Agriculture and Industry

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  • Created by: Gemma
  • Created on: 13-04-14 10:51
Why do ionic substances have high boiling points?
Strong electrostatic forces between oppositely charged ions
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Why do ionic substances conduct electricity when in solution/molten?
The ions are free to move + act independently of one another
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What is the effect of temperature on the rate of reaction?
Increases the frequency of successful collisions + provides reactant particles to have sufficient KE so that when they collide they have enough total KE to overcome activation enthalpy
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What is the effect of pressure on the rate of reaction?
Increases the concentration of gas particles, which in turn increases the frequency of successful collisions
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What is the effect of a catalyst on the rate of reaction?
Speeds up the rate, by creating an alternate reaction pathway , which in turn lowers the activation enthalpy
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What is the equilibrium constant measuring?
Measure how far a reaction proceeds
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What effect does increasing the temp in an exothermic reaction have on Kc
decreases
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What effect does increasing the temp in an endothermic reaction have on Kc
increases
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What effect does lowering the temp in an exothermic reaction have on Kc
increases
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What effect does lowering the temp in an endothermic reaction have on Kc
decreases
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Is Kc affected by a change in pressure?
no
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Is Kc affected by the presence of a catalyst
no
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What is the formula for Kc
Conc of product/Conc of reactants
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What does the most economical operating conditions for an industrial process depend on?
The balance between the position of equilibrium and the rate @ which the equilibrium is reached. Also the cost : fixed (capital) and variable ( running)
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Conditions for the Haber process?
400 degrees , 200 atm, Fe catalyst
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Why isn't the Haber process carried out at 1000atm
could be explosive - therefore dangerous. Also expensive because the vessel would need reinforced materials which are costly
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Why isn't the Haber process carried out at 10 degrees
Not economically viable, the particles wouldn't have sufficient KE to react + so the rate would be incredibly slow
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Why does the rate + equilibrium theory need to be considered when deciding the conditions for a reaction
to obtain the maximum yield that is economically viable + to compromise conditions
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Shape of Nitrogen (N2)
linear
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Shape of Ammonia
pyrimidal
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Shape of Ammonium ion
tetrahedral
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What does the dashed lines on this diagram indicate?
the electrons are delocalised over 2/3 N-O bonds which are equivalent
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Why is the No2- ion and NO3- ion contain a minus charge
Because one of the oxygen molecules have gained an electron from another molecule
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Draw a dot + cross diagram for NO2-
(need to be hand drawn)
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Draw a dot + cross diagram for NO3-
(need to be hand drawn)
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Are there any dative covalent bonds present in NO2-
no
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Are there any dative covalent bonds present in NO3-
yes
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Formula, appearance @ room temp + sources of nitrogen gas
N2 , colourless gas, denitrifying bacteria in the soil
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Formula, appearance @ room temp + sources of nitrogen (II) oxide
NO, colourless gas, combustion, thunderstorms, denitrifying bacteria in soil
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Formula, appearance @ room temp + sources of nitrogen (IV) oxide
NO2, brown + toxic gas, oxidation of NO in air
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Formula, appearance @ room temp + sources of dinitrogen oxide
N2O, colourless gas, denitrifying bacteria in soil
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How could the costs of raw materials be reduced?
have integrated plant which would minimise transportation costs, the state the raw material is brought in ( gas- high pressure cylinder which is expensive solid- melted/molten or mixed with a liquid to form a ****) , also to use one source
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How could the energy costs/efficiency be reduced?
find conditions which give the most economical conversion, recycle unused reactants - saves money + pollution
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Give an example + definition of fixed cost
Fixed costs = costs incurred regardless of output e.g. capital cost (cost of plant) , insurance, labour costs
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Give an example + definition of variable costs
Variable costs = costs related to a unit of production e.g. raw materials, selling + distributing costs , waste disposal
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Definition of co-product
A product made during the reaction along with desired product , which is useful
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Definition of by-product
An unwanted product produced from an unwanted side reaction
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Which conversion occurs during biological fixation of nitrogen
nitrogen ==> ammonium ion
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Which conversion occurs during nitrification
NH4+ ==> NO2-
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Which conversion occurs during denitrification
NH4+ (aq) ==> NO2- (aq)==> NO (g) ==> N2O (g) ==> N2 (g)
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Which conversion occurs during the loss of ammonia gas
Ammonium ==> NH3
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What happens during leaching
mainly NO3- is lost in rainfall, it is not help in the clay/humus in temperate soils
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Why is nitrogen in the soil needed?
Production of AA + proteins for plant growth - for us it is an advantage because it is part of our food chain
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+ & - of HNO3
+ source of nitrogen - causes a change in pH of soil, at a lower pH there is a loss of minerals
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+ & - of NH4+
+ source of nitrogen - causes undesirable plant growth,dissolves in the rain + gets washed away , eutrophication ( algae take up all the oxygen from the pond + other organisms die)
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What's the risk of flammable gases
explosion/fire
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What's the risk of acidic gases
burns
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What's the risk of toxic emission
health risk - breathing
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How to reduce the risk of explosion/fire
store in a flameproof container, extractor fans, incinerators under controlled conditions
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How to reduce the risk of burns
check plant for leaks , pass through alkaline scrubber to neutralise
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How to reduce the risk of health problems
check protocol to minimise emissions, monitor levels of emission, ensure personnel know evacuation route
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+ & - of providing extra nutrient to the soil
+ save money , protect environment - too much and it will be leached out + may enter drinking water, leads to eutrophication of rivers , too little - growth will suffer
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What happens to the soil in alkaline conditions?
the COOH group attached to the clay particle forms COO-K+ and Phenol group forms C6H5O-Ca2+
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What happens to the soil in acidic conditions?
COOH & Phenol - H+ from rain + microbes bind to the anions , displaying the cations which are leached away WHICH IS BAD - THE MINERAL IONS ARE LEACHED . ALSO AL2O3 IS RELEASED WHICH IS TOXIC TO PLANTS
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How can the pH of soil be controlled?
Use Limestone/chalk to make the soil less acidic, the amount depends on the buffering capacity of soil (clay soils has a higher buffering capacity than sandy soils)
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What are the negative of using pesticides
may leach into water supply, may kill useful/beneficial insects , may kill wild plants for beneficial insects, may cause eutrophication, pests may develop resistant through genetic mutation leading to selection for resistant types
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Card 2

Front

Why do ionic substances conduct electricity when in solution/molten?

Back

The ions are free to move + act independently of one another

Card 3

Front

What is the effect of temperature on the rate of reaction?

Back

Preview of the front of card 3

Card 4

Front

What is the effect of pressure on the rate of reaction?

Back

Preview of the front of card 4

Card 5

Front

What is the effect of a catalyst on the rate of reaction?

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Preview of the front of card 5
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