Week 11

Question 1

Functional groups

Answer 1

A part of a molecule that has distinctive chemical properties
The same functional group will have similar chemical behaviour even when the rest of the molecule is different

Question 2

Bond vibrations

Answer 2

Most bond vibrations correspond to absorbing IR light
Exact vibrational frequency depends on bond strength

Question 3

Electric Dipole

Answer 3

An electric dipole is a separation of charges (positive and negative)
Unequal sharing or distribution of electrons between atoms

Question 4

Dipole moment

Answer 4

The product of the separation of the ends of a dipole and the magnitude of the charges

Question 5

Covalent bonds

Answer 5

Form when electrons are shared between atoms
Outer electrons are tightly held close to the nucleus
Delocalisation
Close overlap required
Short range, directional

Question 6

Metallic bonding

Answer 6

Outer electrons a long way from the metal, not held tightly
Multiple atoms can overlap without nuclei repelling
Does not require close overlap
Electrons can delocalise across the whole system
- conduct electricity

Question 7

Hydrogen bonding

Answer 7

creation of a hydrogen bond - intermolecular forces caused by dipole forming
Oxygen is electronegative so O-H bonds are polarised
Separation of charge to form a dipole
Can interact with other dipoles to form H-bonds

H-bonding is strong

Question 8

Can der Waals interactions

Answer 8

Bond energy < 5 Kjmol-1
Polarisation of an electron cloud by adjacent nucleus
Weak electrostatic interaction

Question 9

Waves

Answer 9

In phase waves are waves that are in sync and out of phase waves are waves that overlap but aren’t in sync

Question 10

Standing waves

Answer 10

Oscillates in time
Peaks/troughs do not move in space
Location of any wave cannot be accurately determined

Question 11

C = ^u

Answer 11

C = speed of light (3.00x10^8m/s)
^ = wavelength
V = frequency

Question 12

Wave particle duality

Answer 12

Wave theory of light cannot explain the photoelectric effect
When light is shone at metal plate, an electron is emitted
Light is not continuous like a wave
Light is discrete, quantised
-photons - particle of light

Question 13

Wave particle duality (2)

Answer 13

Night frequency waves = high energy particles
One photon with high enough energy can eject an electron
Many photons with low energy cannot eject an electron

Question 14

E = hv

Answer 14

E = energy of photon
h = plancks constant (6.626 c 10^-34 m^2.kg/s)
V = frequency of a proton

Question 15

Bohr model of the atom I

Answer 15

Potential energy of the electron in a hydrogen atom is quantised
Electron can only be found in specific energy levels - fixed distances from the nucleus
Energy increases with distance
Electron can move to higher level, but needs energy to do it
Photon of the exact specific energy absorbed

Question 16

Bohr model of the atom (2)

Answer 16

Electron can return to lower level, but will give out energy if it does
Photon of the exact specific energy emitted
Rydberg constant (Rh) = 2.179 x 10^-18J

Question 17

De broglie equation

Answer 17

^ = h/mv

^ = wavelength in m
H = plancks constant
M = mass of particle in kg
V = velocity of the particle in m/s

Question 18

Absorption and emission spectra

Answer 18

White light can be separated by wavelength using a prism
Some photons are absorbed to promote electrons to higher levels
- absorption spectrum
Some photons are emitted as electrons return to lower levels
- emission spectrum

Question 19

Electron as a standing wave

Answer 19

Electron in an atom is considered a circular standing wave
Must have an integer number of wavelengths
Wavelength related to energy
As n increases energy increases
Only certain energies are allowed - quantisation

Interference of standing waves results in covalent bonding