperature or pressure will use up a lot of energy also energy used for transportation FIXED COSTS-staff wages,taxes,renting equipment DISPOSAL COSTS
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What are some of the risks involved in chemical production?
Some chemicals are highly flammable and carry the risk of explosion, some are also harmful to our health if we come in contact with them or their vapours and some can also damage the environment
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How can the chemical industry improve food production?
Fertilising the soil, acid neutralisation and killing pests
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How does fertilising the soil improve food production?
Provides crops with the nutrients needed to grow, improving plant growth and increasing crop yield
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What are the disadvantages of fertilising soil?
Rain can wash the fertiliser from the soil into rivers and lakes causing excessive algae growth, this reduces the amount of light available for plants that are needed to oxygenate the water. Nitrate (V) ions can get into drinking water (health risk)
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How does acid neutralisation improve food production?
Crops have an optimum pH. Too much acid in the soil can lead to poor plant growth so chemicals can be added to soils to neutralise acid and improve the growth of the crop
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What chemicals can be added to soil to neutralise it?
Limestone (calcium carbonate) or lime (calcium hydroxide)
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How does killing pests improve food production?
Pesticides can be used to kill insects, weeds or mouldants all of which can reduce crop yield an quility
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What are the disadvantages of the use of pesticides?
Often end up killing non-pest organisms (some of which are beneficial to the crop), some don't break down easily leading to their accumulation in the food chain which can be harmful to organisms and can be washed into drinking water
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Suggest one reason why denitrification is a problem for crop production
Nitrogen less available to crops
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Card 2

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What is activation enthalpy?

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The minimum amount of kinetic energy particles need to react

Card 3

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What effect does increasing the temperature have on the rate of reaction?

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Card 4

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What effect does increasing the pressure have on the rate of reaction?

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Card 5

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What affect does using a catalyst have on the rate of reaction?

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