OCR F332 Elements from the Sea

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Chemistry of Natural Resources: Elements from the Sea
Formulae, equations and amount of substance
(a) use the concept of amount of substance to perform calculations involving:
Molecular Add up the relative atomic mass of the atoms
Formulae
Percentage Yield Percentage yield = Actual Yield x100
Theoretical Yield
Example: 30g of calcium carbonate is heated to produce 14.5g of calcium oxide.
What is the yield of this reaction?
CaCO 3 CaO + CO 2
Moles of CaCO 3 = 30/(40+12+16+16+16) = 30/100 = 0.3 mol
Moles of CaO = 0.3 mol
Mass of CaO = 0.3 x (40+16) = 0.3 x 56 = 16.8g
Masses of reagents Number of Moles = Mass
RFM
Volumes of Gases Number of Moles = Volume in dm3
24
e.g. Calculate the number of molecules in 18dm3 of carbon dioxide at r.t.p.
Number of Moles = 18 = 0.75 moles of CO2 molecules
24
Number of Molecules = 0.75 x 6.02x1023 = 4.52x1023 molecules of CO 2
3
Concentrations of Number of Moles = Concentration x Volume (in cm )
solutions 1000
write and interpret any balanced chemical equations required, including ionic equations
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 .
For example: CuSO 4(aq) + 2NaOH
(aq) Cu(OH) 2(s) + NaSO
4(aq)
The ionic equation is: Cu2+ (aq) + OH (aq) Cu(OH) 2(s)
(b) recall and explain the procedure for carrying out an acidalkali titration and be able to work out the results
Titrations allow you to find out exactly how much acid is needed to neutralise a quantity of alkali.
1. Measure out a fixed volume of alkali using a pipette and put it in a flask
2. Add a few drops of a suitable indicator e.g. phenolphthalein
phenolphthalein pink to colourless
methyl orange yellow to red
3. Fill the burette with acid
3. Do a rough titration add the acid to the alkali using a burette swirling regularly to find the end point, recording
the start and end point
4. Do an accurate titration run the acid in to within 2cm3 of the end point, then add the acid dropwise swirling
regularly, recording the start and end point then calculate how much acid is needed to neutralise the alkali
5. Repeat the accurate titration until you get concordant values

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Chemistry of Natural Resources: Elements from the Sea
Atomic Structure
(c) use conventions for representing the distribution of electrons in atomic orbitals (no treatment of the shapes
of atomic orbitals is expected)
Shells are labelled by giving each a principle quantum number, n. The higher the
value of n, the further the shell is from the nucleus and the higher the energy
associated with the shell. Each shell has a limit to the number of electrons is
called a filled shell.…read more

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Chemistry of Natural Resources: Elements from the Sea
Bonding and Structure
(e) draw and interpret 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;
What happens to electrons Atoms involved 'Dotandcross' diagram
Ionic Gains or loses electrons Between metal
Bondin Lose electron (metal) = and non metals
g positive ion
Gain electron (nonmetal) =
negative ion
Covalen Electrons are shared Between non
t metals
Bondin
g
Dative…read more

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Chemistry of Natural Resources: Elements from the Sea
use the electron pair repulsion principle to predict and explain the shapes of simple molecules (such as CH4,
NH3, H2O and SF6) and ions (such as NH4+) with up to six outer pairs of electrons (any combination of bonding
pairs and lone pairs) (no treatment of hybridisation or molecular orbitals is expected);
Electrons are all negatively charged so electron pairs will repel each other to the maximum degree of separation
and to minimum repulsion .…read more

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Chemistry of Natural Resources: Elements from the Sea
(g)explain, give examples of, and recognise in given examples the following types of intermolecular bonds:
Instantaneous dipole Electron movements in a molecule causes an uneven distribution of charge, forming
induced dipole an instantaneous dipole. The instantaneous dipole gets close to a neighbouring
(including dependence molecule, inducing a dipole in that molecule and becomes attracted to it.…read more

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Chemistry of Natural Resources: Elements from the Sea
(j) describe redox reactions of s and p block elements and their compounds in terms of electron transfer, using
halfequations to represent the oxidation and reduction reactions, and defining oxidation and reduction as loss
and gain of electrons
Example: Magnesium reacts with dilute hydrochloric acid
Mg(s)
+ 2HCl(aq)
MgCl2(aq)
+ H2(g)
Magnesium is oxidised : Mg(s) Mg2+ (aq) + 2e
+
Hydrogen ions are reduced : 2H (aq) + 2e
H2(g)
As the hydrogen ions oxidise the…read more

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Chemistry of Natural Resources: Elements from the Sea
The first ionisation enthalpy is the energy required to remove one electron: X (g) > X+ (g)+ e
The ionisation enthalpy INCREASES across a period as more protons are added to the nucleus so the attraction on
the outer electronsincreases making it harder to remove an electron because shielding stays the same across the
period.…read more

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Chemistry of Natural Resources: Elements from the Sea
Location Ideally the chemical plant should be:
Near the source of raw materials to reduce transport costs
Near existing works to provide skilled labour
Near good communication links to reduce transport costs
Near the customers to reduce deliverycosts
Near large amounts of water for cooling
Cost of Raw Materials the starting point for any chemical process
process Feedstock the reactants that go into a chemical process
and raw
materials The profit generated is the difference between the…read more

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Chemistry of Natural Resources: Elements from the Sea
If you shake the reaction mixture with an organic solvent like hexane, the halogen that's present will dissolve
readily in the organic solvent, which settles out as a distinct later above the aqueous solution.…read more

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