Steel Story Flashcards
Extracting and purifying metals: where they found and how they extracted
Found as compounds in earths crust
Extracted by reduction method depends on reactivity of the metal
How are reactive metals extracted
Eg of reactive ie group 1&2 &aluminum extracted by electrolysis
Less reactive metals obtained from their ores by
Eg iron and zinc
And reduction with carbon and carbon monoxide
Unreactive metals how they extracted?
Eg gold and silver
Found as elements in the earths crust
3 ways to prevent corrosion against metal
Barrier protection- prevents oxygen coming into contact with iron/steel. Eg: painting, greasing, oiling and using polymer coatings
Galvanizing- steel can pin be covered in thin layer of protective zinc that oxidizes. Stainless steel contains chromium that oxidizes, leaving protective oxide layer.
Sacrificial protection: attaching blocks of more reactive metal (ie zinc) to large iron structures (ships) electrochemical cell is formed and the reactive metal corrodes preferentially.
Where are transition metals found in periodic table
D block
transition metal definition
D-block element that forms at least one ion with a partially filled sub-shell of d electrons.
D-block elements react to form ions what are first to be lost
4S electrons
Two exceptions to transition metals and why (elements)
Scandium - Sc3+ = 3d0
Zinc - Zn2+ = 3d10
Ions form empty or full d orbitals
D - block metals physical properties
Good conductors of heat and electricity
Denser than S and have higher melting and boiling points
Hard and durable with high tensile strength and good mechanical properties
Transition metals chemical properties: (4)
Variable oxi states
Formation of colored ions
Formation of complexes
Catalytic activity
Variable oxidation states for transition metals- why and how
Because succession ionization enthalpies in 3D and 4S sub-shells are so small , so multiple electron loss is possible. In lower oxidation states - simple ions
In higher oxi states - they’re covalently bonded to electronegative element ie O and F forming anions
Redox reaction transition metals and oxi states. Oxidisng agent or reducing agents
High oxi state - oxidizing agents
Low oxi state - reducing agents
Formation of colored ions transition metals
Cu2+ Fe2+ and Fe3+ colors
Electron transitions occur within 3d sub-she’ll when vi visible light is absorbed. - only for ions with partially full d shells
Cu2+ (Aq) blue
Fe2+ (Aq) green
Fe3+ (Aq) yellow/orange
Transition metals as catalyst
Heterogenous- provide surface for gaseous reactant to be adsorbed onto. Weak interactions between 3d and 4s electrons of transition metal keeps the molecules in place.
Homogenous - they’re able to change from one oxidation state to another during the reaction before turning back to their original
Ligand definition
Molecules or anions with one or more lone pairs of electron
In a complex…
A central metal ion is surrounded by Ligands
What type of bonds to Ligands form with the metal
Dative covalent
Number of bonds between central metal and Ligands is called
Coordination number
Complex with overall charge
Complex ion, add square brackets and charge outside bracket
Shapes of complexes coordination numbers 6 4 &2
6 octahedral
4 tetrahedral can be square planar
2 linear
Single edta4- can form _______complex by _______ this is known as ______
Hexadentate
By wrapping itself round central metal atom
Known as chelation
Types of Ligands
One bond to central
2 bonds to central
Many bonds to central
1- monodentate
2- bidentate
Many - poly dentists
Naming complexes
Write the number of each type of ligand using, mono, di, tri, tetra, penta, hexa
Writhe the name of each ligand in alphabetical order
Write the name of central metal - English name if + or neutral and latinised name if negative
Write oxidation number of central metal in brackets
Latinised names of metals
Cu cuprate V vanadate Ti titanate Ag argentate Zn zincate Pb plumbate Cr chromate
Color in complexes
Lights falls on a complex some is absorbed some reflected/ transmitted.
Visible light is absorbed complex appears colored.
Presence of Ligands causes 5 d orbitals of central metal to split. Some become slightly higher in energy some lower. The small gap between these allows visible light to be absorbed. The colour of the complex we see is the complementary colour to what’s absorbed.
Ligand substitution reactions
Also known as Ligand exchange reactions
One ligand displaces another. Occurs if new complex formed is more stable than the previous complex.
Precip reactions with cu2+ fe2+ and fe3+
With sodium hydroxide
Fe2+ = green gelatinous solid
Fe3+ = orange gelatinous solid
Cu2+ = light blue solid
Ammonia solution added to a solution containing copper (II) ions
Dark blue/violet solution forms
Ligand substitution example
Larger the Kstab
Stability constant the more stable a complex is
Potassium manganite (VII) titration
Pm = strong oxidizing agent used for solutions containing iron(II) or hydrogen peroxide.
Method-
Use Pipette to add a known volume of test solution into conical flask
Acidity this solution with dilute sulfuric acid
Add form burette pm and swirl till pale pink persists
Repeat titration till you have two titles within 0.1cm3 of each other
Iodine- thiosulfate titration a
Used to find concentrations of oxidizing agents.
Known amount of oxidisng agent reacts with an excess of acidified potassium iodide solution. Iodine produced is then titration against a standard solution of sodium thiosulfate. Near end point few drops of starch solution is added giving intense blue/black colour, this disappears at the end point.
Electrode potentials why and what
Metal is places in Aq solutions of its ions equilibrium is established. An electrode potential is created between the metal and the solution of ions.
More negative electrode means
Greater the tendency that the metal will release electrons and for ions. Altering temp or concentration of ions in solution alters the value of electrode potential
Two half cells connected together =
Electrochemical cell
Potential difference between two half cells =
Cell potential or e.m.f
Ecell
In a half cell which has negative terminal
One with more negative electrode potenatial
Electrons flow from
Negative terminal to positive terminal
Standard electrode potentials
Standard hydrogen half-cell, it’s electrode potential under standard conditions 0.00V
Half cell containing molecules and ion or ions an
Platinum electrode is used (inert electrode)
Standard conditions for standard electrode potentials
Temp 298 K
Pressure 1 ATM
conc 1mol/dm^3
E cell =
Most positive electrode - most negative elecrtrode
Predicting direction of a reaction
Remember half cell more negative electrode potential supplies electrons to half cell with more positive.
- Look up half reactions and standard electrode potentials
- Identify which half reaction has the more negative electrode, rewrite this showing it supplying electrons.
- Balance number of electrons and add them together
Rusting description
At the edges of water droplet, oxygen concentrations are higher, and oxygen is reduced to hydroxide ions. Away from edges iron atoms are oxidized to iron(II) Ions.
Two half reactions involved in initial stages of rusting are
Fe2+ (aq) + 2e- --> Fe(s) O2(g) + 2H2O (l) + 4e- --> 4OH- (aq) Rust forms in series of secondary reactions 1. Fe2 + 2OH- --> Fe(OH)2 (s) 2. Fe(OH)2 (s) --O2--> Fe2O3.xH2O(s)
Why recycle steel?
Saves resources and energy& helps to reduce waste. Is magnetic so can be easily separated from other waste. Except for aerosols all steel used for packaging is easily recycled. Scrap steel is important in the BOS process- it’s added to the converter before the molten iron is poured in to help reduce ‘thermal shock’
Why does an object appear colored?
Visible light falls on an object some wavelengths are absorbed and some reflected/transmitted. We see reflected/transmitted wavelengths. If all visible light is transmitted it will appear colourless.
Electronic transitions - reasons for colour
When visible light falls on a colored substance the absorbed light is in the energy range that causes electronic transitions , electrons move to higher energy levels and the molecules become excited. Molecules. Don’t remain excited for long, as electrons fall back down intimidate energy levels the energy is re-emitted in various forms, including vibrational energy , many diffferent vibrational energy level within each electronic energy level.
Colorimetry what and why it’s used
Experimental technique used to find concentration is a colored solution. The amount of energy absorbed by a solution - its absorbance- its proportional to the conc of the solution
