Salters Chemistry, Elements of the Sea notes

My notes on Elements of the sea for the Salters F332 (unit 2) exam

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Elements of the Sea
Ionic equations
o If 2 solutions react to form a solid, a precipitation
reaction occurs. Eg. Ag+(aq) + No3-(aq) + Na+(aq) +
Br-(aq) goes to AgBr(s) + Na+9aq0 + NO3-(aq)
Then cancel spectators
Ag+(aq) + Br-(aq) goes to AgBr(s)
o Always include state symbols
o Only split into ions if aqueous and ionic
Ionic solids
o Cations and anions are held together by strong
electrostatic attractions in a giant
ionic lattice.
o Each sodium ion is surrounded by
6 chloride ions 6:6 coordination.
It is a simple cubic structure.
o Ionic solids are hard and have a
high melting point due to strong
electrostatic attractions between
o If ionic crystals contain water, the
water molecules fit into the lattice the same way as
regular ions. This is called the water of crystallisation.
These crystals are said to be hydrated.
o If these hydrated crystals are heated, the water
molecules are driven off and you are left with an
anhydrous solid.
Ionic substances in solution
o As ionic substances dissolve in water, the ions become
surrounded by water molecules and they spread
throughout the solution. The hydrated ions are randomly
arranged and behave independently.

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Water surrounds the ions in this way because it is polar
and bent. The partially + H ions are attracted to the
partially negative ions.
o In positive ions, the water molecules surround the ion
with the oxygen atoms pointing inwards, and with the
hydrogen atoms pointing inwards in negatively charged
Rules on solubility
Soluble salts Insoluble salts
All sodium, potassium and All carbonates are insoluble
ammonium salts. except for sodium, potassium
and ammonium carbonates.…read more

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First ionisation enthalpy
o The energy needed to remove one electron from every
atom in a mole of gaseous atoms.
o One mole of gaseous ions with one positive charge is
X(g) goes to X+(g) + e-
o Units are kJmol-1 and FIE is always positive as energy
must be put in to remove the electron as it is attracted to
the positive nucleus.
o The peaks are elements in
group 0 (noble gases).…read more

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Oxidation is losing (electrons) reduction is gaining (electrons).
Oxidation is an increase in oxidation states
Reduction is a decrease in oxidation states
Oxidising agents are reduced (decrease in oxidation states)
Reducing agents are oxidised (increase in oxidation states)
o `Oxyanions' are negative ions that contain oxygen and
another element. Their names end in `ate' eg.sulfate.
They should include an oxidation state in their name.…read more

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The Halogens
Physical properties
Flourine: Pale yellow gas, reacts with water, soluble in
organic solvents.
Chlorine: Pale green gas, slightly soluble in water and organic
solvents to give a pale green solution. Forms a white
precipitate of silver chloride with silver ions.
Bromine: dark red liquid, forms a brown gas on warming.
Soluble in water and organic solvents to give red-brown and
red solutions respectively. Forms a cream precipitate of
silver bromide with silver ions.…read more

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Transport routes
avoid residential areas and it is often transported at
Elements are split into number shells 1-4, these are split up
into sub-shells, s, p, d and f.
S sub-shells have 1 orbital and can hold 2 electrons
P sub-shells have 3 orbitals and can hold 6 electrons
D sub-shells have 5 orbitals and can hold 10 electrons.
o Orbitals fill with one electron in each before going back
and putting 2 electrons in each orbital.…read more

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If the last electron in the element entered the s sub shell, it is
said to be in the `s-block' of the periodic table. This is also true
of the other 3 blocks, p, d and f.
Extracting Bromine from sea water
o Partially evaporated, acidified sea water is warmed and
chlorine is added. It needs to be acidified as sea water is
naturally slightly alkaline and both chlorine and bromine
dissolve in alkali.
o Steam is blown through the product.…read more

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o Cost effective for small quantities
o Slow reactions are catered for
o A range of products can be made in the same vessel
o A greater % conversion for the same amount in the same
time than with continuous
o Charging and emptying the vessel is time consuming as
is hut down time.
o Larger workforce needed than continuous
o Contamination is more likely as the same vessel is used
for different reactions.…read more

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Green Chemistry aims to reduce the use of feedstocks to a
minimum eg. Recycle unused reactants and solvents and
increase atom economy.
Reduce energy consumption eg. Use enzymes to reduce
temperature needed or keep no. of steps to a minimum.
Minimise waste ­ recycle or find ways to make use of waste
Co-products are produced at the same time as the desired
product via the same reaction. As the amount of desired
product increases, so does the amount of co-products.…read more

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The membrane is made from the PTFE polymer and has
negatively charged side chains which the Na+ ions are
attracted to. These side chains repel Cl- and OH- ions. Some
water molecules are attached to the sodium ions and pass
through but the membrane is impermeable to free water
molecules.…read more




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