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Chemistry A-level ♡ > Section 1 - Physical Chemistry > Flashcards

Section 1 - Physical Chemistry Flashcards

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1
Q

Which letter is used to represent the atomic number of an atom?

A

Z

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2
Q

What does the atomic number tell us about an element?

A

Atomic number = number of protons in an atom

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3
Q

What number represents mass number?

A

A

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4
Q

How is the mass number calculated?

A

mass number = number of protons + number of neutrons (total number of nucleons)

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5
Q

Define relative atomic mass

A

The average mass of all isotopes of an element compared to 1/12 the mass of an atom of Carbon 12(c12)

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6
Q

What are isotopes of an element?

A

Different forms of the same element, contain the same number of protons but different numbers of neutrons. they have the same chemical properties of the original element.

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7
Q

How many orbitals and electrons do these shells contain? a) 1s b) 2p c) 3s d) 3d e) 4s

A

a) 1s- 1 orbital, 2 electrons
b) 2p- 3 orbitals, 6 electrons
c) 3s- 1 orbital, 2 electrons
d) 3d-5 orbitals, 10 electrons
e) 4s- orbital, 2 electrons

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8
Q

Does 3d or 4s have a higher energy?

A

3d

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9
Q

What is an orbital?

A

a region around the nucleus that can hold up to 2 electrons

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10
Q

What would be the relationship between 2 electrons in the same orbital in terms of their spin?

A

have opposite spin as they repel each other as the charge of both electrons is negative

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11
Q

Explain why chromium does not fit the trend for electronic configuration

(electronic config the arrangement of electrons orbitals arounnd a nuc)

A

it only has one elctron in its 4s orbital before filling 3d.

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12
Q

Explain why copper does not fit the trend for electronic configuration.

A

it only has one electron in its 4s orbital before filling 3d

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13
Q

What are the two types of ionisation for a mass spectrometer? how do they differ?

A
  1. Electron impact : electron gun (hot wire filament with current through it emitting electrons) knocks off one electron from each particle to form 1+ molecular ions (these ions fragment)
  2. electrospray: sample dissolved in volatile solvent (e.g. water or methanol) and injected through a fine hypodermic nedle to give an aerosol. Needle attached to positive terminal of a high-voltage power supply and partiles gain a proton from the solvent as they leave the needle, producing XH+ ions (1= charge and a mass of mr +1). (ions rarely fragment).
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14
Q

When would you use the different of ionisation in a mass spec?

A
  1. Electron impact used for organic or inorganic molecules with a low formula mass
  2. electrospray used for substances with a higher molcule mass including biological molecules
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15
Q

Describe how a time of flight mass spectometer works

A

Acceleration - positive ions attracted to a negativley charged plate.
Ion drift - ions pass through hole in plate, form a beam with constant kinetic energy, travel along tube to detector. time of flight is therefore directily proportional to the square root of mass
Detection - positive ions pick up electrons, current flows, m/z value and time of flight recorded. largest current from most abundant ions.

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16
Q

Define first ionisation energy

A

the energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions

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17
Q

Define time-of-flight mass spectometery

A

Time-of-flight mass spectrometry (TOFMS) is a method of mass spectrometry in which an ion’s mass-to-charge ratio is determined by a time of flight measurement

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18
Q

What is the symbol for the amount of substace?

A

n

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19
Q

What is the unit used to measure the amount of substance?

A

mole

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20
Q

What does the avogadro constant represent?

A

Number of atoms per mole of the Carbon-12 isotope

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21
Q

How do you calculate the mass of one mole of the element?

A

mass of 1 mole = relative atomic mass in grams

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22
Q

How do you calculate moles when mass and molar mass are given?

A

Moles (mol) = mass(g) /molar mass (g mol -1)

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23
Q

State avogadro’s Law

A

Under the same temperature and pressure, one mole of any gas would occupy the same volume

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24
Q

How much volume does a gas occupy, at room temperature and pressure?

A

24 dm^3 or 24000^3

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25
Q

Define molar gas volume.

A

The volume of gas molecules per mole.

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26
Q

Why do different gas particles occypy the same volume?

A

The particles in each gas are very spread out, hence individual differences have no effect

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27
Q

How do you calculate moles when gas volume is given?

A

Moles (mol) = volume (dm^3)/24
or
Moles (mol) = volume (cm^3) / 24000

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28
Q

What are the ideal ways in which gases behave?

A
  1. they are in continous motion
  2. no intermolecular forces experienced
  3. exert pressure when they collide with each other or container
  4. no kinetic energy is lost in the collisions
  5. when temperature increases, kinetic energy of gases also increase
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29
Q

What is the ideal gas equation?

incl. words, symbols and units.

A

pV= nRT
pressure (Pa) x volume (m^3) = number of moles (mol) x gas constant (8.314 j mol-1) x temperature (k)

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30
Q

How many pascal is 1 atmospheric pressure equivalent to?

A

1 atm = 101325 Pa

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31
Q

How many kelvin is 0 C equivalne too?

A

273 K

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32
Q

What does concentration of a sulution mean?

A

It is the amount of solute dissolved in 1 dm^3 of solvent

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33
Q

How do you calculate moles when concentration and volume are given?

A

Moles (mol) = concentration (mol dm^-3) x volume (dm^3)

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34
Q

What is a standard solution?

A

a solution of known concentration

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35
Q

What are the steps to preparing a standard solution?

A
  1. weigh the solute using the weigh by difference method
  2. In a beaker dissolve the solute using the solvent
  3. pour the solution in a volumeteric flask
  4. rinse the beaker using the solution and add it to the flask
  5. add solvent to tjt flask carefully until it reaches the graduation lin
  6. mix the solution thorougly to ensure compleste mixing
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36
Q

What do the terms concentrated and dilute mean?

A

Concentrated - Large amount of soulute per dm^3 of solvent

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37
Q

What is a species in a chemical reaction?

A

Any particle that takes part in a reaction

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38
Q

What are the four common state symbols?

A
  1. Solids (s)
  2. Liquid (l)
  3. gaseous (g)
  4. aqueous (aq)
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39
Q

What is the percentage yield?

A

The efficiency of which reactants are converted into products

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40
Q

What are the reasons for not obtaining 100% yield (5)

A
  • reaction may be at equilibrium
  • the reactants may be impure
  • side reactions could happen
  • reactants or products may be left behind while transferring
  • loss of products during seperation and purification
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41
Q

How is percentage calculated?

A

Percentage yeild = (actual amount of product (mol) /theoretical amount of product (mol)) x 100

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42
Q

What does atom economy tell us about?

A

the proportion of desired products compared with all the products formed in the reaction

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43
Q

How is atom economy calculated?

A

Atom economy = (molecular mass of desired product / sum of the molecular masses of all products) x100

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44
Q

Does 100% yield mean 100% atom economy?

A

No, even if all the reactants are converted into products, not all products og the reaction will be the required products.

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45
Q

Which type of reaction has 100% atom economy?

A

Addition reaction. (two or more reaction are combined to form a product.

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46
Q

What is ionic bonding?

A

Strong electrostatic forces of attarction between oppositely charged ions held in a lattice

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47
Q

Give an example of an ionically bonded substance

A

NaCl- SOdium chloride - salt

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48
Q

Do ionically bonded substances have a high melting and boiling point?

A

Yeas. this is beacuse it takes alot of energy to break strong electrostatic forces of attraction between the oppositley charged ions

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49
Q

Do ionic compound conduct electricity?

A

Yes, when molten or when dissolved in an aqueous solutiom as the ions are free to move around and carry charge.

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50
Q

What is simple olecular covalent bonding?

A

Strong covalent bonds between atoms, weak van der waals forces of attraction betweeen molecules

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51
Q

Are there any lone electrons in simple covalent bonding?

A

No- all involved in bonding

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52
Q

Can simple molecular covalent molecules conduct electricity? why?

A

No- all electrons used in bonding and arent free to move

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53
Q

Do simple molecular substances have a high / low mp and bp?

A

Low - Weak van der waals forces of attraction between molecules that dont take much energy to overcome,( these are overcome rather ran covalent bonds)

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54
Q

Describe macromolecular covalent bonding

A

a lattice of many atoms held together by strong covalent bonds

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55
Q
A
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56
Q

Do substannces wit macromolecular covalent bonds have a high/low mpt and bpt? why?

A

they have high melting points and boiling points as it takes a lot of energy to overcome strong covalent bonds

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57
Q

Do substances with macromolecular covalent bonds conduct electricity?

A

Most don’t as all electrons are used in bonding

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58
Q

Describe the structure of diamond

A

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

59
Q

Describe the structure of graphite

A

Similar to diamond- macromolecular covalent - but each c atom is only bonded to 3 others, so it is in layers
Weak Van der Waals forces of attraction between layers mean they can slide over each other – soft, slippery
one elctron from each carbon is delocalised and can carry charge —- conducts electricity.

60
Q

Describe metallic bonding

A

Lattice of positive metal ions strongly attached to a sea of delocalised electrons. Layers can slide over each other - malleable

61
Q

Do mettalic compunds have high/ low boiling and melting points? why?

A

high as strong forces of attraction between positive metal ions and negativley charged sea of delocalised electrons

62
Q

Do metallic compounds conduct electricity? Why?

A

Yes as delocalised electrons can move throughout the metal to carry charge

63
Q

How does the strength of metallic bonds change across the periodic table? why?

A

Increases as higher melting and boiling points mean a higher charge on metal ions
and more delocalised electrons per ion.
stronger force of attractio n between them

64
Q

Define electronegativity

A

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

65
Q

What affects electronegativity

A

Nuclear charge
Atomic radius
Electron shielding

66
Q

What is the most electronegative element?

A

Fluorine (4.0 on Pauling’s scale) Has the largest nuclear charge for its electron shielding, small atomic radius.

67
Q

How do you get a nonpolar bond?

A

By having both bonding Elements have the same electronegativities

68
Q

When do you get a polar bond?

A

When bonding atoms have different electronegativities

69
Q

What is the strongest type of inter-molecular force?

A

Hydrogen bonding

70
Q

What is the weakest type of inter-molecular force?

A

Van der Waals forces

71
Q

Describe van der Waals’ forces of attraction.

A

the random movement of electrons creates temporary dipoles which induces a dipole in a neighbouring molecule therefore a temporary dipole-dipole attraction aka van der Wasls forces of attraction is made.

72
Q

Are Van der Waals forces stronger in smaller or larger molecules?

A

larger- more electrons

73
Q

Describe permanent dipole-dipole attraction.

A

Some molecules with polar bonds have permanent dipoles. this creates forces of attraction between those dipoles and those of neighbouring molecules.

74
Q

What conditions are needed for hydrogen bonding to occur?

A

O-H, N-H or F-H bond, lone pair of electrons on O, F,N because they are highly electronegative, H nucleus is left exposed
Strong force of attraction between H nucleus and lone pair of electrons on O, N, F

75
Q

Why is ice less dense than liquid water?

A

in liquid water, hydrogen bonds constantly break and reform as molecules move about.
In ice, the hydrogen bonds hold the molecules in fixed positions; this makes them slightly further apart than in liquid water

76
Q

What is a dative/co-ordinate covalent bond? when is it formed?

A

formed when an electron-deficient aton/ion accepts a lone pair of electrons from an atom/ion with a pair of lone electrons (not used in bonding)

77
Q

What does the shape of molecules depend on?

A
  1. Number of electrons in the valence shell of the central atom
  2. number of these electrons which are in bonded or lone pairs
78
Q

What does the electron pair repulsion theory state?

A

That electron pairs will take up positions as far away from each other as possible, to minimise the repulsive forces between them

79
Q

Which experience the most repulsion?
LP-LP, LP-BP or BP-BP

A

LP-LP strongest repulsion
LP-BP medium repulsion
BP-BP weakest repulsion

80
Q

What is the shape, diagram and bond angle is a shape with two bonded pairs and 0 lone pairs?

A

linear shape, 180-degree bond angle

81
Q

What is the shape, diagram, and bond angle of a shape with 3 bonding pairs and 0 lone pairs?

A

Trigonal planar 120

82
Q

What is the shape diagram and bond angle in a shape with 4 bonded pairs and 0 lone pairs?

A

tetrahedral 109.5

83
Q

What is the shape diagram and bond angle in a shape with 5 bonded pairs and 0 lone pairs?

A

Trigonal bipyramid 90 and 120

84
Q

What is the shape diagram and bond angle in a shape with 6 bonded pairs and 0 lone pairs?

A

Octahedral 90 degrees

85
Q

What energy change is breaking bonds associated with?

A

Energy is taken in to break bonds –> endothermic reaction

86
Q

What energy change is making bonds associated with?

A

Energy is released to make bonds –> exothermic

87
Q

What are some uses of thermochemistry?

A
  1. measuring and comparing the energy values of fuels.
  2. calculating the energy requirements for industrial processes
  3. Working out the theoretical amount of energy released/taken in in a reaction
  4. predicting if a reaction will take place or not.
88
Q

What is an endothermic reaction?

A

one with an overall positive enthalpy change (=^H) or when energy in breaking bonds> energy out breaking bonds

89
Q

What is an exothermic reaction?

A

one with an overall negative enthalpy energy change. (-^H) energy in breaking bonds< energy out breaking bonds

90
Q

If a reversible reaction is endothermic one way, what type of reaction is the other way?

A

exothermic

91
Q

Give 2 examples of exothermic reactions.

A

Combustion of fuels
neutralisation

92
Q

Give an example of an endothermic reaction

A

thermal decomposition

93
Q

Define enthalpy change; what symbol is used to represent it?

A

Energy change of a system at constant pressure
represented by ^H

94
Q

What are the standard conditions?

A

100kPa / 1atm pressure
298K/25 degrees C temp.

95
Q

What does “in standard state” mean?

A

the state an element/compound exists at in standard conditions

96
Q

Draw an enthalpy change diagram for an endothermic reaction and one for an exothermic reaction.

A
97
Q

Give an example of an equation which represents the standard enthalpy of formation

A

H^2 (g) + 1/2 O^2 (G) –> H20 (l)

98
Q

Define standard enthalpy of combustion

A

The enthalpy change when one mole of a substance is burnt completely in oxygen in standard conditions (100kPa, 298K), with reactants and products in their standard states lo

99
Q

Give an example of an equation which represents standard enthalpy of combustion.

A

C (s) +o^2 (g) —> CO^2 (g)

100
Q

what is the difference between heat and temperature?

A

heat is the sum of all particles’s energy, therefore it is affected by the amount of substance; temperature is related to the mean kinetic energy of particles in a system, so is independent of the number of particles present.

101
Q

How can you calculate enthalpy change from experimental data?

A

usee the equation Q+ mc^T where m is the mass of the substance being heated (usually water) c, is the specific heat capacity of that substance and ^T is the change in temperature.

102
Q

Describe and explain an accurate simple calorimeter

A

To make it more accurate, add draught screens at the sides, and add a lid on top of the beaker. do this in order to insulate and reduce heat lost to the surroundings

103
Q

What is a flame calorimeter? how does it differ from a simple calorimeter?

A

Reduces heat lost to the surroundings to give more accurate results: has a spiral chimney made of copper, an enclosed flame and the fuel is burnt in pure oxygen, not air.

104
Q

How would you measure the enthalpy change for a reaction occurring in (aq)

A

use an expanded polystyrene cup as a calorimeter (good insulator so reduced heat loss). heat is generated in the solution; measure this temperature change. and take the heat capacity of the solution to be 4.18 and the density of the solution to be 1gcm-3

105
Q

What can you use to make experimental determination of enthalpy change of reaction more accurate?

A

cooling curves

106
Q

What is Hess’s law?

A

States that enthalpy change for a reaction is the same regardless of the route taken

107
Q

What is the enthalpy of an element?

A

the enthalpy of all elements in their standard states is defined as 0

108
Q

Define bond dissociation enthalpy.

A

the enthalpy change required to break a covalent bond, with all the species in the gaseous state; differs for the same bond in different molecules.

109
Q

Define mean bond enthalpy.

A

Average value (across different chemical environments) for the bond dissociation enthalpy of a given bond

110
Q

Why may experimental methods of enthalpy determination not be very accurate?

A
  1. heat is lost to the surroundings
  2. not in standard conditions
  3. Reaction may not go to completion
111
Q

Why will using bond enthalpies not be as accurate as using standard enthalpy of combustion/ formation?

A

Bond enthalpies are a mean for the same bond across different molecules; standard enthalpy of combustion and formation apply to just that molecule, therefore they are more accurate.

112
Q

What must particles do in order to react?

A

Collide with sufficient energy (activation energy) and the correct orientation

113
Q

Do most collisions result in a reaction?

A

No

114
Q

Define Activation energy.

A

The minimum energy that particles must collide with for a reaction to occur

115
Q

Describe a labelled Maxwell curve.

A
116
Q

What is the effect of increasing temperature on the rate of a reaction?

A

An increasing temperature means an increased reaction rate due to a much higher proportion of particles having energy greater than the activation energy. this leads to many more successful collisions per second and a higher rate of collisions

117
Q

What is the effect of increasing concentration/pressure on the rate of reaction?

A

Increased conc/pressure means more particles in a given volume, more frequent collisions, and an increased rate of successful collisions.

118
Q

What is a catalyst?

A

A substance which increases the rate of reaction but is not used up in the process.

119
Q

How do catalysts work and how do they increase the rate of reaction?

A

Provide an alternative reaction pathway (one with a lower activation energy)
lowers the activation energy, so more particles have energy> activation energy, so more frequent successful collisions, so an increased reaction rate.

120
Q

Define the term dynamic equilibrium.

A

When the rate of the forward reaction is equal to the rate of the reverse reaction. (hence, the concentrations of reactant and product do not change)

121
Q

What essential conditions are needed for an equilibrium mixture?

A
  • A closed system
  • macroscopic properties do not change with time
122
Q

What is Le Chatelier’s Principle?

A

If a systtem at equilibrium is distrurbed, the equilibrium moves in the direction that tends to reduce the disturbance

123
Q

What is a compromise pressure?

A

When the pressure is increased in a reaction to increase the rate of reaction but also produces a slightly lower yeild of desired product.

124
Q

What effect does a catalyst have on the position of equilibrium?

A

No effect beacuse catalyst affects the rate of the forward and backward reaction equally

125
Q

What condition affects the value of K^c

A

Temperature

126
Q

What type of system is K^c relevant for?

A

Homogeneous systems in equilibrium

127
Q

What does K^c being greater or lesser than 1 suggest for the position of equlibrium?

A

greater than 1= over to the right
less than1= Over to the left

128
Q

What does decreasing the temperature in an endothermic reaction have on K^c?

A

K^c decreases

129
Q

What effect does incresing the temperature in an endothermic reaction have on K^c?

A

increases

130
Q

What effect does decreasing the temperature in an exothermic reaction have on K^c?

A

increases

131
Q

What effect does increasing the temperature in an exothermic reaction have on K^c?

A

decreases

132
Q

What is oxidation?

A
  1. the loss of electrons
  2. the gainof oxygen or any electronegative element
  3. loss of hydrogen or anmy electropositive element
133
Q

What is reduction?

A
  1. The gain of electrons
  2. the loss of oxygen or any electronegative element
  3. gain of hydrogen or any electropositive element
134
Q

What is an oxidising agent?

A

Species that gains electrons

135
Q

What is a reducing agent?

A

Species that lose electrons

136
Q

Define oxidation state

A

A number which represents the number of electrons lost or gained by an atom of that element in the compund

137
Q

What is the oxidation state of Oxygen in OF^2?

A

[O] = +2

138
Q

What is the oxidation state of hydrogen in KH?

A

[H] = -1

139
Q

What is the oxidation state of chlorine in NaCIO?

A

[CL] = +1

140
Q

Defiine the tern term disproportionation?

A

Where in a redox reaction, the oxidation states of atoms of the same element, increases for some atoms, whereas decrease for some atoms

141
Q

What is the oxidation state of nitrogen in ammonia?

A

[N] = -3

142
Q

What is the oxidation state of arsenic in AsO^4-3?

A

[As] =+5

143
Q

What is the oxidation state of iron in K^4 Fe (CN)^6?

A

[Fe] =+2

144
Q

What happens in a redox reaction?

A

Electrons are transferred from one species (element) to another.
One element is oxidised whilst another is reduced.

Chemistry A-level ♡ (4 decks)

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