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Higher Chemistry - 2021/2022 > Unit 1 - Chemical Changes And Structure > Flashcards

Unit 1 - Chemical Changes And Structure Flashcards

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1
Q

How do metallic bonds form and what properties to they have

?

A 
Lattice
Between two metals
Delocalised electrons
Positive charged ions
Conduct electricity
Relatively strong bonds
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2
Q

What determines the strength of metallic bonds?

A

The greater the number of metallic bonds, the greater the charge on the metal ions, the greater the strength of the metallic bond and so increased mp and bp

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3
Q

How do monatomic gases exist?

A

As separate or discrete atoms.
Held together when cooled by intermolecular forces
e.g. Helium, Neon, Argon - Noble gases

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4
Q

What is an example of a covalent molecular gas?

A

Diatomic gases that are covalently bonded.

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5
Q

What is the trend for the strength of intermolecular forces down a group?

A

Down the groups, the atoms increase in size, which increases the number of electrons. This increase in electrons increases the strength of the intermolecular forces between the molecules, as well as the strength of the covalent bonds, thus increases the mp and bp

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6
Q

Give an example of a covalent molecular solid?

A

Sulphur

Phosphorous

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7
Q

What structure and properties does a diamond have?

A 
Covalent network
All bonds are covalent
No intermolecular forces
Very high mp and bp
Very hard substance
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8
Q

Why does graphite conduct electricity but diamonds don’t?

A

Graphite has free delocalised electrons that allow electricity to pass through while all of diamonds electrons are bonded

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9
Q

What is covalent radius?

A

Half the distance between two covalently bonded atoms of an element

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10
Q

What is trend for covalent radius down a group?

A

Down a group, the number of filled electron shells increases, which produces a shielding effect, preventing the outer electrons from being strongly attracted to the nucleus, thus increasing the covalent radius

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11
Q

What is the trend for covalent radius across a period?

A

Across a period, the number of protons increase, which increases the nuclear charge. This attracts the electrons closer to the nucleus and so decreases the covalent radius.

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12
Q

Why can’t the covalent nucleus be measured for noble gases?

A

Noble gases are monatomic and so do not bond for the covalent radius to be measured

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13
Q

What is electronegativity?

A

Electronegativity is a measure of an atoms nuclear attraction for the electrons in a covalent bond - can find on pg12 of data booklet

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14
Q

Trend for electronegativity down a group?

A

Down a group, the number of filled electron shells increase which increases the shielding effect, preventing the outer electrons from being strongly attracted to the nucleus. This decreases the electronegativity values.

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15
Q

What is the trend for electronegativity across a period?

A

Across a period, the number of protons increase, increasing the nuclear charge, attracting the outer electrons closer to the nucleus. This increases the electronegativity values.

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16
Q

Why is electronegativity described as a periodic property?

A

There is a clear trend across a period and down a group

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17
Q

Why aren’t there electronegativity values for the noble gases?

A

Monatomic as they have full electron shells and therefore have no bonding electrons

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18
Q

What is ionisation energy?

A

The energy required to removed one electron from one mole of an atom in a gaseous state.

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19
Q

Trend for ionisation energy across a period?

A

Across a period, the number of protons increase, which increases the nuclear charge that attracts the outer electrons closer to the nucleus. Therefore the ionisation energy increases as more energy is required to remove an outer electron.

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20
Q

Trend for ionisation energy down a group?

A

Down a group, the number of filled electron shells increase which increases the shielding effect, preventing the outer electrons from being strongly attracted to the nucleus. This decreases the ionisation energy as less energy is required to remove an outer electron.

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21
Q

When are ionic bonds formed?

A

When there is a large difference in electronegativity values between a metal and a non metal

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22
Q

Properties of ionic compounds?

A

High mp and bp
Solid at room temperature
Conduct electricity when molten or in solution because ions are delocalised

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23
Q

How do covalent bonds form?

A

Shared pair of electrons between non metals

24
Q

Types of intermolecular forces?

A

London Dispersion Forces (LDF’s) (Also known as temporary dipole to temporary dipole interactions)
Permanent dipole to permanent dipole interactions
Hydrogen bonding

25
Q

What intramolecular bonds make what intermolecular forces?

A

Non Polar Covalent Molecules -> London Dispersion Forces
Pure Covalent Molecules -> London Dispersion Forces
Polar Covalent Molecules -> Permanent Dipole to Permanent Dipole Interactions or Hydrogen Bonding

26
Q

What is defined as pure covalent bonds?

A

When there is no difference in electronegativity values - e.g. diatomic elements

27
Q

What determines the overall polarity of a molecule?

A

If there is symmetry

28
Q

When do non polar bonds form?

A

When there is a electronegativity difference between 0 and 0.4

29
Q

When do polar bonds form?

A

When the electronegativity difference is between 0.4 and 1.7

30
Q

When do hydrogen bonds form?

A

When the electronegativity value is over 1.7

31
Q

Is oxygen polar or non polar?

A

Polar

32
Q

What is the test for polarity?

A

If it deflects from a charged rod (moves towards rod) it is polar.

33
Q

How do you work out if a molecule is polar or non polar?

A 
Draw structure
Add electronegativity values
Count how many polar bonds there are
Count how many non polar bonds there are
Symmetry? (If polar molecules are devisable by two, cancel out)
Can it cancel out?
If yes, non polar
If no, polar
34
Q

What increases the strength intermolecular bonds?

A

The number electrons

35
Q

Where do hydrogen bonds form?

A

Between Hydrogen and either Nitrogen, Fluorine or Oxygen. Between molecules, not atoms

36
Q

What is responsible for the high boiling point of water?

A

Hydrogen bonds

37
Q

How would you measure visocity?

A

Choose alcohols with similar mass
Apparatus -> measuring cylinder, bung, timer, ball bearing
Method -> turn measuring cylinder upside down and time how long it takes for the ball bearing to reach the stopper.
The longer the ball takes, the more viscous the liquid

38
Q

What does the viscosity of a liquid say about the intermolecular bonds?

A

How many hydrogen bonds there are in the liquid

39
Q

What is miscability?

A

How well a something mixes

40
Q

What is solubility?

A

How well something dissolves

41
Q

What is the best solvents for what?

A

“Like dissolves like”
Non polar substances are the best solvents for other non polar substances
Polar substances are the best solvents for other polar substances and ionic compounds

42
Q

How to write Redox Equations?

A

Write electron equation
Scale up electrons
Combine equations
Score out electrons

43
Q

What is reduction?

A

A gain of electrons

44
Q

What is oxidation?

A

A loss of electrons.

45
Q

What is an oxidising agent?

A

A substance which promotes the oxidation of another substance by accepting electrons - is reduced.

46
Q

What is a reducing agent?

A

A substance which promotes the reduction of another substance by donating electrons - is oxidised.

47
Q

Uses of oxidising agents?

A

Hydrogen Peroxide and Sulphur Dioxide - bleaching

Potassium Permanganate : antiseptic

48
Q

Where do you find the best reducing agents?

A

Top right corner of page 12 of the data booklet

49
Q

Where do you find the best oxidising agents?

A

Bottom left corner of page 12 in the data booklet

50
Q

How to write full REDOX equations?

A 
Write equation (usually given)
Balance main element (e.g. Cr, N, F)
Balance Oxygens by adding water
Balance hydrogen by adding H+ ions
Balance charge by adding electrons
51
Q

How to calculate titrations?

A 
Write equation and balance
Write mole ratio
Work out one side
Use mole ratio to transfer information to other side
Scale up if required
52
Q

Why would a result not be included in the average volume for a titration?

A

Not concordant

53
Q

How do you make a standard solution?

A

Take a substance of known mass and dissolve it in minimal amount of water
Transfer into a volumetric flask
Use deionised water to rinse out beaker and to ensure all remains are transfer into flask
Use deionised water to fill to known volume

54
Q

How do you perform a titration?

A
55
Q

What is an enzyme?

A

A biological catalyst

Higher Chemistry - 2021/2022 (2 decks)

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