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Higher Chemistry > Unit 1- rate of reaction and periodicity > Flashcards

Unit 1- rate of reaction and periodicity Flashcards

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1
Q

What 3 things must happen for a chemical reaction to occur?

A

Particles must collide with one another
Particles must collide with sufficient energy
Particles must collide with the correct geometry

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2
Q

What are the two basic ways reaction rates can be increased?

A

Increasing the number of collisions

Increasing the number of particles with the activation energy

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3
Q

How can the number of collisions be increased in a reaction

A 
Increasing...
Surface area
Concentration
Pressure 
Temperature
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4
Q

How can the number of particles with the activation energy be increased?

A

Increasing the temperature

Adding a catalyst

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5
Q

What is concentration

A

The number of particles in a given volume

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6
Q

Explain what happens when the concentration of reacts are increased in a chemical reaction

A

More collisions take place and therefore the reaction is faster due to more successful collisions

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7
Q

What is pressure?

A

How often the gas molecules collide with the walls of a container

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8
Q

How can pressure be increased?

A

Compressing the same number of particles into a smaller volume

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9
Q

How does increasing the pressure increase reaction rate?

A

More collisions take place and therefore there will be more successful collisions

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10
Q

What reacts faster powders or grains?

A

Powders

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11
Q

Why does a decrease in particle size increase the rate of a reaction?

A

There is a larger number of particles on the surface of a solid that are able to take part in collisions

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12
Q

What is temperature?

A

The average kinetic energy of the particles of a substance

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13
Q

Why does increasing temperature increase reaction rate?

A

The reaction particles will have a greater kinetic energy and so collisions between then are more likely to be successful

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14
Q

Increasing temperature means that more particles have…

A

The required activation energy

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15
Q

How do you measure the relative rate of a reaction?

A

1/time taken for the reaction to take place

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16
Q

What is the units for relative rate?

A

s-1

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17
Q

What is a potential energy diagram used for?

A

To show the energy pathway for a chemical reaction

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18
Q

What is enthalpy?

A

The measure of chemical potential energy contained in a substance

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19
Q

What is the symbol for enthalpy?

A

H

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20
Q

What is enthalpy change measured in?

Not one mole

A

kJ

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21
Q

What is enthalpy change measured in?

One mole of a substance

A

kJmol-1

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22
Q

What is the equation for enthalpy change?

A

Enthalpy of products minus enthalpy of reactants

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23
Q

What is an exothermic reaction?

A

A reaction where chemical potential energy is changed into heat energy and heat energy will be lost

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24
Q

What happens to the temperature in an exothermic reaction

A

It will increase

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25
Q

The value of Hp is lower than Hr for an exothermic reaction

True or false

A

True

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26
Q

Enthalpy change of an exothermic reaction is positive

True or false

A

False

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27
Q

What is an endothermic reaction?

A

A reaction where heat energy is taken in and changed into chemical potential energy

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28
Q

What happens to the temperature of an endothermic reaction?

A

It will decrease

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29
Q

The value of Hp is greater than Hr in an endothermic reaction
True or false

A

True

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30
Q

The enthalpy change for an endothermic reaction is positive

True or false

A

True

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31
Q

What is activation energy?

A

The energy required by the colliding molecules to form an activated complex

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32
Q

What is an activated complex?

A

An unstable intermediate with bonds within the reactant molecule beginning to break and new bonds forming to make products

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33
Q

What is the symbol for activation energy

A

Ea

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34
Q

Where is the activated complex represented by on a potential energy diagram

A

At the top of the activation barrier

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35
Q

A different activated complex is for in the reverse reaction than the forward reaction
True or false

A

False

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36
Q

What do energy distribution diagrams show?

A

How many particles are moving with each value of kinetic energy

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37
Q

How is the activation energy represented on an energy distribution diagram

A

A dashed line from the X axis

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38
Q

On an energy distribution diagram what represents the number of particles which have sufficient energy to react?

A

The area under the curve to the right of Ea

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39
Q

If the temperature of a reaction increases what happens to the number of particles with Ea?

A

Increases

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40
Q

What happens to a catalyst during a reaction?

A

The catalyst takes part in the reaction but is regenerated at the end of the reaction

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41
Q

What do catalyst provide?

A

An alternative reaction pathway with a lower activation energy

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42
Q

What does a catalyst do to the activation energy

A

Decreases it

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43
Q

What does a catalyst do to the energy distribution diagram?

A

Moves the activation energy line to the left

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44
Q

How are the elements in the periodic table arranged?

A

In order of increasing atomic number

45
Q

What are the vertical columns of the periodic table called?

A

Groups

46
Q

What are the horizontal rows in the periodic table called

A

Periods

47
Q

What do all the elements in one group have in common

A

Chemical properties

48
Q

What is group 0 called

A

Noble gases

49
Q

How do the noble gases naturally exist

A

Single, unattached atoms

50
Q

Describe the noble gases outer electron shell

A

Stable

51
Q

Name the monatomic gases among the first 20 elements

A

Helium
Neon
Argon

52
Q

Are the boiling and melting points of monatomic gases high or low

A

Low

53
Q

Why do monatomic gases have low mp and bp

A

They are easily separated by overcoming the weak forces of attraction between the atoms

54
Q

What are the forces between monatomic gases?

A

London dispersion forces

55
Q

Describe a temporary dipole

A

One side of an atom or molecule becomes slightly negative and slightly positive

56
Q

What will happen to adjacent atoms or molecule to a temporary dipole

A

Induced dipoles

57
Q

What are London dispersion forces a result of

A

The electrostatic attractions between temporary dipoles and induced dipole

58
Q

What determine the strength of LDF

A

The size of the molecule or atom

59
Q

The strength of LDF is proportional to the number of electrons in an atom or molecule
True or false

A

True

60
Q

Why does more electrons lead to stronger London dispersion forces?

A

More dipoles are established

61
Q

Do the boiling points increase or decrease going down group 0

A

Increase

62
Q

What other bonding is involved in the noble gases except LDF

A

There are none

63
Q

Do metals gain electrons easily

A

No they lose electrons easily

64
Q

What happens to the electrons in metallic ally bonded elements

A

They become delocalised

65
Q

What is the structure of metal in a solid state?

A

A lattice

66
Q

What is a metallic lattice made up of

A

Positive metal ions held together by a sea of delocalised electrons

67
Q

What are metallic bonds

A

Electrostatic attraction between the positive metal ions and the negative delocalised electrons

68
Q

The delocalised electrons in a metallic lattice cannot move

True or false

A

False

69
Q

Why are metals good conductors

A

The presence of delocalised electrons

70
Q

Do metals have low or high mp and bp

A

High

71
Q

Why do metals have high mp and bp

A

Metallic bonding is fairly strong

72
Q

What does the strength of metallic bonds depend on

A

The number of outer electrons

73
Q

What bonding generally exists between two non metals

A

Covalent bonds

74
Q

How are covalent bonds formed

A

The merging of half filled electron shells

75
Q

How are the atoms in a covalent bond held

A

By the electrostatic forces of attraction between positively charged nuclei and negatively charged shared electrons

76
Q

What are covalent molecular elements?

A

Groups of atoms held together by covalent bonds inside the molecule yet weak intermolecular forces between the molecules

77
Q

What are the covalent molecular structures in the first 20 elements

A 
Hydrogen
Nitrogen
Oxygen
Fluorine
Chlorine
Phosphorous (P4)
Sulphur (S8)
Carbon- fullerene
78
Q

Are the mp and bp of covalent molecular structure low or high

A

Low

79
Q

Why is the mp and bp of covalent molecular structure low

A

The weak LDF

80
Q

What do covalent network structures consist of?

A

A giant lattice of covalent my bonded atoms

81
Q

Name the elements in the first 20 elements in the periodic table which are covalent network elements

A

Boron
Silicon
Carbon- diamond or graphite

82
Q

Do covalent network elements have high or low mp and bp

A

Very high

83
Q

Why are the mp and bp of covalent networks very high

A

The covalent bonds which a very strong have to be broken at their melting and boiling points

84
Q

What is graphite

A

Pure carbon

85
Q

Why is graphite a good conductor of electricity

A

The layers of delocalised electrons

86
Q

Where are the LDF in graphite

A

Between the layers

87
Q

Describe the density, melting points and conduction of monatomic elements

A

Low density
Low melting point
No conduction

88
Q

Describe the density, melting point and conduction of covalent molecular elements

A

Low density
Low melting point
No conduction

89
Q

Describe the density, melting point and conduction of covalent network elements

A

Very high density
Very high melting point
Doesn’t conduct except graphite

90
Q

Describe the density, melting point and conduction of metallic elements

A

High density
High melting points
Does conduct

91
Q

What is covalent radius

A

Half the distance between the nuclei of two bonded atoms

92
Q

What happens to the covalent radius going down a group

A

Increases

93
Q

Why does the covalent radius increase going down a group

A

Electron shells increase

94
Q

Does the covalent radius increase or decrease going across a period

A

Decrease

95
Q

Why does covalent radius decrease going across a period

A

Increasing nuclear charge due to increased number of protons

96
Q

What is ionisation energy

A

The energy required to remove one mole of electrons from one mole of gaseous atoms of an element

97
Q

What is the general equation representing the first ionisation energy of carbon

A

C(g)—>C+(g) + e-

98
Q

What is the equation for the third ionisation energy of carbon

A

C2+(g) —> C3+(g) + e-

99
Q

Does the ionisation energy increase or decrease going down a group

A

Decrease

100
Q

Why does the ionisation energy decrease going down the group

A

More electron shells so the electron if further from the nucleus
Shielding effect

101
Q

Does the ionisation energy increase or decrease going across the period

A

Increase

102
Q

Why does the ionisation energy increase going across a period

A

Nuclear charge increases

103
Q

What is electronegativity

A

Measure of attraction an atom has for the electrons bonded

104
Q

What are the units for electronegativity

A

No units

105
Q

Does the electronegativity increase or decrease going down a group

A

Decrease

106
Q

Why does electronegativity decrease going down a group

A

Atomic size increases and so the shared electrons are further from the nucleus
Greater shielding

107
Q

Does the electronegativity increase or decrease going across a period

A

Increase

108
Q

Why does electronegativity increase going across a period

A

Nuclear charge is increasing due to the increase in protons

Higher Chemistry (3 decks)

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