chemistry - End of unit 1+2 test - Nuclear atom, electronic structure

mixture

non-pure substance with components that can be elements, compounds, or other mixtures. the components are not chemically bonded together so they retain their individual properties.

homogenous mixture

same (uniform) composition throughout the mixture. consists of only 1 phase

heterogenous mixture

does not have a uniform composition. consists of seperate phases

phases

region that is the same throughout, in terms of chemical composition and physical properties

filtration

separates insoluble solids from a liquid

residue is the solid left in the filtration paper

filtrate is the liquid that passes through the filter paper.

evaporation

remove a solvent from a solution to leave the solute

solvation

separate a mixture of 2 or more substances due to differences in solubility.

filtration then evaporation

distillation

separate solute and solvent from a solution (where the solute was a solid)

separate a mixture of 2 liquids with sufficiently different boiling points

distillation vs evaporation

distillation - solvent (or solvent + solute) = desired product

evaporation - solute = desired product

recrystallisation

purify solids which contain relatively small amounts of impurities

paper chromatography

separate various dyes in colored inks

separate mixture of sugars/amino acids

test purity of substances (more than 1 dot = impure

boyles law

at a constant temperature, the volume of a fixed mass of an ideal gas is inversely proportional to its pressure.

p ∝ 1/v

p = k/v

pv = k (k is a constant)

p1v1 = p2v2

(the product of the pressure and volume of an ideal gas at a particular temp is a constant and does not change as the pressure and volume change)

charles’ law

at a constant pressure, the volume of gas is directly proportional to temperature

v ∝ T

v1/t1 = v2/t2

(if the kelvin temp doubles, and pressure remains constant, the vol of gas doubles)

Gay - Lussac’s law

for a fixed mass of an ideal gas at a constant volume, the pressure is directly proportional to it’s absolute (kelvin) temp

p1/t1 = p2/t2

p ∝ T

features of an ideal gas

1. gas molecules are in constant random motion and move in straight lines

2. they behave as rigid spheres

3. pressure is produced by collisions from both the walls of the container and eachother

4. the collisions are elastic meaning no energy is lost

5. the average kinetic energy is proportional to the temperature

6. the intermolecular forces between molecules are negligible

7. the size of the molecules is negligible compared to the container

features of a real gas

1. the volume of the gas particles is not negligible

2. there are attractive forces between the molecules

3. collisions are not elastic

when do real gases deviate from the ideal gas model the most

at a low temperature and high pressure

overall gas law equation

an ideal gas is one that follows all laws of the ideal gas model exactly

p1v1 /T2 = p2v2/T2

temp must be in kelvin

ideal gas equation

relationship between P, V and T combined with avogadros law

PV = nRT

R = gas constant = 8.31

n = number of moles

when do gases have the same molar volume

when they are in the same conditions

find number of moles (n)

n = vol / molar volume

when they ask you to find molar volume

volume of 1 mol

n = 1

avogadros law

6.022 × 10 to the power of 23

number of particles per mole

equal volume of different gases, when measured at the same temperature and pressure, contain an equal number of particles

radio isotopes

radioactive isotopes that are unstable because of the numbers of subatomic particles they contain in their nuclei. their instability causes them to emit various forms of radiation

atoms

smallest particles remaining the properties of an element

protons

positive charge with a relative mass of 1

neutrons

mo charge with a relative mass of 1

electrons

negative charge with a relative mass of 1/2000 (of a proton)

hpw to find number of protons

same as number of neutrons

mass number

protons + neutrons

atomic number

number of protons in the nucleus

positive ions

formed when an atom loses an electron

negative ion

formed when an atom gains an electron

isotopes

atoms of the same element that have different numbers of neutrons. (same number of protons).

this effects the physical properties, not the behaviour in chemical reactions so much

calculating relative atomic mass

Calculating the relative atomic mass involves multiplying the mass of each isotope by its relative abundance, summing these values, and dividing by 100. The formula is:

Relative Atomic Mass = (Mass of Isotope 1 x Abundance of Isotope 1 + Mass of Isotope 2 x Abundance of Isotope 2 + ...) / 100

Note: Isotope masses are usually given in atomic mass units (u) and abundances as percentages.

wavelength

distance between 2 crests in an oscillating wave

frequency

number of waves that pass a point in 1 second (Hz)

mass spectrometer

used to determine the relative atomic mass of an element from its isotopic composition

physical properties affected in isotopes

1. melting point

2. rate of diffusion

heisenbergs uncertainty principle

it is impossible to state the exact position of an electron at a precise moment in time

aufbau building up principle 3 rules

pauli exclusion principle - only electrons with opposite spin can occupy the same orbital

hunds rule - every orbital in a sub level is occupied with single electrons of the same spin before pairing up

orbitals with lower energy are filled before those with higher energy

ground state

when an electron is where it should be

lyman series

sub level 1 - UV

balmer series

sub level 2 - IR

paschen series

sub level 3 - visible