Elements From The Sea Flashcards
Fluorine risks and benefits
Benefits- used to make plastics PTFE
Added to toothpaste to strengthen enamel
Used to make HFCs
Risks- highly reactive and handling must be kept to a minimum
Chlorine risks and benefits
Benefits- used in plastic industry (PVC)
Used in water treatment and to make pesticides, medicines and bleach.
Important intermediate in manufacture of HCl and chlorinated solvents
Risks- pesticides can accumulate in environment
CFCs destroy stratospheric ozone
Risks and benefits to bromine
Benefits - manufacture of flame retardants, agricultural figments and photography
Risks- organic bromine compounds can destroy ozone in stratosphere
Iodine benefits
Used in antiseptics, germicides and dyes
Iodine-131 is use to diagnose thyroid disease
Structure of ionic lattice (NaCl)
Na surrounded by 6 Cl
Simple cubic
Water in ionic lattice - water of crystallization
Crystals said to be hydrated
Ionic substances in solution
Hydrated ions are randomly arranged and behave independently
Each ion is surrounded by water molecules - known as hydration
-/+ have different shapes as H2O is bent
Spectator ions
Not involved in reaction and not in ionic equation
Rules to help tell if ionic precipitation reactions will take place when two solutions are mixed
- all nitrates are soluble in water
- all chloride are soluble in water except AgCl and PbCl2
- all sulfates are soluble except BaSO4, PbSO4 & SrSO4
- all sodium, potasium and ammonium salts are soluble
- all carbonates are insoluble except (NH4)2CO3 and those of the group 1 elements
First ionization enthrall definition
Energy needed to remove one electron from each of one mole of isolated gaseous atoms of an element.
One mole of gaseous ions with one positive charge is formed.
Oxidation state of F and O
O= -2 F = -1
Oxyanions what are they
Negative ions that contain Oxygen and another element. Names end in -ate ie chlorate
Displacement reaction
More reactive halogen is passed into a solution of less reactive halogen.
Group 7 elements
Halogens
Fluorine physical properties
At rt - pale yellow gas
Volatility- gas
Solubility in water- reacts with water
Solubility in organic solvents- soluble
Chlorine physical properties
At rt - green gas
Volatility - gas
Solubility in water - slightly soluble to give pale green solution
Solubility in organic solvents - soluble to give pale green solution
Bromine physical properties
At Rt - dark red liquid
Volatility - liquid quickly forms brown gas on warming
Solubility in water - slightly soluble to give red-brown solution
Solubility in organic solvent - soluble to give red solution
Iodine physical properties
At rt - shiny black solid
Volatility - sublimes on warming to give purple vapor
Solubility in water - barely soluble gives brown solution
Solubility in organic solvent - soluble to give violet solution
All halogen properties
Diatomic molecules (F2)
Intramolecular bonds - covalent
Intermolecular - I’d-I’d.
Halogens oxidizing agents / reducing agents?
Oxidizing,, tend to remove electrons from other elements
Reactions with silver ions and halide ions
Fluorine - none
Chlorine - white silver chloride
Bromine - cream silver bromide
Iodine - yellow silver iodide
Anode and cathode
Anode =+
Cathode -
Anion & Cation
Anion -
Cation +
Storage and transport of fluorine
Fluorine is very reactive, too reactive to store. Made in situ when needed by electrolysing liquid hydrogen fluoride.
Difference between being polar and being polarized
Polar - permanent dipole
Polarized - dipole
Id- id
Electron density unevenly distributed at any one time -instantaneous dipole. Movement of electron cloud.
If another molecule is close it can become induced as its electron cloud is attracted to the positive end of the other electron cloud. = induced dipole.
Pd-pd
Difference in electronegativity
Electronegativity definition
Degree to which an atom of an element attracts electrons.
F> O> Cl> Br
N> I> S> C > H
Homolytic fission of halogenoalkanes
Comditions - uv radiation
Or gas phase with high temp
RADICALS
Heterolytic fission with halogenoalkanes
Conditions - dissolved in a polar solvent such as ethanol/water mixture
R-Hal —> R+ and Hal-
Forms carbocation
Substitution reactions with halogenoalkanes
Nucleophilic substitutions. C-Hal bond breaks and is replaces by X-
nucelophile defintnion
One or more lone pairs of electrons they can donate to form new bonds
Halogenoalkanes to alcohol
H2O
Heat under reflux (hydrolysis)
Or with OH-
Heat under reflux with NaOH with ethanol as solvent
Halogenoalkanes to amine
Ammonia (NH3)
Heated with conc. ammonia solution in a sealed tube
Preparation of halogenoalkanes
Chloroalkane is immiscible in water. Forms later above aqueous products. Separating funnel.
Upper layer containing chloroalkane is run of into clean beaker
Shaken with sodium hydrgoencarbonate remove acidic impurities
Chloroalkane layer ran off again
Anhydrous sodium sulfate is added to remove water
Chloroalkane purified by distillation
Batch and continuous process
Batch - placed in vessel and react. Once over, taken out machine cleaned and made ready for next batch.
Continuous - starting material regularly fed into one end of plant and product emerges at other.
KNOW ADV AND DISASDV OF BOTH
Raw materials — >
Feedstock (reactants)
Co-products
Produced at same time as the desired products via the same reaction
By- products
Result from unwanted side reactions
Percentage yield -
(Actual mass of product / theoretical max mass of product ) x 100
Atom economy -
(Relative mass of useful product/ mass of reactants used) X 100
