som week 7 Flashcards
give equation for dipole moment and the units of each value
μ = Qr
μ - coulomb metres, Cm or debyes, D, conversion is given in data table
Q - coulombs, C
r - distance in metres between the two charges, m
give the equation for the addition of two dipole moments
μ = √(μ₁² + μ₂² + 2μ₁μ₂cosθ)
basically cos rule
give the equation for the 𝑥, 𝑦 and 𝑧 components of a dipole
how is the overall dipole calculated from these components?
μ𝑥 = ΣQj 𝑥j μ𝑦 = ΣQj 𝑦j μ𝑧 = ΣQj 𝑧j
j meaning of each atom
Qj = charge of each atom in the molecule
𝑥j = 𝑥 of each atom in the molecule
so it is the sum of the each atom’s charge x position
overall μ = √(μ𝑥² + μ𝑦² + μ𝑧²)
what symbol is used for an induced dipole?
what is an induced dipole proportional to and what two equations are derived from this?
μ*
μ* ∝ size of electric field, E
μ* = ɑE
μ* = 4πℇ₀ɑ’E
4πℇ₀ = scaling constant, ℇ₀ is vacuum permittivity which is given
ɑ and ɑ’ = polarisability and in the last equation the units are m³
E = electric field, V/m
give the equation for the interaction between two charges in a vacuum
how do we get the value for V in one mole of interactions?
V = Q₁Q₂/4πℇ₀r
V = potential energy, J Q = charge r = distance between the charges, m
V x NA = J/mol
what must V be divided by when an interaction takes place not in a vacuum?
relative permittivity
ℇr = ℇ/ℇ₀
V/ℇr
give the equation for a dipole-dipole interaction that is:
- linear
- at an angle
V = -μ₁μ₂/2πℇ₀r³
V = -μ₁μ₂/4πℇ₀r³ (1 - 3cos²θ)
give the equation for charge-dipole interaction that is:
- linear
- at an angle
V = -μ₁Q₂/4πℇ₀r²
V = -μ₁Q₂/4πℇ₀r² x cosθ
distance is taken from the charge to the middle of the dipole (midpoint between two charges that make the dipole)
what is the charge of an electron?
-1.602 x 10-19 C
how do convert from
nm - m?
pm - m?
1 nm = 10-9 m
1pm = 10-12 m
