OCR F335 Agriculture and Industry

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F335 Chemistry by Design: Agriculture and Industry
Formulae and Equations
(a) use the concept of amount of substance to perform calculations involving:
Molecular Empirical Formula:
formulae 1. List all the elements in the compound.
2. Underneath them, write their masses.
3. Divide each mass by their molar mass to find how moles there are.
4. Divide each mole by the smallest mole this is your ratio.
5. Make the ratio into the simplest form this is your empirical formula.
Finding the Molecular Formula from Empirical Formula:
1. Find the mass of the overall compound.
2. Find the relative atomic mass of the compound using the empirical formula.
Calculate how many times more the mass is than the relative atomic mass and multiply all
the empirical formula elements by it.
Masses of
reagents Number of Moles = Mass of Substance
Relative Formula Mass
Number of Moles = Number of particles you have
23
Number of particles in a mole (6.02 x 10 )
Volumes of
gases
Number of Moles =
Volume in dm3
24
Concentrations
of solutions
Number of Moles = Concentration x Volume in dm3
Number of Moles =
Concentration x Volume (in cm3)
1000
Percentage 1. Calculate the RFM of the overall molecule.
composition 2. Calculate the RFM for each constituent atom.
3. Percentage Mass = RFM of constituent atom x 100
RFM of the overall molecule
Percentage
yield
Percentage Yield = Actual Mass x100
Theoretical Mass
Balancing
symbol
equations

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F335 Chemistry by Design: Agriculture and Industry
(b) write and interpret balanced chemical equations (including ionic equations) with state symbols
Ionic Equations:
Ionic equation are only used for precipitation
reactions and only the reactants that are involved
in the reaction are written. The other ions are
called spectator ions .
e.g.…read more

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F335 Chemistry by Design: Agriculture and Industry
Bonding and Structure
(d) suggest and explain the properties of substances in terms of their structure and bonding and position of
their elements in the Periodic Table; draw and use simple electron `dotandcross' diagrams to show
how atoms bond through ionic, covalent and dative covalent bonds and be able to describe a simple
model of metallic bonding;
Ionic Bonding: Covalent Bonding:
Between metals and nonmetals . Between nonmetals .
Elements gain or Electrons are shared .…read more

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F335 Chemistry by Design: Agriculture and Industry
Bonding 2 3 4 3 2 5 6
Pairs
Lone 0 0 0 1 2 0 0
Pairs
Bond
180o
120o Approx 109o
Approx 109o
Approx 109o
90o
and 120o
90o
Angle
Rates of Reaction
(f) describe and explain the effect of temperature, pressure and catalysts on the rate of reaction.
Temperatur Increasing the temperature increases the rate of reaction .…read more

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F335 Chemistry by Design: Agriculture and Industry
Concentratio No effect on the equilibrium constant.
n
Pressure No effect on the equilibrium constant.
Temperature If the temperature change means that more products are formed, the equilibrium constant
will increase.
If the temperature change means that more reactants are formed, the equilibrium constant
will decrease .
Catalyst No effect on the equilibrium constant.…read more

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F335 Chemistry by Design: Agriculture and Industry
+
Ammonium ions NH4 (aq) 3 Bacteria and microorganisms in the soil
Nitrate(III) ions NO2 (aq) +3 Nitrifying bacteria in the soil, bacteria in root
nodules
Nitrate(V) ions NO3(aq) +5 Nitrifying bacteria in the soil, bacteria in root
nodules
Nitrate(I) oxide N
2O (g) +1 Denitrifying bacteria in soil
Nitrogen(II) oxide
NO(g) +2 Thunderstorms, car engines, denitrifying bacteria in
soil
Nitrogen(IV) oxide NO2(g) +4 Oxidation of NO in the atmosphere
Addition to soil Nitrogenfixing Some bacteria in the…read more

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F335 Chemistry by Design: Agriculture and Industry
Inorganic Chemistry and the Periodic Table
(l) recall the following aspects of nitrogen chemistry: structure and bonding in nitrogen gas, ammonia and
the ammonium ion, the appearance and names of the oxides of nitrogen, N 2O, NO, NO
2
Nitrogen Gas (N2):
Nitrate(I) Oxide (N2O):
The low reactivity of N2 molecule arises from the strong
Appearance: Colourless gas.
triple bond.
Source: Denitrifying bacteria in the soil.…read more

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F335 Chemistry by Design: Agriculture and Industry
(m) calculate from given data the percentage yield and atom economy of an industrial process and suggest
the effect of the process on the environment
Percentage Yield Atom Economy
Actual Mass Mass of useful product
P ercentage Y ield = Theoretical Mass × 100
Atom Economy = Total mass of all reactants × 100
The percentage yield tells you how efficient the process is The atom economy tells you what proportion of the reactants
under a particular set…read more

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F335 Chemistry by Design: Agriculture and Industry
(p) discuss the facts and ethics associated with the ways in which chemists are involved in developments to
improve food production, including:
(i) providing extra nutrients
Adding fertiliser to the soil provides crops with extra nutrients , improving plant growth and increasing crop
yield. However, the overuse of artificial fertilisers can be a problem.
Eutrophication ­ fertilisers can leach into lakes and rivers where they cause excessive algae growth ,
reducing the amount of light available for plants.…read more

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