Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PPQS > Chem - topic 2 > Flashcards

Chem - topic 2 Flashcards

1
Q

What are molecular ions?

A

Covalently bonded atoms that lose or gain electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Which are the 4 elements that don’t tend to form ions and why?

A

The elements are beryllium, boron, carbon and silicon
Requires a lot of energy to transfer outer shell electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What determines the strength of an ionic bond?

A
  • ionic radius and ionic charge
  • ionic bonding is stronger and the melting points higher when the ions are smaller and/ or have higher charges
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Explain the trend in ionic radius down a group

A

Ionic radii increases going down the group. This is because down the group the ions have more shells of electrons and thus the outermost electron experience less pull from positive nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Explain the trend in ionic radius for this set of isoelectronic ions, eg N3- to Al3+

A

There are increasing numbers of protons from N to F and then Na to Al but the same number of electrons. Therefore nuclear attraction between the outermost electrons and nucleus increases and ions get smaller

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the physical properties of ionic compounds

A
  • High melting points
  • non conductor of electricity when solid
  • conductor of electricity when in solution or molten
  • brittle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Define metallic bonding

A

Electrostatic attraction between the positive metal ions and the sea of delocalised electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Giant ionic lattices have high or low melting and boiling point? Explain your answer

A

They have high melting and boiling point because a large amount of energy is required to overcome the electrostatic bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

In what type of solvents do ionic lattices dissolve

A

Polar solvents eg. water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why are ionic compounds soluble in water

A

Water has a polar bond. Hydrogen atoms have a 1+ charge and oxygen atoms have a 2- charge. These charges are able to attract charged ions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is it calles when atoms are bonded by a single pair of shared electrons

A

single bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the effect of multiple covalent bonds on bond length and strength

A

Double/triple bonds exert greater electron density therefore the attraction between nucleus and electron is greater resulting in a shorter and stronger bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a lone pair

A

Electrons in the outer shell that are not involved in the bonding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is a dative covalent bond?

A

A bond where both of the shared electrons are supplied by one atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How are oxonium ions formed?

A

Formed when acid is added to water, H3O+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Draw a dot and cross diagram to show bonding in Al2Cl6

A

Look at a diagram (2 Cl dative bond towards Al)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does expansion of the octet mean?

A

When a bonded atom has more than 8 electrons in the outer shell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the types of covalent structure

A
  • Simple molecular lattice
  • Giant covalent lattice
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe the bonding in simple molecular structures

A

Atoms within the same molecule are held by strong covalent bonds and different molecules are held by weak intermolecular forces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Why do simple molecular structures have low melting and boiling points?

A

Small amounts of energy is enough to overcome the intermolecular forces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Why do simple molecular structures not conduct electricity

A

They have no free charged particles to move around

22
Q

Simple molecular structures dissolve in what type of solvent?

A

Non polar solvents

23
Q

Give example of giant covalent structures

A
  • diamond
  • graphite
  • silicon dioxide, SiO2
24
Q

List some properties of giant covalent structures (3)

A
  • high melting and boiling point
  • non conductors of electricity, except graphite
  • insoluble in polar and non polar solvents
25
Q

How does graphite conduct electricity

A

Delocalised electrons present between the layers are able to move freely carrying the charge

26
Q

Draw and describe the structure of a diamond

A

3D tetrahedral structure of C atoms, with each C atom bonded to four others

27
Q

What is the shape diagram and bond angle for 3bp 0lp (eg BCl3)

A

Trigonal planar - 120

28
Q

What is the shape diagram and bond angle for 2bp 0lp (eg BCl2)

A

Linear - 180

29
Q

What is the shape diagram and bond angle for 4bp 0lp (eg CH4)

A

Tetrahedral - 109.5

30
Q

What is the shape diagram and bond angle for 5bp 0lp (eg PCl5)

A

Trigonal bipyramid - 90 and 120

31
Q

What is the shape diagram and bond angle for 6bp 0lp (eg SF6)

A

Octahedral - 90

32
Q

What is the shape diagram and bond angle for 3bp 1lp (eg NH3)

A

Pyramidal - 107

33
Q

What is the shape diagram and bond angle for 2bp 2lp (eg H2O)

A

Non linear - 104.5

34
Q

What is the shape diagram and bond angle for NH4+

A

Tetrahedral - 109.5
[diagram]+

35
Q

Define electronegativity

A

The ability of an atom to attract the pair of electrons (the electron density) in a covalent bond

36
Q

What does it mean when the bond is non polar

A

The electrons in the bond are evenly distributed

37
Q

How is a polar bond formed

A

Bonding atoms have different electronegativities

38
Q

Why is H2O polar, whereas CO2 is non polar?

A

CO2 is a symmetrical molecule, so there is no overall dipole

39
Q

What is meant by intermolecular force?

A

Attractive force between neighbouring molecules

40
Q

Describe permanent dipole induced dipole interactions

A

When a molecule with a permanent dipole is close to other non polar molecules it causes the non polar molecule to become slightly polar leading to attraction

41
Q

Describe permanent dipole- permanent dipole interactions

A

Some molecules with polar bonds have permanent dipoles → forces of attraction between those dipoles and those of neighbouring molecules

42
Q

Describe London forces

A
  • London forces are caused by random movements of electrons
  • This leads to instantaneous dipoles
  • Instantaneous dipole induces a dipole in nearby molecules
  • Induced dipoles attract one another
43
Q

Does boiling point increase or decrease down the noble gases group? Why?

A

Boiling point increases because the number of electrons increases and hence the strength of London forces also increases

44
Q

Why is ice less dense than liquid water?

A
  • In ice, the water molecules are arranged in a orderly pattern. It has an open lattice with hydrogen bonds
  • In water, the lattice is collapsed and the molecules are closer together
45
Q

Why does water have a melting / boiling point higher than expected?

A

Hydrogen bonds are stronger than other intermolecular forces so extra strength is required to overcome the forces

46
Q

What type of intermolecular forces do alkanes have? Why?

A

London force → induced dipole-dipole interaction, because the bonds are non polar

47
Q

What happens to the boiling point as alkane chain length increases? Why?

A

The boiling point increases because there is more surface area and so more number of induced dipole-dipole interaction. Therefore more energy required to overcome the attraction

48
Q

Does a branched molecule have lower or higher boiling point compared to equivalent straight chain? Why?

A

The branched molecule has a lower boiling point because they have fewer surface area and hence less induced dipole-dipole interactions

49
Q

Are alkanes soluble in water? Why?

A

Insoluble because the hydrogen bonds in water are stronger than alkanes’ London forces of attraction

50
Q

Are alcohols soluble in water? Why does solubility depend on chain length?

A

Soluble when short chain → OH hydrogen bonds to hydrogen bond in water
Insoluble when long chain → non polarity of CH bond takes precedence

51
Q

Explain the trend of boiling temperatures of hydrogen halides HF to HI

A

There is a general increase of boiling point from Hal to HI which is caused by increasing London forces because of number of electrons. There is a big drop in boiling point from HF to HCl because fluorine is very electronegative therefore the hydrogen bonding is much stronger

PPQS (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions