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Higher Chemistry > Unit 1 > Flashcards

Unit 1 Flashcards

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1
Q

How to calculate the average rate

A

Time interval

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2
Q

What is Collision Theory?

A

The idea of reactions taking place by the reactant particle colliding with eachother

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3
Q

Collision Theory states that substances may only react with eachother if:

A

1- Their particles collide with eachother
2- These collisions have sufficient energy
3- The particles collide with the correct geometry

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4
Q

What is meant by the term Heterogeneous?

A

The catalyst is in a different state from the reactant

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5
Q

What is meant by the term Homogeneous?

A

The catalyst is in the same state as the reactant

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6
Q

What are enzymes?

A

Biological catalysts.

They are complex protein molecules which speed up specific chemical changes by homogeneous catalysis.

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7
Q

How do you calculate the relative rate?

A

t

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8
Q

How do you calculate the enthalpy change (∆H)?

A

products - reactants

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9
Q

What does Ea stand for?

A

Activation energy

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10
Q

Where is the activated complex situated?

A

The top (curve) of a graph

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11
Q

What happens in an exothermic reaction?

A

∆H value has a negative sign/value

Energy is lost

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12
Q

What happens in an endothermic reaction?

A

∆H value has a positive sign/value

energy is taken in

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13
Q

What does a catalyst provide in potential energy diagrams?

A

a different reaction pathway to the product

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14
Q

Features of a metallic lattice:

A
  • high density indicating closely packed together

- the outer electrons on a metal atom are “delocalised”

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15
Q

What kind of melting and boiling point do metals have?

A

high

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16
Q

What is said about metallic bonding?

A

said to be very strong

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17
Q

What are the 2 types of metal (shapes)?

A

Malleable and ductile

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18
Q

What are Malleable metals?

A

when metals can be bent and hammered into different shapes

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19
Q

What are Ductile metals?

A

Can be pulled and squeezed to produces wires

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20
Q

What is said about boiling points of alkali metals? (going down group 1)

A

Going down group 1, the boiling points decrease. This indicates the strength of the metallic bonding is getting weaker.
The outermost electron on each atom gets further away from the positive nucleus. This increasing distance reduces the strength of the metallic bonding.

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21
Q

What is said about boiling points of metals? (across group 3)

A

Boiling point increases; indicating boiling point is getting stronger
Going across group 3; the number of outermost electrons on each atom increases.
The more outer electrons on a metal atom, the stronger the metallic bonding.

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22
Q

What are monatomic elements?

A

Group 0 - noble gases

Don’t form bonds with other elements

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23
Q

What are London Dispersion forces? and how are they formed?

A

Very weak forces

They are formed by the attraction between positive and negative charges (electrostatic attraction)

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24
Q

What is another name for London Dispersion forces?

A

Temporary dipole - Temporary dipole

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25
Q

What happens when a temporary dipole comes close to a neutral atom? and what does it from?

A

It affects the distribution of electrons, formation of an induced temporary dipole.

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26
Q

What are diatomic elements held together by?

A

Strong covalent bonds

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27
Q

What is a covalent bond?

A

The electrostatic attraction between a shared pair of electrons and the positively charged nuclei of the 2 atoms, which are sharing the electrons.

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28
Q

What is Atomic size?

A

the strength of some bonding is influenced by the size of the atoms involved.

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29
Q

What does Atomic size affect?

A

Affects physical properties such as melting point, boiling point and hardness

30
Q

What is the covalent radius?

A

Half the distance between the nuclei of bonded atoms.

31
Q

How do you calculate the density?

A

Mass g
———— = ——
Volume cm3

32
Q

What is the first ionisation energy?

A

The energy required to remove 1 mole of electrons from 1 mole of atoms in the gasous state

33
Q

What is the equation for the first ionisation energy?

A

E (g) –> E+ (g) + e-

34
Q

What happens when you increase the ionisation energy across a period?

A

increase nuclear charge, same number filled energy levels

35
Q

What happens when you decrease the ionisation energy down a group?

A

outer electron further from nucleus

36
Q

What elements are described as metallic?

A

All metals

37
Q

Which elements are described as covalent network?

A

Boron, carbon and silicon

38
Q

Which elements are described as covalent molecular (discrete covalent)?

A

Hydrogen, nitrogen, oxygen, fluorine, phosphorus, sulfur and chlorine

39
Q

Which elements are described as monatomic?

A

noble gases

40
Q

What is the second ionisation energy?

A

Energy required to remove a second electron from every atom, once a first electron has already been removed

41
Q

What is the equation for the second ionisation energy?

A

E+ (g) –> E2+ (g) + e-

42
Q

What is the ionic bond?

A

The electrostatic attraction between a positive and negative ion.

43
Q

Features of the ionic bond?

A

Very strong and requires a lot of energy to break

44
Q

What is said about all ionic compounds?

A

Solids at room temperature and have a high melting point.

45
Q

What is a covalent molecular compound?

A

A compound which is al liquid or a gas at room temperature

46
Q

What are polar covalent bonds?

A

When both atoms involved in covalent bonding are the same, the pair of electrons in the bond experiences the same attractive force from each nuclei.

47
Q

What is the name given when electrons are “equally shared”?

A

A pure covalent bond

48
Q

What happens when it is “unequal sharing”

A

become slightly negatively charged δ- and slightly positively charged δ+

49
Q

What is the name given when the bond has a δ+ and δ-?

A

Permanent dipole

50
Q

What is electronegativity?

A

is a measure of the attraction an atom that is involved in a covalent bond for the shared electrons of the bond

51
Q

“the larger the electronegativity value…

A

The stronger the attraction for the electrons in a covalent bond”

52
Q

What is a potential energy diagram used for??

A

Used to show the energy pathway for a chemical reaction

53
Q

What is Enthalpy?

A

A measure of the chemical potential energy contained in a substance

54
Q

What is the activation energy?

A

The energy required by colliding molecules to form the activated complex

55
Q

Why does electronegativity decrease down a group?

A
  • as the atomic size increases, the shared pair of electrons are further away from nucleus and are attracted less strongly
  • there is a greater screening effect because there are more shells of inner electrons between the shared pair of electrons and the nucleus
56
Q

Why does electronegativity increase across a period?

A

the positive nuclear charge is increasing and therefore the atoms exert a stronger pull on the shared pair of electrons

57
Q

why does the ionisation energy increase across a period from left to right?

A

more energy is required to remove an electron on moving from left to right because the positive nuclear charge is increasing and the atoms are getting smaller, so the negative electron is closer to the positive nucleus

58
Q

Why does the ionisation energy decrease down a group ?

A

less energy is required to remove an outer electron on moving down a group because the outer electron to be removed is in a shell further away from the nucleus.

59
Q

What are the Van der Waals forces?

A
  • London dispersion forces
  • Polar-polar attractions
  • Hydrogen bonding
60
Q

What is a dipole?

A

a term used to describe molecules in which an unequal distribution of charge results in one side of a molecule becoming slightly positively charged δ+ while the other side is slightly negatively charged δ-

61
Q

What is a polar molecule?

A

a molecule with a permanent dipole

62
Q

Why are intermolecular forces important?

A

to determine whether a compound will dissolve in a solvent or not

63
Q

What does it mean when the intermolecular forces are fairly similar?

A

the two types of molecules will be able to mix and move amongst each other easily (like-dissolves-like)

64
Q

What is another name for polar-polar molecules?

A

permanent dipole- permanent dipole

65
Q

What is hydrogen bonding?

A

the name given to unusually strong permanent dipole-permanent dipole interactions that arise between highly polar molecules

66
Q

What 3 elements have electronegativity values greater than hydrogen and which forms a hydrogen bond?

A

oxygen, nitrogen and fluorine

67
Q

What is viscosity?

A

a measure of how much the molecules tend to stick together. the more viscous the liquid, the less runny it is

68
Q

Which intermolecular force has the highest boiling point?

A

hydrogen bonding

69
Q

Which intermolecular force has the lowest boiling point?

A

London dispersion forces

70
Q

What happens when water freezes?

A

its volume increases due to the hydrogen bonding between the water molecules causing the water molecules to form the open structure of ice

Higher Chemistry (3 decks)

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