s block Flashcards
What are the 2 ways to produce hydrogen and what are the equations involved?
- Steam reforming
CH4 + H2O (with 800 degrees and ni oxide) -> CO + 3H2
CO + H2O (200-450 degrees) Fe catalysts -> CO2 + H2
- Electrolysis of water
2H2O + 2H2 + O2
What are 3 uses of hydrogen?
- Production of ammonia
- Production of methanol and organic compounds
- Hydrogenation of unsaturated compounds
What are the 3 types of binary hydrogen compounds?
Covalent hydrides: H + p block elements
Saline hydrides: H + s block/electropositive elements
Metallic hydrides: H + d/f block elements
What are the 3 types of hydrogen atoms?
Protic hydrogen (H+)
Hydridic hydrogen (H-)
Radical hydrogen (H.)
what are the 2 things that relate to the strength of a bond?
- Orbital overlap
- Ionic contribution to the bond
what is a major factor to determine the strength of single and multiple bonds
single bonds: electronegativity
multiple bonds: orbital overlap
what are the different types of ores?
oxides, sulfides, carbonates, native, noble, silicates
what is the ionization energy equation?
IE = -Eorb x (Zeff/n)^2
what is the equation to find the %of ionic bonding?
% = (Q / charge of an electrons) x 100
what is the trend between orbital size and strength of bond?
larger orbital size -> more diffuse -> poorer overlap -> weaker bond -> more reactive
when is the oxidation state of an element 0?
single atom, lattice, or moleculear form (eg. O2)
what determines the charge on hydrogen?
the electronegativity of the element compared to hydrogen
what is currently a developing use of hydrides?
storage for hydrogen (NaBH4 with water to form hydrogen gas) to be used in fuel cells
what is the packing for all G1 metals?
BCC
how is each G1 element produced?
Li and Na through electrolysis of molten chlorides (down cells)
K, Rb, Cs through reduction of its chloride with Na
what are some uses of G1 elements?
Li -> solid state batteries (small = greater mobility)
Na: NaOH (industrial chemical) + NaCl (table salt and road clearing)
what compounds do G1 elements form and what are their equations?
hydrides, hydroxides, oxides, carbonates and halides
what are the 3 types of oxide ions?
oxide (O2-)
peroxide (O2 2-)
superoxide (O2 -)
which oxide can be reacted with carbon dioxide to produce oxygen for breathing apparatus?
KO2
what is the solubility of G1 salts dependent on?
large anion: solubility decreases down the group as larger ion means lower nuclear charge thus lower attraction to the solvent/water molecules
small anion: solubility increases down the group as the cation can be easily solvated and the bond between the cation and anion is weaker down the group due to poor orbital overlap thus more likely to be separated (soluble)
how can the solubility of G1 elements be improved?
wrapping up the metal ions in macrocyclic crown ether ligands
what are the irregularities of melting points in G2 elements?
caused by different packing structures (CCP is closer together than HCP thus sudden higher melting point of calcium)
how are G2 elements produced?
Mg is the only element in G2 that is massed produced and it is done through the thermal decomposition of metal carbonates
Eg. from dolomite (MgCO3 . CaCO3)
-> lose CO2 first then react with Si to form Mg on its own
what are some uses of G2 elements?
Be (high thermal conductivity, not magnetic): aerospace and alloying
Mg: aluminium alloys (increase resistance to corrosion and greater mechanical strength)
what compounds do G2 elements form?
which elements do not form oxides and hydroxides and why?
oxides, halides, sulfides, nitrides and hydroxides
Be and Mg do not form hydroxides and oxides because they have a protective oxide layer that makes the metal kinetically inert
why is Be different from the other elements in its group?
due to its high polarising power it can withstand the power of anions thus results in polar covalent compounds rather than ionic compounds
what is the unique property of BeCl2?
in gas Be is linear
in solid state it forms chains due to donation of electron density from chlorine into electron deficient Be (not possible unless covalent as ionic is full separation of charge)
