Inorganic (Hanno) Flashcards
Define Bronsted acid and Bronsted base
Bronsted acid - proton donor
Bronsted base - proton acceptor
Define Lewis acid and lewis base
lewis acid - electron pair acceptor
lewis base - electron pair donor
What is the conjugate base of nitric acid HNO3?
NO3-
Define ionizable proton
available protons
How many ionisable protons does nitric acid have?
1
What is the conjugate base of sulfuric acid H2SO4?
HSO4-
How many ionisable protons does sulfuric acid have?
2
what is the conjugate base of phosphonic acid H3PO3
H2PO3-
How many ionisable protons does phosphonic acid have?
2
What is the conjugate base of phosphoric acid H3PO4
H2PO4-
How many ionisable protons does phosphoric acid have?
3
How do we measure how strong acids are?
measured by the value of PKa which is the acid dissociation constant, the lower the PKa the higher the Ka so the more acidic, stronger acid
What is the trend in acidity going down a group and why?
stronger acid
because there is a weaker orbital overlap, Decreasing H-X bond energy so therefore easier dissociation. Lower Pka down a group so lower Ph so stronger acid
what affect does a greater degree of ionisation have on the property of an acid and why?
weaker acid, Increasing difficulty of
removing H+ from anion, acidity decreases with a higher build up of charge
what is an oxo group
where ther is an OH and a double bond to oxygen on the same central atom
what is paulings rule equation for predicting experimental pKa
8-5(p)
where p is the number of oxo groups
how does more oxo groups affect acidity
more oxo groups means a stronger acid as there is a greater delocalisation and a greater stability of the conjugate base due to resonance structures
how does paulings rule work for polyprotic acids
pKa = 8-5p + 5
For polyprotic acids pKa
increases by 5 units [each time
why are are acids weaker in aprotic solvents
In aprotic solvents for example acetonitrile acids are much weaker as there is a problem solvating anions in non-protic solvents making it harder for the acid to donate protons.
what is the difference between solvation of ions in protic and aprotic solvents
in protic solvents - solvation of anions stabilises H= o therefore hydrogen bonding can occur
in aprotic solvents - no solvation of anions so therefore no hydrogen bonds
what Pka for compounds are quoted in water
-1.7 to 16
what Pka for compounds are alternative solvents used and give examples of alternative solvents
above 16
acetonitrile pka 25
dimethylsulfoxide pka 35
define acid
electron deficient
acids are coordinatively unsaturated whereas bases have excess electrons in the form of a lone pair or anionic charge
define base
electron rich
which is the lewis acid and which is the lewis base the metal or the ligand
lewis base - ligand and an electron pair acceptor
lewis acid - metal and an electron pair acceptor
what is an aqua acid
water ligand, making water acidic by adding a metal
what does acidity depend on
oxidation state and ionic radius, governed by electrostatic interactions
properties of strong acids
small ion
high oxidation state
stable conjugate base
properties of weaker acids
large ion
low oxidation state
less stable conjugate base
are metal hydroxides considered to be acidic or basic
most metal hydroxides would be considered basic, much less acidic than aqua acids. deprotonated hydroxide needs to be stabilised. still acidic in aqueous media pka ~ 8 lower than water
what is magic acid
mixture of SbF5 + HF or HSO3F
what is aqua regia
HCl and HNO3
what is piranha solution
H2SO4 and H2O2
what is HSAB
Hard - soft acid- base principle (HSAB)
Cations (Lewis acids) and ligands (Lewis bases) classified as either HARD or SOFT
Hard acids prefer hard bases
Soft acids prefer soft bases
features of hard acid and bases
small ionic radius
high os
low polarizability
high electronegativity
high bonding orbital energy
ionic bonding
features of soft acids and bases
large ionic radius
low OS
high polarizability
low electronegativity
low ion solvation
low bonding orbital energy
covalent bonding
what are the types of bonds between hard/hard and soft/soft acid and bases
Bonds between hard lewis acids and bases tend to be ionic ( attraction forces between + and -)
Bonds between soft lewis acids and bases tend to be covalent (frontier molecular orbitals)
give examples of hard acids
H+
Li+, Na+, K+
Be2+, Mg2+, Ca2+
Al3+, Ga3+, ln3+, BF3, BCl3, B(OR)3, AlMe3
La3+, Th4+
Sc3+, Ti4+, Cr3+, Fe3+, Co3+
trend down a group with HSAB
down a group metals get softer
are higher oxidation states usually harder or softer
harder
give examples of borderline lewis acids
group 7
BBr3
In+
Sn 2+ Pb 2+
Fe 2+, Co 2+, Ni 2+, Cu 2+, Zn 2+
give examples of soft lewis acids
Tl+, Cs+, Cu+
Cd 2+, Hg 2+, Ag+, Au+, Pd 2+, Pt 2+
BH3
give examples of hard lewis bases
R3N amines
H2O, R2O ethers, RO-
F- Cl-
conjugate bases of oxoacids
RCOO-
SO4 2-
CO3 2-
NO3 -
PO4 3-
give examples of borderline lewis bases
NO2-, N2, N3-
SCN-
pyridine
SO3 2-
BR
give examples of soft lewis bases
heavier elements
R3P, (RO)3P
RSH, R2S, RS-, SCN
I-
CO, C2H4, C6H6, Cn
H-
define conjugate acid
what remains after an acid has donated a proton during a chemical reaction
define conjugate base
the species formed after donating an H+ from an acid
draw the structure of HNO3
google this
draw the structure of H2SO4
draw the structure of H3PO3
draw the structure of H3PO4
how do we calculate the position of equilibrium for protolytic equilibrium
K= 10 to the power of - Ka of HY/ 10 to the power of -Ka of the HX
what is the trend of acidity going along a period and why?
going along a period thw acid becomes stronger. the electronegativity increases and the molecule will get more polar which makes it easier to break the H-X bond producing a stable ion. Pka decreases along the period meaning lower PH more acidic
Explain why the Lewis acidity of the silicon tetrahalides follows the trend SiI4 < SiBr4 < SiCl4
< SiF4
inductive effect - decreasing lewis acidity from SiF3 to SiI3. decreasing electronegativity with F being the most electronegative. these electronegative atoms will withdraw electron density away from the Si, so the more electron density withdrawn the more electron deficient the Si centre
explain why the boron trihalides it follows the trend BF3 < BCl3 < BBr3 < BI3
mesomeric effect - increasing lewis acidity from BF3 to BI3. F is a small ligand, increasing ligans size. with smaller ligands there is better orbital overlap meaning there is a shorter B-X bond. energies of orbitals closer between B-F therefore less lewis acid, whereas I has weaker orbital overlap so a longer B-X bond so more lewis acidic
polymers from aqua acids
condensation reaction - removal of water
reaction formed under basic conditions
Describe the acidity of metal hydroxides/ hydroxo acids
most metal hydroxides would be considered basic, they are much less acidic than aqua acids, the deprotonated hydroxide needs to be stabilised, still acidic in aqueous media
what are oxo groups
M=O double bonds,
describe the trend in acidity between oxo acids, aqua acids and hydroxo acids
acidity
1) oxo acids
2) aqua acids
3) hydroxo acids
what is a metathesis reaction
double displacement - two complexes swapping partners
what is the irving-william series
stability of complexes containing M2+ following the order
M2+ = Ba<Sr<Ca<Mg<Mn<Fe<Co<Ni<Cu
binding of ligands to metal gets tighter feels more of effective nuclear charge
what does the irving - williams series tell us
for any ligand, the order of stability follows the irving william series. Metal ions ranked higher in the irving william series will displace another metal ion in a complex
describe hydrogen bonding in HSAB
H+ is a hard LA therefore it prefers to bind hard LB. Water(o) ammonia (N) and fluorine(F) are hard LB so hydrogen bonding is possible. Weak H-bonding for softer H-bond acceptors such as I
describe the Hard lewis acids and bases in naturally occurring ores and minerals
hard lewis acids Mg, Ti and Al
magnesia MgO
titania TiO2
alumina Al2O3
silica SiO2
describe the soft lewis acids and bases in naturally occurirng ores and minerals
soft lewis acid Ag, Pb and Hg
acanthite Ag2S
chaococite Cu2S
galena Pbs
cinnabar Hg|S
