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Chemistry sem 1 > Structure Bonding and Equilibria > Flashcards

Structure Bonding and Equilibria Flashcards

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1
Q

What is covalent bonding

A

The formal sharing of electrons between two atoms, typically found in elements with high electronegativity or when the atoms have a small difference in electronegativity

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2
Q

What is ionic bonding

A

electrons being formally transferred from one atom to another to form a charged ionic compound, in compounds where constituent elements have a large electronegative difference

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3
Q

What is metallic bonding

A

elements with low electronegativity, electrons are delocalised

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4
Q

What is hydrogen bonding

A

electrostatic interaction, non-covalent interaction

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5
Q

In the van Arkel-Ketelaar Triangle, what values relate to what bonding

A

-where x is electronegativity
-delta x>2 - ionic bonding
-0.5<delta x<2 - polar covalent bonding
-delta x<0.5 - covalent bonding

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6
Q

What are the trends in ionisation energy across period 1

A

-number protons inc so nuc charge inc
-electrons are in the same area of space so theres no shielding. effective nuclear charge increases (Zeff), attractive between nucleus and electrons increase so IE increases
-dip at B-2p not penetrate 2s too well-Zeff is lower
-dip at O- 2e- in same p orbital so repulsion

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7
Q

what are the IE trends down group 1

A

-decreases
-principle quantum number increases, e- spend more time away from nucleus, less attraction
- not even trend (d orbital full small increase in Zeff) due to e- not efficiently shielding the add H+

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8
Q

what is the trend in electron gain enthalpy across period 1

A

same argument for for 1st IE of O but in reverse

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9
Q

what are the lattice enlthalpy trends down group 1

A

-decreases as ion size increases
-the greater the charge on the ion the greater the lattice enthalpy
-only compare salts with the same structure

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10
Q

How do you work out the number of valence electrons

A

number of e- in shell
+1 per bond
+1 if neg charge -1 if pos charge

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11
Q

How do you work out the geometry of an atom

A

-Draw lewis structure
-decide on atom
-count e-s
-use number of e- bairs, bonding pairs and lone pairs to determine geometry

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12
Q

What factors impact molecular geometry

A

-Lone pairs
-Electronegative groups
-Multiple bonds

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13
Q

How do lone pairs effect geometry

A

lone pairs occupy more space,
angle between bonding pairs compressed
lp;bp repulsion greater than bp;bp

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14
Q

How do electronegative groups effect the geometry

A

pulls the bps closer
angle H-C-H increases

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15
Q

how do multiple bonds effect the geometry

A

occupy more space than single bonds
the four electrons occupy more space so the bond angle is greater

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16
Q

whats special about trigonal bipyramidal

A

two distinct environments-2 axial and 3 equatorial
e-e 120, e-a 90, a-a 180

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17
Q

what are the limitations of vsepr

A

doesnt take into account stereochemically inactive lone pairs (bottom of periodic table lps occupy spherical s orbitals)
Cant use for radicals

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18
Q

What is the assumption in valence bond theory

A

bonds are located between pairs of atoms

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19
Q

what is hybridisation

A

sp3-hybrid orbitals
What does it look like?

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20
Q

what happens when there is more s character in a given bond

A

the bond is shorter due to the the s electrons being held closer to the nucleus

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21
Q

for resonance what needs to happen

A

the groups need to be conjugated, +M and -M on neighbouring atoms

22
Q

what resonance form is favoured

A

the negative charge on the most electronegative atom

23
Q

what is thermodynamics

A

how far a reaction will proceed, based on energies between starting and end material

24
Q

what is kinetics

A

how fast a reaction will proceed, governed by activation energy

25
Q

what is the bronsted lowry definition of of acids and bases

A

an acid is a substance which is a proton donor, a base is a substance that accepts a proton

26
Q

what is the lewis definition of acids and bases

A

an acid is a substance which is an electron pair acceptor and a base is a substance which is an electron pair donor

27
Q

What is the conjugate base (bronsted)

A

the species formed from the acid after the proton loss

28
Q

What is the conjugate acid (bronsted)

A

the species formed from the base after it has accepted a proton

29
Q

what is the equation for pKa

A

-log10ka

30
Q

What controls acidity (4)

A
  1. strength of the H-A bond
  2. Electronegativity of A
  3. Stabilisation of A- compared to HA, resonance
  4. the solvent
31
Q

how does the stability of the conjugate base increase

A

as the charge per oxygyen atom decreases
the negative charge is spread over a greater number of electronegative atoms

32
Q

what does a low pka mean

A

the stronger the acid and the better its ability to donate a pair of electrons or proton, it measures how completely an acid dissociates in an aqueous solutions

33
Q

the more stable the conjugate base

A

acidity increases

34
Q

the stronger the base..

A

the weaker the conjugate acid, therfore a lower ka and a higher pka

35
Q

ka =

A

conc of products/conc of acid

36
Q

kc =

A

conc of products^n/conc of reactants^n

37
Q

how do yuo differentiate very strong acids

A

appear to be same strength due to being completel dissociated (water good proton acceptor)
solvent levelling
use a solvent that is more difficult to protonate than water for example ehtanoic acid

38
Q

how dop you differnetiate between strong bases

A

same as acid with water
use a solvent like liquid ammonia

39
Q

what is amphiprotic

A

capable of donating and accepting a proton

40
Q

what is amphoretic

A

it is both an acid and a base

41
Q

what is kw

A

for water self ionising
kc=conc of products^n/conc of reactant^n
kw=conc of products

42
Q

pH=

A

-log10[H3O+]
the pH of water varies with temp

43
Q

when a reaction is endothermic

A

equilibrium moves to the right

44
Q

for a weak acid

A

[H3O+]=[A-]

45
Q

degree of dissociation

A

=[H3O+]/[HA].100

46
Q

Buffer

A

resist change in pH
made from weak acids and their conjugate bases or from weak bases and their conjugate acids eg Ch3COOH+CH3COONa or
NH3+NH4Cl

47
Q

buffer capacity

A

depends on conc of salt and acid used

48
Q

Henderson Hasselbach equation

A

pH=pka+log10[A-]/[HA]
ph of buffer will be close to pka of acid so can be tuned by cahanging A/HA

49
Q

Titration curve strong acid-base

A

equivalence point at pH 7

50
Q

titration curve weak acid-strong base

A

equivalence point>7

Chemistry sem 1 (3 decks)

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