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Flashcards in C3 Deck (81):
1

How do you write the formulae of metal compounds?

A capital letter followed by lowercase letters e.g. Hg

2

How do write the formulae of Group 8 elements?

The group 8 elements are monoatomic e.g. He

3

How do you write the formulae of Group 7 elements?

The group 7 elements are diatomic e.g. Cl (sub) 2

4

How do you write the formulae of simple covalent compounds?

By using the molecular formula e.g. CO (sub) 2

5

What are the 4 rules to write the formulae of common ions?

1. Hydrogen ions have a 1+ charge
2. Metals in groups 1, 2 and 3 have a 1+, 2+ and 3+ charge
3. Transition metals are usually 2+, with some 3+ charges
4. Non-metals in groups 5, 6 and 7 have a 3-, 2- and 1- charge

6

How do you write the formulae of ionic compounds?

By balancing the total number of positive charges with negative charges e.g. MgO

7

How do you write compound ions?

Compound ions are written in the same way, but in brackets if there are 2 or more. E.g. Mg(OH) 2

8

What is the law of conservation of mass?

The mass of a substance at the start of a reaction is equal to the mass of a substance at the end of a reaction

9

Why does the mass seem to go down in reactions?

As gases can escape in a non-enclosed system

10

Why does the mass seem to go up in reactions?

As a metal can react with oxygen in the air which adds mass

11

What does a word equation show?

The names of the reactants and products involved

12

What does a balanced equation show?

How the atoms are rearranged in a reaction, and the relative amounts of each substance involved

13

How do you balance an equation?

By adding numbers so there are equal numbers of atoms of each element of both sides of the equation

14

What are state symbols?

State symbols show the physical state of each substance in a chemical reaction

15

What are the 4 state symbols?

aq, s, l, g

16

What is a half equation?

A half equation is a model for the change that happens to one reactant in a reaction

17

How do you write the half equation for sodium when it reacts with chlorine?

Na --> Na+ + e-

18

How do you write the half equation for chlorine when it reacts with sodium?

Cl2 + 2e- --> 2Cl-

19

What is an ionic equation?

An ionic equation shows the ions present in a reaction mixture

20

What are spectator ions?

Spectator ions are ions that do not take part in the reaction.

21

What is a net ionic equation?

A net ionic equation leaves out the spectator ions

22

What is a mole?

A mole is a unit for amount of substance

23

How many moles of atoms are there in 1 mol of CH4 molecules?

5 moles

24

What are the number of entities in 1 mol?

Avogadro's constant - 6.02x10^23/mol

25

How can you measure the mole of a substance?

The mass of 1 mol of a substance is its molar mass

26

What is the equation linking the amount of substance, molar mass and mass?

mass (g) = molar mass (g/mol) x amount (mol)

27

What is a reactant in excess?

A reactant where more of it is present than to react with the other reactant, so some of it is left at the end

28

What is a limiting reactant?

A reactant where less of it is present than to react with the other reactant, so it determines the amount of product made

29

What is stoichiometry?

A system which describes the relative amounts of each substance involved in a chemical reaction

30

How do you calculate stoichiometry (2 steps)?

1. Calculate the amount of each measured substance in moles
2. Simplify the ratio of these substances

31

What are exothermic reactions?

An exothermic reaction is where the temperatures of the surroundings increases during the reaction

32

What are endothermic reactions?

An endothermic reaction is where the temperatures of the surroundings decreases during the reaction

33

What is a reaction profile?

A reaction profile is a chart that shows the energy involved in a reaction

34

How is energy transferred in a reaction?

Energy is transferred:
1. From the surroundings to break bonds
2. To the surroundings to form bonds

35

What is activation energy?

Activation energy is the energy needed for a reaction to occur

36

What is energy change?

Energy change is the difference between the energy transferred from the surroundings to break bonds and to the surroundings to form bonds

37

Draw and label a reaction profile for an endothermic reaction

see p.g. 105

38

Draw and label a reaction profile for an exothermic reaction

see p.g. 105

39

What are bond energies?

Bond energy is the energy needed to break down 1 mol of a particular bond. It is measured in kJ/mol.

40

How do you calculate energy changes in reactions?

Energy change = energy transferred to break bonds - energy transferred to make bonds

41

What does a negative energy change show and why?

That the reaction is exothermic, as more energy is transferred to the surroundings

42

What does a positive energy change show and why?

That the reaction is endothermic, as more energy is being transferred from the surroundings.

43

What is a redox reaction?

A redox reaction is a reaction were oxidation and reduction happen at the same time

44

What Is reduction in terms of oxygen and electrons?

Reduction is the loss of oxygen and the gain of electrons from a substance.

45

What Is oxidation in terms of oxygen and electrons?

Oxidation is the gain of oxygen and the loss of electrons by a substance

46

What substance is oxidised in the following reaction:
2Al + Fe2O3 --> Al2O3 + 2Fe

Aluminium, because it gains oxygen and is oxidised

47

What substance is reduced in the following reaction:
2Al + Fe2O3 --> Al2O3 + 2Fe

Iron oxide, because it loses oxygen and is reduced

48

What substance is the reducing agent in the following reaction:
2Al + Fe2O3 --> Al2O3 + 2Fe

Aluminum, because it reduces iron oxide to iron

49

What substance is the oxidising agent in the following reaction:
2Al + Fe2O3 --> Al2O3 + 2Fe

Iron oxide, because it oxidises aluminium to aluminium oxide

50

OIL RIG

Oxygen is loss, Reduction is gain

51

What is an acid?

An acid is a substance that releases hydrogen ions , H+ when it dissolves in water to make an aqueous solution.

52

What is a base, and an alkali?

A base is a substance that neutralise acids, and an alkali releases hydroxide ions, OH-, when it dissolves in water

53

What is the pH scale?

The pH scale describes the relative acidity or alkalinity of a substance.
pH = 7 is neutral
pH < 7 is acidic
pH > 7 is alkaline

54

What can you use to measure the pH of a solution?

You can use universal indicator to measure the pH of a solution. You can also use a pH meter. It works by:
1. Wash the pH probe with water, then put it into a calibration buffer
2. Adjust the reading to match the pH of the buffer solution

55

What is neutralisation?

The reaction between an acid and a base, or alkali to produce a salt and water only.
Acid + base —> salt + water

56

What happens during neutralisation in solution?

The hydrogen ions from acidic solutions and hydroxide ions from alkaline solutions react to form water. The salt produced depends on the other ions present.

57

What happens when an acid reacts with a carbonate?

acid + carbonate —> salt + water + carbon dioxide
Carbon dioxide is released as bubbles in the acid

58

What happens when acids react with metals?

acid + metal —> salt + hydrogen
The hydrogen is released as bubbles in the acid

59

What is a dilute acid?

A dilute acid is an acid that contains a low ratio f acid to volume of solution

60

What is a concentrated acid?

A concentrated acid is one that contains a high ratio of acid to volume of solution

61

What are weak acids?

Weak acids are ones that are partially ionised (only a few of their molecules release H+ ions)

62

What are strong acids?

Strong acids are ones that are fully ionised (all of their molecules release H+ ions)

63

What happens as the concentration of hydrogen ions increases?

As the concentration of hydrogen ions ions increases by a factor of 10, the pH of the solution decreases by 1

64

What does a pH titration curve show?

A pH titration curve shows the effect on pH of changing the hydrogen ions concentration during a neutralisation reaction.

65

What is electrolysis?

Electrolysis is a process in which an electric current is passed through a compound, causing an electrical change

66

What do you need for electrolysis to work?

1. An electrolyte, a compound in its liquid state or in solution, contains mobile ions and conducts electricity
2. Two electrodes, which conduct electricity to the electrolyte
3. An electrical supply

67

What happens during electrolysis?

Positive ions gain electrons and become atoms at the cathode
Negative ions lose electrons and become atoms at the anode

68

What are positive and negative ions called in electrolysis?

Positive ions are called cations, which are attracted to the cathode. Negative ions are called anions, which are attracted to the anode.

69

How do you predict the products of electrolysis?

By using half equations to see what happens at each electrode.

70

What are inert electrodes?

Inert electrodes are ones that aren't changed during electrolysis

71

What happens during the electrolysis in solutions?

A solution contains the ions from the ionic compound, but also hydroxide and hydrogen ions from water. The reactions of each ion compete at the electrodes and only one ion is discharged at each electrode.

72

What happens at the anode during the electrolysis of solutions?

Oxygen is produced, but if a group 7 element is present at a high enough concentration then the element is produced instead (and sulfate, nitrate ions)

73

What happens at the cathode during the electrolysis of solutions?

Hydrogen is produced, but if ions from a less reactive metal than hydrogen is present then the metal is produced instead

74

What type of electrolysis uses inert electrodes?

Electroplating

75

What are the roles of the anode, cathode and electrolyte in electroplating?

The cathode is the object you want to coat
The anode is the piece of metal you want to coat the object with
The electrolyte is a solution with ions of the coating metal

76

How does electroplating work?

Metal ions from the electrolyte are discharged on the surface of the object. These ions are replaced by metal ions leaving the surface of the anode. Overall, metal leaves the anode and is deposited on the object.

77

How do ions and electrons move in electroplating?

Ions move through the electrolyte and electrons move through the wires between the two electrodes

78

What is an acid?

An acid is a substance that releases hydrogen ions when it dissolves in water to make an aqueous solution

79

What is a base and an alkali?

A base is a substance that can neutralise acids. If a base can dissolve in water it is an alkali, which releases hydroxide ions when it dissolves in water.

80

What is the pH scale?

The pH scale shows the relative acidity or alkalinity of a substance. pH < 7 is acidic, pH = 7 is neutral and pH > 7 is alkaline

81

What is universal indicator?

Universal indicator is a piece of equipment that you can use to measure the pH of a solution by looking at its colour