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chemistry > structure 1 > Flashcards

structure 1 Flashcards

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1
Q

What is an element?

A

primary constituents of matter which cannot be broken down into simpler substances

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2
Q

What is a mixture?

A

one or more element or compound in no fixed ratio that aren’t chemically combined, so can be separated by physical methods

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3
Q

What is a compound?

A

atoms of different elements chemically bonded in fixed ratios

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4
Q

What is the difference between a homogeneous and heterogeneous mixture?

A

heterogeneous - non-uniform composition and substances have different properties and interactions - oil and water
homogeneous - uniform composition where all substances have the same properties and interactions - alloys

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5
Q

What is crystallization?

A

using evaporation and condensation to collect a pure solid

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6
Q

What is filtration?

A

separates an insoluble solid from a liquid using a filter paper and funnel

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7
Q

What is distillation?

A

separates mixtures of solvents with different boiling points

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8
Q

what is chromatography?

A

separates substances with different solubilities

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9
Q

What is the kinetic molecular theory?

A

a model used to explain the physical properties of matter and their changes of states

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10
Q

What are the properties of solids?

A
  • particles arranged closely in a regular pattern with all particles touching
  • particles vibrate in a fixed position
  • fixed shape and volume
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11
Q

What are the properties of liquids?

A
  • particles closely arranged, but not in a regular pattern
  • no fixed shape and volume
  • move slightly
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12
Q

What are the properties of gases?

A
  • particles fully spread out
  • particles slide around quickly
  • no fixed shape or volume
  • can be compressed
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13
Q

What is kinetic energy?

A

energy from the movement of particles with an inverse relationship to mass and velocity

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14
Q

What is the boiling point?

A

temperature at which vapor pressure is equal to external pressure

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15
Q

What is vapor pressure?

A

pressure exerted by the gas in equilibrium with a solid or liquid in a closed container at a given temperature

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16
Q

What is temperature?

A

measure of the average kinetic energy

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17
Q

What happens to pressure and boiling points at higher altitudes?

A

lower altitude = higher pressure = higher boiling point
higher altitude = lower pressure = lower boiling point

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18
Q

What is absolute temperature?

A

lowest temperature when there is no movement of particles at 0C or -273K

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19
Q

How can you convert between K and C?

A

k –> C = -273.15
C –> k = +273.15

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20
Q

How can you describe the changing states from a graph?

A
  1. as energy increases, temperature increases (solid)
  2. melting - solid to liquid with no change in temperature
  3. as energy increases, temperature increases (liquid)
  4. boiling - liquid to gas with no change in temperature
  5. as energy increases, temperature increases (gas)
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21
Q

What is the mass number?

A

number of protons and neutrons

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22
Q

What is the atomic number?

A

number of protons which is equal to the number of electrons

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23
Q

What are ions?

A

atoms that have lost (cations) or gained (anions) electrons so are positive or negatively charged

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24
Q

What are cations and anions?

A

cations - positive ions
anions - negative ions

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25
Q

What is RAM?

A

average mass of all isotopes relative to the atom of carbon 12

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26
Q

What is a plasma?

A

an atom that has been stripped of it’s electrons so is a positive ion with loosely attracted electrons but only exists at high temperatures and pressure

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27
Q

What is an isotope?

A

atoms with the same number of protons and electrons but different amount of neutrons

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28
Q

What are some uses of isotopes?

A
  • carbon dating
  • nuclear power stations
  • tracing pollution levels
  • PET scans and tracers
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29
Q

How do you work out abundance of an isotope?

A

(% abundance of isotope x Mr of isotope) / 100

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30
Q

Why is mass spectra used?

A

determines the relative atomic masses of elements from their isotopic composition to form a mass spectrum

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31
Q

How is mass spectra carried out?

A
  1. element is vaporized to analyze the individual atoms and are ionized bu high energy electrons to knock off electrons and produce a positive ion
    X(g) + e- –> X+(g) + 2e-
  2. positive ions are attracted to the negative plate and deflected by a magnetic field at right angles
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32
Q

How can you use mass spectra to identify the molecular mass of the substance you are investigating?

A

look at the parent ion peak, which is the peak furthest to the right in the mass spectrum

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33
Q

How is mass spectra interpreted?

A

deflection is inversely proportional to mass/charge

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34
Q

What is fragmentation?

A

Collisions during the ionization stage are so energetic between the electron and the molecule that the molecule fragments and this can be used to identify the structure of a compound

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35
Q

What is an emission spectra?

A

produced when atoms emit photons when electrons in excited states to lower energy levels

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36
Q

What is the line emission spectrum of hydrogen?

A

provides evidence for the existence of electrons in discrete energy levels which converge at higher energies

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37
Q

What is an absorption spectra?

A

gains electrons at jumps up to a higher energy level

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38
Q

What is an emission spectra?

A

loses electrons and jumps down to lower energy level

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39
Q

How do atoms give out different colors?

A

an electric discharge is passed through vapor of the element or heated in a Bunsen burner

40
Q

What is frequency?

A

amount of waves passing a point per second

41
Q

How do you work out wave speed?

A

wave speed = frequency x wavelength

42
Q

What is the electromagnetic spectrum?

A

different types of waves with frequency increasing and wavelength decreasing from left to right

43
Q

What is the order of the electromagnetic spectrum?

A

radio, microwaves, infrared, visible, UV, x-ray, gamma ray

44
Q

What is the difference between a continuous and a line spectrum?

A

continuous spectrum - shows all frequencies
line spectrum - shows certain frequencies

45
Q

What is the ground and excited state of an atom?

A

ground state - lowest energy and most stable arrangement where the electron is closest to the nucleus
excited state - highest energy level with least stable arrangement where the electron is furthest from the nucleus

46
Q

What is a photon?

A

a packet of light which corresponds to a particular wavelength and frequency
E electron = E photon = hf

47
Q

What are the Paschen, Balmer and Lyman series?

A

paschen - falls to energy level 3 (emits IR)
balmer - falls to energy level 2 (emits visible light)
lyman - falls to energy level 1 (emits UV)

48
Q

Why do lines converge at higher energies?

A

as the energy level increases, the energy levels between adjacent levels decreases, causing the spectral lines to converge at higher energies

49
Q

What is the uncertainty principle?

A

we cannot know the certain location of an electron and are located in orbitals where there is a high probability of finding an electron

50
Q

What is an energy level?

A

shells around the nucleus that contain sub-shells in a specific shape

51
Q

What are orbitals?

A

holds 2 electrons with a defined energy state

52
Q

How many electrons can each energy level hold?

A

s=2 / p=6 / d=10 / f=14

53
Q

What is the first energy level made out of?

A
  • contains 1s orbital
  • maximum of 2 electrons in the level
54
Q

What is the second energy level made out of?

A
  • contains 1s orbital and 3 2p orbitals
  • maximum of 8 electrons in the level
55
Q

What is the third energy level made out of?

A
  • contains 1s orbital, 3p orbitals, 5d orbitals
  • maximum of 18 electrons in the level
56
Q

What is Hund’s third rule?

A

electrons fill up empty orbitals first before filling up occupied orbitals

57
Q

What is the Aufbau principle?

A

electrons are placed into the lowest energy level first, demonstrated by an arrow-in-box diagram

58
Q

What is the Pauli-exclusion principle?

A

no more than 2 electrons can occupy 1 orbital and they must spin in opposite directions to reduce repulsion

59
Q

What are valence electrons?

A

outer shell electrons

60
Q

What does ionization correspond to?

A

limit of convergence at higher frequency corresponds to ionization which can be used to find ionization energy

61
Q

What is the electronic configuration of Cu and Cr?

A

Cr = 1s 2s2 2p6 3s2 3p6 3d3 4s1
Cu = 1s2 2s2 2p6 3s2 3p6 3d10 4s1

62
Q

What is ionization energy?

A

amount of energy required to remove 1 mole of electrons from 1 mole of atoms in the gaseous state

63
Q

What is successive ionization energy?

A

energy to remove another mole of electrons from a mole of atom in the gaseous state

64
Q

What evidence is there for successive ionization energy?

A

sub-levels in atoms - 2s can hold 2 electrons and 2p can hold 6 electrons and there is a jump in ionization energy as electrons need to be removed from closer to the nucleus

65
Q

What are the successive ionization energies like for transition metals?

A

Ca = has a sharp increase in ionization energy as third electron is removed from the 3p orbital
Ti = has a more gradual change as the outer electrons from 3d and 4s are close in energy

66
Q

What are trends of ionization energy?

A

across the period = ionization energy increases as ENC increases, so there is an increased attraction
down the group = ionization energy decreases as the shell number increases and attraction decreases
- regular discontinuities provide evidence for the existence of subshells

67
Q

What are the 4 equations involving moles?

A

moles = mass / Mr
moles = volume (dm3) / 24
moles = volume / molar volume
moles –> particles = x Ar
particles –> moles = / Ar

68
Q

What is Avogadro’s constant?

A

one mole contains 6.02 x 10^23 elementary entities with SI unit of the mol

69
Q

What is an elementary entity?

A

an atom, molecule, ion, electron or any other particle or group of specified particles

70
Q

What is the difference between Mr and Ar?

A

Mr = relative formula mass = sum of Ar
Ar = relative atomic mass

71
Q

What is the empirical formula?

A

simplest whole number ratio of atoms in a compound

72
Q

What is the molecular formula?

A

shows all the atoms present in a molecule
molecular formula = (mass of empirical formula) x

73
Q

How can you work out empirical formula of MgO?

A
  1. calculate moles of magnesium used
  2. calculate the moles of oxygen that reacted from the increase in mass
  3. express ratio of Mg:O in the simplest form
  4. ratio of moles is equal to ratio of atoms
74
Q

How can you convert % by mass to empirical formula?

A
  1. convert each element to moles by dividing mass by Mr
  2. divide the moles by the smallest number
  3. approximate to the nearest whole number
75
Q

What is molar concentration?

A

concentration (gdm3) = mass / volume
molar concentration (moldm3) = mol / volume

76
Q

What is the solution, solvent and solute?

A

solution - mixture of the solute dissolved in the solvent
solvent - the liquid in which the solute dissolves in
solute - the solid in which the solvent dissolves

77
Q

What is a standard solution?

A

chemicals prepared to a known concentration and transferred to a volumetric flask

78
Q

What is serial dilution?

A

slowly reducing concentration by a fixed amount each step

79
Q

What is UV spectroscopy?

A

quantitative technique used to measure the absorbance of a substance

80
Q

What is a calibration curve?

A

a curve that shows the absorption of a unknown substance to determine it’s concentration

81
Q

What is Avogadro’s law?

A

moles is directly proportional to volume

82
Q

What are the 5 ideal gas assumptions?

A
  1. volume of gas is negligible
  2. there are no attractive forces between particles
  3. large number of identical molecules
  4. collisions are elastic as kinetic energy is conserved
  5. particles have a range of speed and motion
83
Q

What is an ideal gas?

A

particles with a negligible volume and no attractive forces

84
Q

What is a real gas?

A

deviates from ideal gas laws and has attractive forces and a volume

85
Q

When does a real gas differ from and ideal gas?

A

low temperatures and high pressures

86
Q

What is the pressure law?

A

pressure is directly proportional to temperature at a fixed volume

87
Q

What is molar volume?

A

volume occupied by one mole of a gas under standard conditions

88
Q

What is Boyle’s law?

A

pressure is inversely proportional to volume at a fixed temperature

89
Q

What is Charles’ Law?

A

volume is directly proportional to temperature at a fixed pressure

90
Q

What is the ideal gas equation?

A

pV = nRT

91
Q

What are limitations of the ideal gas model?

A
  1. volume isn’t negligible
  2. attractive forces exist
  3. doesn’t apply at high pressure and low temperatures
92
Q

What is the combined gas law equation?

A

(p1V1) / V1 = (p2V3) / V2

93
Q

what is gas pressure?

A

due to particles colliding with the wall
- increasing temperature increases pressure as the particles have more kinetic energy so collide more frequently and exert more force on the walls of the container

94
Q

what is the value for pv/rt for an ideal gas and what does a graph look like?

A

pv/rt = 1 for an ideal gas and has a horizontal graph

95
Q

what does a pv/nrt value smaller than and larger than 1 mean?

A

smaller than 1 - there are attractive forces between particles which reduce the speed of collisions, making them less energetic and decreasing pressure
larger than 1 - there is not a negligible volume and collisions between particles and walls of the container are more frequent than predicted

chemistry (28 decks)

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