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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…

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o 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…

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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

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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.…

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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…

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lead-lined steel tanks in metal frames. 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…

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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…

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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…

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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…

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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




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