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full custy notes Flashcards

1
Q

definition of a standard solution

A

a standard solution is one of known concentration

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2
Q

how can a standard solution can be prepared

A

accurately weigh out the mass of a solute by weighing by difference, transfer the solute into a beaker and add deionised water.
to dissolve the solute.
then pour the mixture into a standard flask , using a funnel
then rinse the beaker and funnel with deionised water, using a pipette make the solution up to the graduation mark with deionised water, then invert the flask several times

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3
Q

characteristics of a primary solution

A

extremely high purity

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4
Q

examples of suitable primary standards

A

sodium carbonare

sodium chloride

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5
Q

draw a calculation graph

A

absorbance at side and concentration at the bottom

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6
Q

what is atomic emission

A

atomic emission absorption are used to identify and quantify elements present in a sample. this is done by exciting electrons and producing absorption/emission

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7
Q

what is empirical formula

A

empirical formula is the simplest ratio of atoms in a compound

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8
Q

what is equilibrium constant

A

the equilibrium constant has the symbol k, (k has no units). the general equation for k is
aA + bB ->

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9
Q

difference between homogeneous equilibrium and a heterogeneous mixture

A

homogeneous equi: all species in equation are same state

heterogeneous equi: species in equation are different states

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10
Q

how do you write an expression for k when it is a heterogeneous equilibrium

A

when writing an expression for k in a heterogenous equilibrium, pure solids and liquids are emitted as their concentration is taken as constant and given value 1

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11
Q

what does the value of k tell us about the position of equilibrium

A

if k=1 neither products/reactants are favoured k>1 => products are favoured, k<1 => reactants are favoured

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12
Q

what effect does pressure have on k

A

this will change equilibrium position, the value of k does not change

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13
Q

what effect does a catalyst have on k

A

not change equilibrium position. value of k does not change

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14
Q

what effect does temp have on k

A
  • if endothermic, an increase in temp products, and product/ reactant ratio increases. therefore k increases
  • if exothermic, increase in temperature favours reactants and so ratio product/reactant decreases. therefore k decreases
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15
Q

what effect does concentration have on k

A

it will change equilibrium position, however value of k does not change

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16
Q

equation for parts per million

A

ppm=grams of solution x 1,000,000

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17
Q

what is 1ppm equal to

A

1ppm=1mgkg-1.

1ppm=1mgl-1

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18
Q

be able to draw skeletal formulas

A

.

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19
Q

rough procedure for a back titration

A

a back titration allows the concentration of an unknown solution to be determined by reacting it with a known excess of a reagent. the quantity of the excess reagent is determined by titration of/with a second reagent

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20
Q

why is a back titration carried out

A

a back titration is used for substances that are not a primary standard, therefore a standard solution cannot be prepared

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21
Q

what is the formula for calculating dilution factor

A

df= final volume/initial volume

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22
Q

what is the procedure for diluting a solution

A

calculate the dilution factor, the initial volume required and final volume. then add using a pipette, the required volume of solution to a standard flask of required volume. then make the solution up to the graduation mark by using deionised water and a pipette.

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23
Q

what are drugs - medicines

A

drugs are designed as substances that can alter the biochemical processes in the body medicines are those drugs that have a beneficial effect

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24
Q

different classifications of medicines

A

most medicines can be defined as agonist or antagonist according to the response they trigger when bound to a receptor

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25
Q

what’s an agonist

A

an agonist mimics the natural compound and binds to the receptor molecule to produce a response similar to the natural active compound

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26
Q

what’s an antagonist

A

an antagonist prevents the natural compound from binding to the receptor, and blocks the natural response from occurring

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27
Q

what is the section of a drug that binds to a protein receptor

A

the section of a molecule that binds to a protein receptor is called the pharmacophore

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28
Q

what are amines

A

amines are nitrogen containing organic compounds derived from ammonia in which one or more hydrogen atoms have been replaced by alkyl groups

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29
Q

typical shape of amines

A

pyramidal shape, because a lone pair in place of bonding pair, which exerts a stronger force, bond angle is 107 degrees between

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30
Q

how are they classified

A
  • primary amines have one r group attached to nitrogen atom
  • secondary amines have two r groups attached to nitrogen atoms
  • tertiary amines have 3 r groups attached to nitrogen atom
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31
Q

rules for naming amines

A

practice some

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32
Q

what is the skeletal structure for phenyl group

A

draw

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33
Q

what do amines react with

A

primary and secondary amines contain polar n-h bond. so have H bonding between molecule. no such bond occurs in tertiary because no H bond directly with nitrogen. p + s have high bp whereas tertiary has lower bp

  • amines with lower mass are soluble in water because they can form H bonds (including tertiary)
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34
Q

general structure of ethers

A

structure`; r-o-r, where r is alkyl group. an ether can be regarded as an alkane with an alkoxy group attached

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35
Q

rules for naming ethers

A

congest carbon chain gives parent name. ‘oxy’ also used instead.

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36
Q

physical properties of ethers

A

low bp because no h bonds. they can join h bond with water molecules, ie soluble in water

ethers are volatile and highly flammable
they are used as solvents. being volatile there solvents are removed by distillation

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37
Q

what is ems

A

electromagnetic radiation includes x rays and tv signals, different types of ems make up the ems

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38
Q

what produces ems waves

A

waves are produced by electrically charged particles

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39
Q

what are photons

A

electromagnetic radiation can be absorbed, when this occurs electromagnetic radiation behaves more like a stream of particles than as a wave. these particles caked photons. therefore say that electromagnetic raduatuin has a dual nature; wave motion and streams of photons

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40
Q

fromula to calc energy of 1 photon

A

e=hf

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41
Q

what is atomic process that produces atomic emission spectrum

A

when an atom gains energy it gets promoted to a higher energy level. When the excited electron drops back down to the lower energy level a photon is emitted.

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42
Q

Definition of transition metal

A

A transition metal has a partially filled d-sub shell in at least one of its valencies, ie when it is an ion

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43
Q

Why are zn and sc not considered a transition metal

A

Sc has an empty 3D orbital so doesn’t fit the tm definition

Zn has a full d orbital so doesn’t fit the tm definition

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44
Q

Electron configuration within a trans metal

A

(Fe) => [AR] 4s3 3d6.
As there is special stability, associated with half-filled/ completed filled d orbitals when transition metals atoms form ions electrons form the 4s orbitals are lost first

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45
Q

Oxidation state of a transition metal

A

Ox state is a change on an ion. TM’s show variable valency. Ie ionisable oxidation states/numbers

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46
Q

The preferred ox state depends on the stability of the ion

A

.

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47
Q

Why is Fe3+ the preferred ox state of iron

A

Fe3+ is the most stable as it is half filled

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48
Q

Rules for determining oxidation number of a trans metal

A
  • all free elements have an ox number = 0
  • for montomic ions, the ox number is the same as the charge on the ion
  • in compounds oxygen has an oxidation number of 2
  • hydrogen has an oxidation number of …
  • in polyatomic ions the sun of all the oxidation number is equal to the overall charge of the ion
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49
Q

What is oxidation / reduction

A

Oxidation is an increase I. Oxidation number

Reduction is a decrease in oxidation number

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50
Q

What compounds tend to be ox/reduce agents

A

Compounds containing metals high oxidation states tend to be good oxidising agents as rhe ions are easily reduced to lower oxidation states, compounds containing metals in low oxidation states tend to be reducing agents

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51
Q

What is a trans metal complex

A

A TM complex consists of a central metal ion surrounded by ligands, the metal ion is positive and acts as an electrophile

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52
Q

What is a Ligand

A

Ligands are negative ions with one or more lone pair of electrons that they can donate to the central metal ion, forming dative covalent bonds. A dative covalent bond is one in which both electrons in a bond are donated by one of the atoms.

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53
Q

What are the most common types of ligands

A

H20 - aqua
Nh3 - ammine (double m)
Fluorine - Flurido
Chlorine - chlorido

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54
Q

Different types of ligands

A

Monodentate ligands attach to the TM at one point. (Ie donate one pair of electrons)
A bidentate attaches at two points
Hexadentate at 6

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55
Q

Formula for a TM complex

A

Practice drawing

56
Q

Rules for naming a TM metal

A
  • number of ligands
  • name ligand (if more than one then alphabetical order)
  • TM
  • oxidation state of TM
57
Q

Practice negative TM complexes

A

Sound but x

58
Q

What is the coordination number

A

The number of bonds formed to the TM by ligands is called the coordination number, TMs commonly have a coordination number of 2,4,6

59
Q

What causes a line in the emission spectrum

A

An exited electron returns to ground state, emitting energy difference as visible light of a specific wavelength

60
Q

Why do the lines converge as they reach the continuum

A

The energy gaps between energy levels decrease with increasing energy. Ie the higher energy levels get closer and closer together

61
Q

what does the shape of a tm depend on

A

the shape depends on the coordination number

62
Q

why d orbitals in a tm are no longer degenerate

A

in TM complexes the ligands approach the central metal ion along the x,y,z axis. the electrons in d-orbitals if the metal ion are repelled by the electrons of the approaching ligands, there d-orbitals therefore have higher energy then the d-orbitals that lie between axes. the d-orbitals are no longer degenerate. this is known as the splitting of d-orbitals

63
Q

what are strong/weak field ligands

A

strong field ligands are ligands which cause a large difference in energy between the d-orbitals, weak field ligands cause a small difference in energy between d-orbitals (ie orbitals are split less)

64
Q

what is the spectrochemical series

A

ligands can be placed in order of their ability to split d-orbitals, this is the electrochemical series

65
Q

why do TM absorb light

A

light is absorbed when electrons in a lower d-orbital are promoted to a d-orbital of higher energy. if light of one colour is absorbed, the complimentary colour will be observed

66
Q

explain why TM are used as catalysts

A

TMs are used as catalysts because unpaired d electrons or unfilled d orbitals allows intermediate complexes to occur. twos weal’s the covalent bonds inside the reactant molecules, this can provide reaction pathways with lower EA. another reaction is because TM have variable oxidation states, this allows TM to provide an alternative reaction pathway with lower Ea

67
Q

what is a homogeneous/hetergeneous catalyst

A

homogeneous catalysts are in the same physical state as the reactants,
the heterogeneous catalysts are in a different physical states to reactants

68
Q

what is the valency shell electron pair Repulsion rule

A

VSEPR
states that a molecule will adapt the shape that results in the minimum repulsion between the valency electrons. bonds space out as far as possible from each other to give minimum repulsion forces.

69
Q

what is the hierarchy of repulsion between electron pairs

A

LP:LP>LP:BP>BP:BP

70
Q

what are the rules when working out the shape of a molecule that has no lone pairs

A
  • write formula
  • workout how many valency electrons the central atom and other atoms contribute to bonding
  • divide by 2 to get the number of bonding pairs
  • decide on the basic shape of the molecule.
71
Q

draw a table showing different shapes of molecules

A

memorise table

72
Q

what happens to the shape of molecules when there are lone pairs.

A

when lone pairs are inverted, the basic shapes are modified because the LP. has greater repulsion than the BP. where all the positions are not equal the LP goes to the site with the least repulsion, ie in the trigonal bipyrimdal this is the equational position. when there is more than one LP they try to get as far apart as possible from each other.

73
Q

when calculating PH, if its sulfuroc acid you have to divide your answer by two as sulphuric acid is dibasic.
h2so4

(2 hydrogens)

A

.

74
Q

calcium hydroxide formula ca(oh)2

A

for calcium hydroxide if ph u double the concentration as oh is 2 moles worth

75
Q

optical isomer

A

non-superimposable mirror images of each other

76
Q

In the reaction of but-1-yne with hydrogen, but-1-ene is formed. Explain why but-1-ene has no geometric isomers.

A

swapping any of the groups on the C=C results in the same structure.

77
Q

State how transition metals can act as catalysts.

A

empty/half-filled/incomplete d orbitals/subshell

78
Q

if it says binds to a receptor then its a pharmacophore

A

.

79
Q

if delta h/s/g has a dot it means standard conditions and so the temperature is deemed to be 298k

A

.

80
Q

What is standard enthalpy of combustion

A

Standard enthalpy of formation, H, is defined as the enthalpy change involved when one mole of a substance is formed from its elements in their standard states. Standard state of a substance is its most stable form at a pressure of 1 atom and a temp of 298k

81
Q

How can standard enthalpy of formation be used to calculate the enthalpy change for a reaction

A

Delta H= products - reactants

82
Q

What is entropy

A

Energy of a substance is a measure of the amount of disorder within that system, the larger the entropy the greater the amount of disorder. The symbol is s. Units KJ mol-1

83
Q

Solid,liquid, gas (which has highest entropy)

A

Gas highest to solid lowest

84
Q

Effect of temp on entropy

A

Higher temp means a higher degree of disorder (higher entropy) at the melting/boiling point of a substance there is a large increase in entropy

85
Q

What effect does an exothermic reaction have on the entropy of surroundings

A

Exothermic increases the entropy of surroundings as heat energy released

86
Q

What effect does an endothermic reaction have on the entropy of surroundings

A

Endothermic decreases entropy of surroundings heat energy released

87
Q

What is standard entropy of a substance

A

S, is the energy of 1 mol of the substance at temp 298K

88
Q

Third law of thermodynamics how is standard entropy calculated

A

The entropy of a substance (perfect crystal) at 0K is zero, because particles in a solid are no longer interacting at a perfectly absorbed 0K.

89
Q

What is a feasible reaction

A

Delta s= products-reactants

90
Q

What is the standard free energy change

A

A feasible reaction is a reaction that tends towards the products rather than the reactants

91
Q

What can be said about the reaction if the change in energy between reactants and products is negative

A

2nd law states that for a reaction to be feasible, total entropy for a reaction system and the surroundings must be positive for a spontaneous reaction, the total entropy and surroundings always increases

92
Q

How can degrees be converted to celsius

A

To convert degrees to kelvin, add 273

93
Q

Explain formation of molecular orbitals

A

In atoms electrons occupy atomic orbitals, electrons in molecules occupy molecular orbitals. Molecular orbitals are generated by combining atomic orbitals. The number of orbitals formed is equal to the number of atomic orbitals that combine. Each molecular orbital can hold two electrons.

94
Q

What are bonding molecular orbitals/antibonding molecular orbitals

A

One of the molecular orbitals is law and energy than either of the Tomich orbitals that combined to produce it, this is called a bonding molecular orbitals. The other molecular orbital is known as an anti bonding molecular orbital and is of higher energy than either of the atomic orbitals that combined to produce it.

95
Q

Difference between the bonding molecular orbital is polar/non-polar molecules

A

In a nonpolar molecule, the molecular orbital will be symmetrical around the two atoms. In a polar molecule, the molecular orbital will be asymmetric around the two atoms.

96
Q

Sigma bonds and their formation

A

Molecular orbital is formed by an Overlap of (atomic) orbitals along the axis of the bonds. I.e. a covalent bond, called a sigma bond. This is usually referred to as an end on overlap.

97
Q

Pi bonds

A

To parallel P atomic orbitals that are perpendicular to the axis of the bond can overlap laterally or side on to form a pi bond. The overlap of atomic orbitals is much less effective than the end on overlap. Pie bonds are weaker than Sigma bonds.

98
Q

What is hybridisation of orbitals

A

Hybridisation is the process of mixing atomic orbitals within an atom to generate a set of new atomic orbitals called hybrid orbitals. Which are degenerate

99
Q

Hybridisation of alkanes

A

In alkanes the four sp3 orbitals on each carbon atom will overlap and end on with four other orbitals, i.e. then the hydrogen ___ orbitals and one sp3 orbital on the other carbon atom. Four sigma bonds will be formed and they will adapt a tetrahedral arrangement.

100
Q

Hybridisation of alkenes

A

In alkenes, the 3 sp2 orbitals adapt a trigonal planar arrangement. In Ethene each carbon atom uses its three sp2 orbitals two form Sigma bonds with two hydrogen atoms and with other carbon. The unhybridized 2p orbital left on the carbon atoms overlaps the side to form a pi bond.

101
Q

Hybridisation of alkynes

A

In alkynes the 2 sp2 orbitals in each carbon form sigma bonds with the other carbon atom. The unhybridized 2p orbitals overlap side on to form pi bonds

102
Q

Hybridisation of benzene

A

In benzene, c6h6, each carbon atom is sp2 hybridised and the 3 half-filled sp2 orbitals form sigma bonds with a hydrogen aion and the two neighbouring carbon atoms. This leaves an electron occupying a p-orbital on each carbon atom. Each of there p-orbitals overlap side on with p orbitals on neighbouring carbon atoms, a pi electron bond is formed

103
Q

What is a chromophore

A

A chromophore is a group of atoms within a molecule which is replicable for absorption of light. Chromophores Exist in molecules, with conjugated system brackets attract double bonds. Delocalised electrons between atoms are conjugate system has alternating sigma and pi bonds

104
Q

Why some organic molecules appear coloured

A

Absorption of electromagnetic energy can cause electrons to be parallel from the highest occupied molecular orbital ‘homo’ to the coho. If the wavelength of light absorbed lies in the ems then the color observed will be complementary to that absorbed

105
Q

Why most organic molecules are colourless

A

Most organic molecules are colourless as the gap between the homo and lumo is large, this means that light from uv region is absorbed and so molecule appears colourless

106
Q

What happens to the frequency of light absorbed when the conjugated system contains more atoms?

A

If there are more atoms in the conjugated system then there is a smaller energy gap between homo/lumo. Therefore lower frequency and lower energy is absorbed.

107
Q

Geometric isomers:
 can occur when there is restricted rotation around a carbon-carbon double bond or a carbon-carbon single bond in a cyclic compound
 must have two different groups attached to each of the carbon atoms that make up the bond with restricted rotation
 can be labelled cis or trans according to whether the substituent groups are on the same side (cis) or on different sides (trans) of the bond with restricted rotation
 have differences in physical properties, such as melting point and boiling point
 can have differences in chemical properties

A

.

108
Q

The filling of the d orbitals follows the aufbau principle, with the exception of chromium and copper atoms.

A

.

109
Q

Oxidation can be defined as an increase in oxidation number. Reduction can be considered as a decrease in oxidation number.

A

.

110
Q

for chromium and copper do not include the 4s orbital

A

.

111
Q

what is an isomer

A

An isomer is a molecule with the same molecular formula but different structural formula

112
Q

What is a stereoisomers

A

A stereoisomer is when the order of bonding in each atom is the same but the spatial arrangement of the atom is different in each bond

113
Q

What are geometric isomers

A

A geometric isomer occurs when the arrangement of the atom is different in each isomer

114
Q

Under what circumstances do geometric isomers occur

A

Occur when there is rotation around a carbon to carbon double bond, also there must be two different groups attached to each of the carbon atoms that make up the bond

115
Q

What is meant by cis and trans

A

Cis is groups on the sdame side of the double bond, trans is groups on opposite side of the double bond

116
Q

How do properties of geometric isomers differ

A

Geometric isomers can have different physical properties

117
Q

What are optical isomers

A

They contain the same number and kinds of atoms and bonds, they are non-super imposable mirror images

118
Q

When do optical isomers occur

A

When four different groups are arranged tetrically around a central carbon atom (chiral carbon)

119
Q

How do properties of optical isomers occur

A

Identical but on light

120
Q

Effect of enantiomers on polarise light

A

One enantiomer will rotate light in one direction and the other enantiomer in the opposite direction by the same difference. as there is an equal amount of each enantiomer, the rotation would cancel

121
Q

What is a racemic mixture and why are they described as being optically inactive

A

A racemic mixture is an equal mixture of enantiomers, of a chiral molecule

122
Q

how does mass spectroscopy work

A
  • a small sample of an organic-compound is bombarded by high-energy electrons
  • this removes electrons from the organic molecule generating positively charged, molecular ions known as parent ions
  • these molecular ions break into smaller positively charged ion fragments
123
Q

State what is meant by a dative covalent bond.

A

Both electrons come from the same atom

124
Q

What is infrared spectroscopy used for

A

Its used to identify specific functional groups in organic molecules

125
Q

Explain how infrared spectroscopy works

A

Infrared spectroscopy intakes infrared at organic molecules which causes their bonds to vibrate in different ways. The wavelengths which are absorbed depend on the type of chemical bondand the atoms at the end of these bonds

126
Q

What is the general rule regarding the weight of atoms and bond strength

A

Lighter atoms are converted by stronger bonds (higher energy radiation absorbed), heavier atoms are connected by weaker bonds (lower energy radiation absorbed)

127
Q

What is nass spectroscopy used for

A

Mass spectroscopy is used to determine the accurate molecular mass and structural features of a compound

128
Q

How does mass spectroscopy work

A

A small sample of an organic compound is bombarded by high energy electrons. This removes electrons from the organic molecule generating positively charged molecular ions known as parent ions. These molecular ions then break into smaller positively charged ion fragments

129
Q

Explain how proton nmr spectroscopy works

A

Nuclei of atoms behave like tiny magnets and in a strong magnetic field some align with the field (lower energy) whilst the rest align against it (higher energy). The absorption of radiation in the radio frequency of the electromagnetic spectrum causes the 1h nuclei to flip from the lower to higher energy alignment. As they fall back from higher to lower energy alignment emitted radiation is detected and plotted on a spectrum

130
Q

How are proton environments identified

A

The fragments

131
Q

upper case or lower case k for equilibrium

A

upper (capital K for equilbrium

132
Q

upper or lower case k for rate constant

A

lower case k for rate

133
Q

vacuum filtration can be used to speed up the seperation of a filtrate

A

.

134
Q

why heat under reflux?

A

to prevent vapours escaping

135
Q

Explain in detail why vitamin A appears yellow, whereas β-carotene appears orange.

A

Beta-carotene has greater conjugation so the HOMO-LUMO gap is smaller (1), light of a higher wavelength (lower energy) is absorbed (1), colour we see is the opposite of this so orange (1)

136
Q

Explain fully how colour arises in these dye molecules.

A

Electrons move from HOMO to LUMO. (1)

Absorption of light (from the visible part of the spectrum) means that light of the complementary colour is seen.

137
Q

Explain how ligands bond to metal ions to form complexes.

A

Ligands) donate (lone/non-bonding) pairs of electrons (to the metal ion)

Advanced Chemistr (32 decks)

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