chem ct Flashcards
charge density formula
|charge/mass|
isoelectronic
same total number of electrons
pv (y) p (x) graph
straight or horizontal
straight
pv constant
why do you not use direct titration for iodine
iodine is volatile, concentration varies throughout the course of titration
would enthalpy change of neutralisation changwith the number of moles?
no, even though twice amount go heat produced, twice the amount of water is also produced
define: relative isotopic mass
mass of 1 atom of isotope /
1/12 mass of 1 atom of carbon-12
define: relative atomic mass and relative molecular mass
(weighted) average mass of 1 atom/molecule of the element/substance /
1/12 x mass of 1 atom of carbon-12
avogadros hypothesis
equal volumes of gas under the same conditions of temperature and pressure contain the same number of molecules
define: disproportionate reaction
a redox reaction whereby the same element is a substance is simultaneously oxidised and reduced
shape of s, p and d orbitals
s - spherical shape
p - dumbbell shape
d - lobes
characteristics of s and p orbitals
s non-directional
p directional
as n increases, s and p are more diffuse
(2p<3p<4p<5p)
anomalous electronic configurations
cr and cu
cr: 3d5, 4s1
3d and 4s orbitals are about the same energy by the time cr is reached
having one electron each in 3d and 4s orbitals, inter-electronic repulsion is minimised
cu: 3d10, 4s1
fully filled 3d sub shell is unusually stable due to symmetrical charge distribution around the metal centre
3 criteria that affects electrostatic attraction between nucleus and electrons
- no of electronic shells
- nuclear charge
- shielding effect
2+3 effective nuclear charge
note: used to explain atomic radius, ionic radius, IE, electronegativity
large jump in between 1st and 2nd IE
large jump between 1st and 2nd IE, significantly more energy required to remove the 2nd electron as it is located in a different electronic shell, one that is inner and nearer to the nucleus, hence experiences a stronger electrostatic attraction to the nucleus and there is 1 valence electron
electronegativity
electronegativity relative measure of its ability to attract bonding electrons
affecting strength of metallic bond
- number of valence electrons
2.charge of cations - size of cations (charge density)
covalent bond
between a shared pair of electrons and positivity charged nuclei
why does pcl5 exist but not ncl5
period 3 elements like p have vacant low lying orbitals eg 3d orbitals available for the expansion of octet however period 2 elements can only accommodate a max of 8 valence electrons
dipole moments of polar and non-polar
polar got dipole
non-polar no dipole moments
how do id-id interactions arise
exist in non-polar molecules
electrons are constantly moving in any particle
at ay given moment, electron density of a particle can be unsymmetrical, resulting in an instantaneous dipole
factors affecting id-id interactions
- electron cloud size
> larger number of electrons, larger electron cloud, more easily polarised, stronger id-id bonds - surface area for molecular interaction
> straight-chained hydrocarbons greater surface area for intermolecular interactions compared to branched isomers, idid stronger in straight chains
how do pd-pd interactions arise
electrostatic attraction between s+ end of one molecule and s- end of the other molecule gives rise to pd-pd interactions
factors affecting strength of pd-pd interactions
more polar, stronger pd pd bonds
dipole moment of the molecule (electronegativity difference)
factors affecting strength of hydrogen bonds
extensiveness of hydrogen bonding
> number of bonds per molecule i.e.h2o 2h bonds per molecule
> to find no of bonds, find the lower number of no of lone pairs or no of H
strength of hydrogen bonding
larger dipole moment, F more electronegative than N
solubility in water
type of solute-solvent interaction
> favourable because solute-solvent interaction is id-id interactions which are similar to solute-solute and solvent-solvent interaction
> unfavourable because solute solvent interaction is id-id interactions which are weaker than hydrogen bonding in water
ionic solids tend to dissolve in water
> large amount of energy released from ions forming ion-dipole interactions with the polar water molecules can compensate for the energy required to overcome strong ionic bonds (depends on charge, size of ion, dipole moment and size of polar molecule)
chemical reaction occurs
reaction products form favourable interaction with solvent
solubility in water
type of solute-solvent interaction
> favourable because solute-solvent interaction is id-id interactions which are similar to solute-solute and solvent-solvent interaction
> unfavourable because solute solvent interaction is id-id interactions which are weaker than hydrogen bonding in water
ionic solids tend to dissolve in water
> large amount of energy released from ions forming ion-dipole interactions with the polar water molecules can compensate for the energy required in the formation of strong ion-dipole interactions (depends on charge, size of ion, dipole moment and size of polar molecule)
pi bonds vs sigma bonds
sigma bonds are when orbitals overlap head on
pi bonds are when they overlap side-to-side
covalent bond strength (4)
no of bonds between atoms (single double triple)
effectiveness of overlap (diffuse, less effective)
difference in electronegativities of the bonding atoms (more polar)
type of hybridisation of the orbitals of the bonding atoms
degree of covalent character
higher charge, smaller cation, stronger polarising power
electron clouds of anions larger, more easy to distort
ideal gas
particles of negligible volume
particles exert negligible attractive forces on one another
gases approaching ideality
low pressure, volume occupied by gas particles can be considered to have negligible volume compared to the volume of the container, intermolecular attractive forces between the widely spaced gas particles are negligible
high temperature, gas particles possess sufficiently high kinetic energy to overcome intermolecular attractive forces
spontaneous processs
once started, will continue without any external assistance
entropy
measure of disorder of matter and energy in a system, the more disordered, the larger the entropy
disruption of crystals increases entropy
hydration decreases entropy
Gibbs free energy change
predict whether the process or reaction is spontaneous
exergonic endergonic
