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Flashcards in Module 3 Deck (86):
1

What is the first ionisation energy?

The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions

2

What are the factors affecting ionisation energy?

Atomic radius:
• the greater the distance between the nucleus and the outer electrons the less the nuclear attraction

Nuclear charge:
• the more proton there are in the nucleus of an atom the greater the attraction between the nucleus and the outer electrons

Electron shielding:
• inner shell electrons repel outer shell electrons

3

What is the second ionisation energy?

The energy required to remove one electron from one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions

4

Trends in first ionisation energies

General increase across each period

Sharp decrease between the end of one period and the start of the next period

Decrease down a group

5

Trends across a period

Nuclear charge increases

Similar shielding

Nuclear attraction increases

Atomic radius decreases

First ionisation energy increases

6

What is metallic bonding?

The strong electrostatic attraction between actions and delocalised electrons

7

What happens in metallic bonding?

Each atom has donated its outershell electrons to a shared pool of electrons which are delocalised.

The cations left behind consist of the nucleus and the inner electron shells of the metal atoms.

8

Properties of metals

Strong metallic bonds

High electrical conductivity

High melting and boiling points

Insoluble

9

What are giant covalent lattices?

Many billions of atoms held together by a network of strong covalent bonds

10

What is the bond angle in a giant covalent lattice?

109.5

11

Properties of giant covalent lattices

High melting and boiling points

Insoluble in almost all solvents

Only graphene and graphite are able to conduct electricity

12

What is the periodic trend in melting points?

Across periods:
• melting point increases from group 1 to group 14
• sharp decrease in melting point between group 14 to 15
• comparatively low melting points from group 15 to 18

13

What is a reducing agent?

An element that has reduced another species and has been oxidised itself

14

Are group 2 metals oxidising agents?

No. They are reducing agents

15

What is formed when a group 2 element reacts with oxygen?

A metal oxide with the general formula MO

16

What is formed when a group 2 element reacts with water?

An alkaline hydroxide, with the general formula M(OH)2, and hydrogen gas

17

Metal + acid =

Salt + hydrogen

18

What is the reactivity trend down group 2?

Reactivity increases down the group

19

What is formed when a group 2 oxide reacts with water?

Hydroxide ions are released forming alkaline solutions of the metal hydroxide

20

What is the trend in solubility of hydroxides in water?

Increases down the group

The resulting solutions contain more OH- ions and are more alkaline

21

What can group 2 compounds be used for?

• calcium hydroxide, Ca(OH)2, is added to fields to increase the soil Ph

• used as anti acids for treating acid digestion

22

What do halogens exist as?

Diatomic molecules

23

Trends down group 7(the halogens)

More electrons

Stronger London forces

Boiling point increases

24

What is the most common type of reaction of the halogens?

Redox reactions

25

Are halogens oxidising agents?

Yes, they oxidise another species

26

How does reactivity change down group 7?

Reactivity of halogens decreases down the group

27

For displacement of halogens, a solution of each halogen is added to aqueous solutions of the other halides. What happens if the halogen added is more reactive than the halide present?

• a reaction takes place, the halogen displaces the halide from solution

• the solution changes colour

28

Colour of Cl2+Br-

Orange from Br2 formation

29

Colour of Cl2+ I-

Violet from I2 formation

30

Colour of Br2 + I-

Violet from I2 formation

31

Colour of Cl2

Pale green

32

Colour and state of fluorine

Pale yellow gas

33

What is a disproportionation reaction?

A redox reaction in which the same element is both oxidised and reduced

34

How do you test for carbonates?

Add dilute nitric acid

If you see bubbles it could be a carbonate

Bubble the gas through lime water (calcium hydroxide, Ca(OH)2

CO2 reacts to form a white precipitate if calcium carbonate which turns the limewater cloudy

35

How to test for sulfates

Add Ba2+ ions as barium chloride or barium nitrate

(Use barium nitrate if you plan to carry out a halide test afterwards)

A white precipitate of barium sulfate, BaSO4, is formed

36

How to test for halides

Add aqueous silver nitrate, AgNO3

White precipitate : silver chloride
Cream precipitate : silver bromide
Yellow : silver iodide

Add aqueous ammonia to test the solubility

Cl- : soluble in solute NH3
Br- : soluble in conc NH3
I- : insoluble in conc NH3

37

Are bromide ions soluble in dilute NH3?

No, they are soluble in concentrated NH3

38

Are iodide ions soluble in dilute NH3?

No, they are not soluble in conc NH3 either

39

What order should the tests for anions be carried out?

Carbonate test

Sulfate test

Halide test

40

How do you test for ammonium ion, NH4?

Add aqueous sodium hydroxide, NaOH

Ammonia gas is produced

The mixture is warmed and ammonia gas is released

Indicator paper will turn blue

41

What is enthalpy?

A measure of the heat energy is a chemical system

Often thought of as the energy stored within bonds

Cannot be measured however enthalpy changes can

42

How do you calculate the enthalpy change?

/\H = H(products) - H(reactants)

43

What is an exothermic reaction?

Energy transfer from the system to the surroundings

/\H is negative

The chemical system loses energy

Bonds breaking

44

What is an endothermic reaction?

Energy transfer from the surroundings to the system

/\H is positive

Chemical system gains energy

Bond making

45

What type of reaction has a negative /\H?

An exothermic reaction

46

Does an endothermic reaction have a negative /\H?

No, /\ H is positive for endothermic reactions

47

What is activation energy?

The minimum energy required for a reaction to take place

48

What is the standard enthalpy change of reaction?

The enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation under standard conditions, with all products and reactants in their standard states

49

What is the standard enthalpy change of formation?

The enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions, with all products and reactants in their standard states

50

What is the enthalpy change of formation for an element?

0kJ mol-1

51

What is the standard enthalpy change of combustion?

The enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions, with all products and reactants in their standard states

52

What are the products when a substance reacts completely with oxygen?

The oxides of the elements in the substance

53

What is the standard enthalpy change of neutralisation?

The enthalpy change that accompanies the reaction of an acid by a base to form one mole of H2O under standard conditions, with all products and reactants in their standard states

54

How do you calculate an energy change?

q=mc/\T

55

What is the specific heat capacity of a substance?

The energy required to raise the temperature of 1g of a substance by 1K

56

Why is enthalpy change of combustion calculated to be more than the actual value?

Heat loss to surroundings

Incomplete combustion

Evaporation

Non-standard conditions

57

What is the average bond enthalpy?

The energy required to break one mole of a specified type of bond in a gaseous molecule

58

In what type of reaction are bonds broken?

Endothermic

59

What happens to the bonds in an exothermic reaction?

The bonds are formed

60

How do you calculate average bond enthalpies?

Sum of bond enthalpies in REACTANTS - sum of bond enthalpies in PRODUCTS

61

What is Hess’ law?

If a reaction can take place by two routes, and the starting and finishing conditions are the same, the total enthalpy change is the same for each route

62

Calculating enthalpy changes of formation

Sum of enthalpy changes of PRODUCTS - sum of enthalpy changes of REACTANTS

63

Calculating enthalpy changes of combustion

Sum of REACTANTS - sum of PRODUCTS

64

How do you calculate rate?

Change in concentration / time

65

What factors can affect the rate of a chemical reaction?

Concentration

Temperature

Use of a catalyst

Surface area

66

What is the collision theory?

Two reacting particles must collide for a reaction to occur

67

Under what conditions will a collision be effective?

The particles collide with the correct orientation

The particles have sufficient energy to overcome the activation energy

68

What does a catalyst do?

Changes the rate of a chemical reaction with out undergoing any permanent change itself

Produces an alternative pathway to lower the activation energy

69

What is a homogeneous catalyst?

Has the same physical state as the reactants

70

What happens in an equilibrium system?

The rate of the forward reaction is equal to the rate of the reverse reaction

The concentration of reactants and products do not change

71

What is Le Chatelier’s principle?

When a system in equilibrium is subjected to an external change the system adjusts itself to minimise the effect of that change

72

What happens to an equilibrium when there are more products formed?

The position shifts to the right

73

What happens when the concentration of the reactants in equilibrium increases?

Equilibrium shifts right

74

What happens when the concentration of the products are increased in equilibrium?

The equilibrium position shifts left

75

Where does the equilibrium shift when the temperature is increased?

Shifts in the endothermic direction (/\H is positive)

76

What has happened to the temperature when the equilibrium shifts towards the exothermic direction?(/\H is negative)

Temperature has decreased

77

What must be true for a change in pressure to affect the direction of equilibrium?

All products and reactants must be gases

78

What will happen to the equilibrium position when pressure is increased?

The equilibrium will shift towards the side with fewer molecules

79

How would pressure change if the equilibrium has been shifted to the side with the most molecules?

Pressure will have decreased

80

How does a catalyst effect the position of equilibrium?

It has no change, it only speeds up the rates of both sides equally

81

How do you calculate the equilibrium constant? Kc

Kc = [products] / [reactants]

82

What does a larger value of Kc mean for the position of equilibrium and the concentrations?

The position of equilibrium is further to the right

Concentrations of products are greater compared to the reactants

83

What type of catalyst has a different chemical state from from the reactants?

Heterogeneous catalyst

84

In what state are heterogeneous catalyst usually used in?

Solids in contact with gaseous reactants or reactants in solution

Reactant molecules are absorbed into the surface of the catalyst and leave the surface after the reaction by desorption

85

What Kc values indicate a position of equilibrium towards the products?

Kc > 1

86

A Kc value <1 indicates a position of equilibrium that is towards the ...

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