Consolidation Flashcards
(32 cards)
why atomic radius for TM almost constant?
- protons no. increases, nuclear charge increases.
- Shielding effect increases because the additional electrons are added to the inner 3d subshell.
- increase in shielding effect cancels out the effect of the increase in nuclear charge.
- effective nuclear charge and attraction for valence electrons remains fairly constant.
What is transition element?
It is a d-block element with partially filled d subshells which forms one or more stable ions
TM higher BPMP than s block elements
- 3d, 4d e- close in energy
- both 3d, 4d avaliable for delocalisation into sea of e-
- ↑ delocalised e- & ↑ charge density metallic bond stronger
TM why have variable oxidation state?
highest possible oxidation state = unpaired 3d + 4s e-
- both 3d & 4s e- similiar in energy,
- both 3d , 4s orbitals avaliable for for bond formation
Why are TM heterogeneous catalysts?
heterogeneous catalysts: catalyst and reactants different phases
- partially filled 3d subshell allows the exchange of e- to and from the reactant molecules
- facilitate formation of weak bonds with reactant molecules
what are ligands?
Ligands acct as Lewis Bases ( e- pair donor) and bond to Lewis Acid
- ion or molecule containing at least one atom that has lone pair of e-
- to be donated into a low-lying vacant orbital of metal atom or ion
- forming a dative covalent bond
- and forming a complex
Why are TM homogenous catalaysts?
- can exist in differnet oxidation states
- convert from one oxidation state to another
- due to the similar energy of the 3d and 4s orbitals
- this facilitates formation & decomposition of intermediates
what are complexes?
central metal ion linked to one or more ligands by dative covalent bonds.
why do TM form complexes?
- have **low lying vacant orbitals ** to accommodate lone pair of e- from ligands to form dative covalent bonds (DCB)
- small ionic radius and high charge density, → high polarising power and able to attract lone pair of e- from ligand to form DCB.
why are TM compounds coloured?
VERY SIGMA IMPTTT
- in pesence of water ligands, partially filled 3d orbitals of TM split into 2 groups of different energy levels
- e- that have lower energy d orbitals promoted to higher energy d orbitals as they adsorb energy from wavelength of visible light
- colour observed is complementary to the wavelength of light absorbed
Balance redox rxn
- balance O2 by adding H2O
- balance H2 by adding H+
- balance charge by adding e-
Purpose of salt bridge in electrolysis
- maintain electrical neutrality of each half cell
- complete the circuit allowing ions to flow without mixing electrolytes
limitations of Standard Cell Potential (E°cell) to predict spontaneity
- kinetic factor not considered as E° cell measure POE, rxn thermodynamically feasible but not kinetically feasible
- Rxn take place under non-standard conditions
- side rxn can still occur
Mode of action of heterogeneous catalyst
SUPA DUPA IMPT
- reactants adsorbed onto the active sites of the catalyst surface by forming weak interactions with catalyst
- This increases the surface concentration reactant on catalyst
- Adjacent (different) reactant molecules are brought close tgt and correct orientation
- This weakens the Intramolecular covalent bonds in the reactants resulting in lower activation energy than the uncatalysed reaction.
- Products formed diffuse from the catalyst surface, vacant active sites regenerated for adsorbing other reactants
Explain, with Boltzmann distribution, how the rate and rate constant is increased by a catalyst.
- Catalyst provides an alternative reaction pathway which of lowered activation energy.
- Thus, particles with energy equal to or greater than the actvation energy of the catalysed reaction E a(cat) increases or deduce from legend.
- This results in an increase in frequency of effective collisions,
- This results in a larger rate constant, k hence the reaction rate increases.
explain the trend in decomposition temperature from CaCO3 to BaCO3.
MUST QUOTE FROM DATA BOOKLET!!!!!
Down Group 2 from Ca to Ba, Ionic radii:
Ca2+ : 0.099nm Sr2+ : 0.113nm Ba2+ : 0.135nm
- charges stay the same but the ionic radii of the Group 2 cations, M2+ increases from Ca to Ba.
- As charge density = charge x radius , there is a decrease in the charge density of the Group 2 cations. Hence, the polarising power of the Group 2 cations decreases
- This results in the electron cloud of the large CO 3 2 – anion to be distorted (or polarised) to a smaller extent and a smaller weakening effect on the CO bonds within the CO 3 2 – by the M2+ .
- As more energy is required for decomposition (breaking down of the anion), the decomposition temperature increases from CaCO 3 to BaCO3 .
bond strength from SP3 to SP hybridisation
bond strength increases:
* s-chracter of the hybrid orbital increases
* hybrid orbital is less diffused,
* e- more tightly held by the nuclei —>
1) (link to basicity) e- less available for dative bonding with H+ and is a weaker base
OR
2) (normal elab) e- overlap with the orbital of another atom more effective, bond is stronger and bond length is shorter
state and explain the difference in bond angles using VSEPR.
- e- pairs arranged as far apart to minimise e- repulsion
- lp-lp repulsion > lp-bp > bp-bp > lone e- -bp
- increase in repulsion, bond angle decreases
why is Al2O3 an amphoteric oxide?
Al 3+ has high charge density/polarizing power which is able to polarise the electron cloud of O2− /anion , hence giving the oxide some covalent character.
Therefore, Al2O3 has a giant ionic lattice structure with covalent character, making it an amphoteric oxide that reacts with both acids and alkalis.
state the reactivity of oxides to acid/bases.
MgO is an ionic oxide. Hence it is basic and is able to react with acids.
MgO + 2HCl → MgCl 2+ H2O
SO 3 is a covalent oxide, hence it is acidic and is able to react with bases.
SO3 + 2NaOH → Na2SO 4+ H2O
Al2 O3 : amphoteric oxide hence it react with both acids and bases.
Al2O3 + 6HCl → 2AlCl 3+ 3H2O
Al2O3 + 2NaOH + 3H2O → 2Na[Al(OH)4]
is lattice energy of CaCl2 more or less exothermic than that of NaCl?
quote values from DATA BOOKLET!!!
Ca 2+ (r + = 0.099 nm) is bigger than Na + (r + = 0.095 nm).
But CaCl 2 comprises doubly-charged Ca 2+ whilst NaCl comprises singlycharged Na+ .
Since ionic charge is the **predominant factor **in affecting magnitude of lattice energy, the lattice energy of CaCl 2 is more exothermic than that of NaCl.
lattice energy is the energy evolved (exothermic)
formation of a dative bond
one atom must have lone pair of e- to be donated
another atom must have vacant, low-lying orbital to accept the pair of e-
what is SP hybridisation?
from sp3 to sp, decrease in p orbitals that mix with 2s orbitals
sp hybridisation results when one 2s and one 2p orbital of C mix to form two sp hybrid orbitals. There are two unhybridised p-orbitals in C. (unhybridised p orbital forms the pi bond)
make sense there is 2 unhybridised as there are c triple bonds in SP
why entropy increases when temp increase
there is a increase in disorder of the system:
* temp ↑, KE ↑
* broadening of the energy distribution of the particles
* more possible energy states particles can adopt at higher temperature
* increase in entropy
