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[OBSELETE] S - Chem > topic 2 > Flashcards

topic 2 Flashcards

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1
Q

what are isoelectronic ions

A

atoms, ions or molecules that have the same electronic configuration/structure

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2
Q

what is the trend in ionic radii of a set of isoelectronic ions across a period

A

if the number of protons increase electrons are more attracted to the nucleus
so ionic radii falls

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3
Q

what provides evidence for the existence of ions

A

1- physical properties such as electrical conductivity, ionic substances are brittle
2- electron density maps
3- migration of ions using copper (III) dichromate

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4
Q

how does the migration of ions prove the existence of ions

A

copper ions are blue and positive -> attracted to cathode
dichromate ions are orange and negative -> attracted to the anode

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5
Q

what is a covalent bond

A

strong electrostatic attraction between two nuclei an the shared pair of electrons between them

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6
Q

recall the names of shapes of molecules

A

linear
trigonal planar
bent
tetrahedral
trigonal pyramidal
trigonal bipyramidal
octahedral
square planar
T shape
seesaw
square pyramid

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7
Q

how many bonding/lone pairs does a linear molecule have- draw the shape and label the bond angle

A

2 bond pairs
180 degrees

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8
Q

how many bonding and/lone pairs does a trigonal planar molecule have- draw the shape and label the bond angle

A

3 bond pairs
120 degrees

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9
Q

how many bonding and/lone pairs does a bent molecule have- draw the shape and label the bond angle

A

1 lone pair
2 bond pairs
<120 degrees

or

2 bond pairs
2 lone pairs
<109 degrees

refer to VESPR table for shape

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10
Q

how many bonding and/lone pairs does a tetrahedral molecule have- draw the shape and label the bond angle

A

4 bond pairs
109 degrees

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11
Q

how many bonding and/lone pairs does a trigonal pyramidal molecule have- draw the shape and label the bond angle

A

3 bond pairs
1 lone pair
<109 degrees

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12
Q

how many bonding and/lone pairs does a trigonal bipyramidal molecule have- draw the shape and label the bond angle

A

5 bond pairs
90 and 120 degrees

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13
Q

how many bonding and/lone pairs does a seesaw molecule have- draw the shape and label the bond angle

A

1 lone pair
4 bond pairs
<120 degrees and <90 degrees

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14
Q

how many bonding and/lone pairs does a T shape molecule have- draw the shape and label the bond angle

A

2 lone pairs
3 bond pairs
<90 degrees

or

3 bond pairs
3 lone pairs
<90 degrees refer to VESPR table for shape

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15
Q

how many bonding and/lone pairs does an octahedral molecule have- draw the shape and label the bond angle

A

6 bond pairs
90 degrees

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16
Q

how many bonding and/lone pairs does a square pyramidal molecule have- draw the shape and label the bond angle

A

1 lone pair
5 bond pairs
<90 degrees x2

17
Q

how many bonding and/lone pairs does a square planar molecule have- draw the shape and label the bond angle

A

2 lone pairs
4 bond pairs
90 degrees

18
Q

what causes bonds to be polar

A

electronegativity differences as electrons in the bond arent shared equally

19
Q

how can you predict whether a molecule is polar

A

whether the molecule is symmetrical
whether the molecule has polar bonds

20
Q

how do london forces form

A

caused by an uneven distributions of electrons within an atom
this results in a slight negative and slight positive charge on either side of the atom -> temporary dipole
this temporary dipole can induce a temporary dipole on a neighbouring molecule

21
Q

how does a permanent dipole force arise

A

the forces are between the slightly positive end of one polar molecule and the slightly negative end of another polar molecule
the slight charges are due to permanent dipoles which arise when theres an electronegative atom or a halogen

22
Q

how do hydrogen bonds arise

A

they result from the attractive force between a hydrogen atom, which is covalently bonded to a very electronegative atom, and another very electronegative atom

23
Q

how does hydrogen bonding arise in water

A

hydrogen bonds form between neighbouring hydrogen atoms and oxygen atoms of adjacent water molecules

24
Q

how does hydrogen bonding arise between ammonia (NH3) molecules

A

electronegativity difference between hydrogen and nitrogen which means that a partial charge develops on them

25
Q

why does water have a relatively high bpt

A

due to hydrogen bonding
requires more energy to overcome as its the strongest I force

26
Q

why is ice less dense than water

A

this is because when hydrogen bonds form it pushes water molecules further apart which decreases the density

27
Q

what is the trend in boiling temperatures of alkanes with increasing chain length

A

stronger/increased number of london forces as theres more electrons in longer chained alkanes

28
Q

what is the effect of branching in the carbon chain on boiling temperatures of alkanes

A

as branching increases, the surface area of the molecule decreases
smaller area of contact
london forces decrease therefore bpt decreases

29
Q

why are alcohols less volatile compared to alkanes with a similar number of electrons

A

this is because alcohols can form hydrogen bonds between molecules whereas alkanes only form london forces which are weaker

30
Q

what does volatile mean

A

a substance that is readily changing from a solid or liquid to a gas

31
Q

why is water a good solvent for some ionic compounds

A

ions attracted to the water molecules
ions hydrated

32
Q

why is water used to dissolve simple alcohols

A

water can form hydrogen bonds with them

33
Q

why is water a poor solvent for polar molecules and halogenoalkanes

A

this is because they cant form hydrogen bonds with water

34
Q

when are non aqueous solvents used

A

used for compounds that have similar intermolecular forces to those in the solvent

35
Q

why are non polar substances soluble in hexane and not water

A
  • insoluble in water as it cant hydrogen bond to water
  • this is because none of the hydrogen atoms in the non polar substance have a slight positive charge
  • its soluble in hexane because the london forces in the substance and hexane are similar in strength
36
Q

why are ionic/ polar substances soluble in water and not hexane

A

ionic substances ions are hydrated
the enthalpy of hydration is greater than the energy needed to break apart the lattice
its insoluble in hexane because any london forces that form between the ionic substance and hexane will be smaller in size than the forces between the ions in the ionic/polar substance

[OBSELETE] S - Chem (19 decks)

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