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C3 Flashcards

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1
Q

What is the formulae for the ion ammonium?

A

NH4^+

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2
Q

What is the formulae for the ion hydrogen?

A

H^+

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3
Q

What is the formulae for the ion lithium?

A

Li^+

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4
Q

What is the formulae for the ion sodium.

A

Na^+

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5
Q

What is the formulae for the ion potassium?

A

K^+

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6
Q

What is the formulae for the ion silver?

A

Ag^+

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7
Q

What is the formulae for the ion Barium?

A

Ba^2+

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8
Q

What is the formulae for the ion calcium?

A

Ca^2+

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9
Q

What is the formulae for the ion copper(II)

A

Cu^2+

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10
Q

What is the formulae for the ion Iron(II)?

A

Fe^2+

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11
Q

What is the formulae for the ion lead(II)?

A

Pb^2+

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12
Q

What is the formulae for the ion magnesium?

A

Mg^2+

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13
Q

What is the formulae for the ion aluminium?

A

Al^3+

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14
Q

What is the formulae for the ion Iron(III)?

A

Fe^3+

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15
Q

What is the formulae for the ion chloride?

A

Cl^-

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16
Q

What is the formulae for the ion Bromide?

A

Br^-

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17
Q

What is the formulae for the ion Iodide?

A

I^-

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18
Q

What is the formulae for the ion hydroxide?

A

OH^-

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19
Q

What is the formulae for the ion nitrate?

A

NO3^-

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20
Q

What is the formulae for the ion oxide?

A

O^2-

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21
Q

What is the formulae for the ion carbonate?

A

CO3^2-

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22
Q

What is the formulae for the ion sulfate?

A

SO4^2-

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23
Q

How do you write the formulae for ionic compounds?

A

In any ionic compound the total number of positive charges must equal the total number of negative charges.

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24
Q

How do I balance compound ions?

A

Magnesium hydroxide

Mg^2+ =magnesium

OH^- =hydroxide

You need 2 hydroxides to get two negative charges to balance magnesium’s positive charge.

Mg(OH)2

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25
Q

What is the law of conservation of mass?

A

Atoms cannot be created or destroyed by chemical reactions. The same atoms are present at the start and end of a reaction. They are just joined in a different way, so the total mass stays the same during the chemical reaction.

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26
Q

How can you investigate conservation if mass?

A

You can investigate conservation if mass by carrying out a reaction in a closed system.This is a container in which no substances can enter or escape during the reaction.
Examples:
-A beaker of reactants in solution where the products are not gases
-A flask attached to a gas syringe to stop products in the gas state escaping

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27
Q

Example of conversation of mass:

A

C + OO —> OCO

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28
Q

Why does the mass seem to change during some reactions?

A

Substances can leave or enter the reaction mixture in a non-enclosed system. This usually happens when a gas is involved as the gas can leave the reaction or join if it is per day airborne.

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29
Q

What is (s) ?

A

Solid

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30
Q

What is (l) ?

A

Liquid

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31
Q

What is (g) ?

A

Gas

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32
Q

What is (aq) ?

A

Aqueous solution

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33
Q

What are half equations?

A

A half equation is a model for the change that happens to one reactant in a chemical equation.
Example:

2Na (s) + Cl2 (g) —> 2Nacl (s)

Sodium ions form when sodium atoms lose electrons. This equation models the change:

Na —> Na^+ + e^-

Chloride ions form when chlorine atoms gain electrons. However chlorine atoms are joined together by covalent bonds to make diatomic chlorine molecules, so this is the half equation the models the change:

Cl2 + 2e^- —> 2Cl^-

Notice you must balance the charges in half equations, not just the number of atoms and the ions they form.

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34
Q

What are ionic equations?

A

A complete ionic equation shows the ions present in a reaction mixture l. It usually also includes the formulae of any molecular substances present, or substances in their solid state.

Example:

HCl (aq) + NaOH (aq) —> NaCl (aq) + H2O (l)

The ionic equation:
H^+(aq) + Cl^- (aq) + Na^+ (aq) + OH^- (aq) —> Na^+ (aq) + Cl^- (aq) + H2O (l)

H2O is modelled as H2O as water is a molecular substance (l)

Any ions that appear on both sides are spectator II s because they are in the reaction but don’t take part in the reaction. A net ionic equation leaves out the spectator ions.

H^+ (aq) + OH^- (aq) —> H2O (l)

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35
Q

What is a mole?

A

The mole is the unit for an amount of substance. One mole of something contains the same number of sheets as the number of carbon atoms. This number is huge. If you could stack a mole of sheets of paper on top of each other, they would reach a quarter size of the way to the centre of our galaxy. It makes little sense to use the mole in everyday life, but it is useful for tiny particles like atoms, molecules l, ions, or electrons.

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36
Q

How is the mole defined?

A

1 mole is defined as the amount of any substance that contains the same number of entities as there are atoms in 12.0 g of carbon-12 (Mass number 12)

Mole is abbreviated to mol in calculations. Eg 1 mol of water contains 1 mol of water molecules. It would also contain 3 mols of atoms because each H2O molecule contains 3 atoms ( 2 hydrogen atoms, 1 oxygen atom.

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37
Q

How do you calculate masses of reactants and products?

A

A
The mass of a substance is related to its molar mass and amount by this expression:

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

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38
Q

What is a limiting reactant?

A

One reactant is usually in excess in a reaction mixture. More of it is present than is needed to react with the other reactant, so some is left at the end. The other reactant is in a limiting amount. The amount of product formed determined by the amount of the limiting reactant, not by the one in excess.

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39
Q

What is the stoichiometry of an equation?

A

The stoichiometry describes the relative amounts of each substance involved, and is to do with these balancing numbers.

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40
Q

“an oxide of copper”

A

Cu2O

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41
Q

how do you calculate the amount of a substance:

A

mass/molar mass = amount of substance

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42
Q

What is an exothermic reaction?

A

When the temperature of the mixture increases during a chemical reaction.
e.g:
-combustion,fuel burning to cook food
-neutralisation, for example sodium hydroxide solution reacting with dilute hydrochloric acid

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43
Q

What is an endothermic reaction?

A

When temperature of a reaction mixture decreases during a chemical reaction.
e.g:
The reaction between citric acid and sodium hydrogen carbonate in sherbet sweets, which is why they feel cold on your tongue.
photosynthesis in plants, which involves carbon dioxide and water reacting to form sugars by using energy in light.

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44
Q

investigating temperature changes:

A

to find if a reaction involving a solution is exothermic or endothermic:
1-Measure the start temperature of a solution in an insulated container
2-Add the other reactant (reacting substance) and stir.
3-Measure the end temperature of the mixture.
4-Calculate the difference between the start temperature and end temperature
(wear eye protection and make sure if reacting substances are both liquid they both start at the same temperature)

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45
Q

What happens to create reaction profiles?

A

In a chemical reaction, bonds break in the reactants to produce separate atoms, and then new bonds form between the atoms to make the products. The surroundings and everything except the reacting particles themselves. During a chemical reaction ,energy (usually measured in kilojoules) is transferred:

-from the surroundings to break the bonds in the reactants to form separate atoms
-to the surroundings from the reacting particles when bonds form between atoms

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46
Q

What is a reaction profile?

A

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

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47
Q

What is activation energy?

A

Energy must be transferred to the reactant particles to start most chemical reactions. Activation is the minimum energy required for a reaction to start. It is often provided by a flame or by heating, and it breaks bonds in the reactants.

48
Q

What happens in an endothermic reaction profile?

A

In endothermic reactions. More chemical energy is stored in the products than in the reactants.

49
Q

What happens in an exoothermic reaction profile?

A

In an exothermic reaction, less energy is transferred to break bonds than is transferred when new bonds form, so the energy change is negative and energy is transferred to the surroundings.

50
Q

What are redox reactions in terms of oxygen?

A

A redox reaction is a reaction in which reduction and oxidation occur at the same time.

In terms of oxygen:

Reduction = loss of oxygen from a substance
Oxidation = gain of oxygen by a substance

51
Q

Simple explanation of redox reactions with oxygen:

A

A substance will contain oxygen but will then give it to a different substance I.e that substance is the oxidising agent for giving the substance and the other substance is the reduction agent because it causes the other to lose oxygen.

52
Q

What are redox reactions in terms of electrons?

A

It’s basically the reverse of oxygen
Reduction = gain of electrons
Oxidation = loss of electrons

53
Q

What are acids?

A

An acid is a substance that releases hydrogen ions,h^+ (aq) when it dissolves in water to make an aqueous solution.
E.g HCl (aq) —> h^+ (aq) +cl^-

Hydrogen chloride gas (HCl) became hydrochloride acid when dissolved in water the solution contains hydrogen ions and chloride ions.

54
Q

What is a base?

A

A base is a substance, usually a metal oxide or metal hydroxide that can neutralise acids. If a base can dissolve in water, it is also an alkali.

55
Q

What is an alkali?

A

An alkali releases hydroxide ions, OH^- (aq), when it dissolves in water.

56
Q

What is the pH scale?

A

pH < 7 means acidic
pH = 7 means neutral
pH > 7 means alkaline

(0-14), 0 being most acidic, 14 most alkali)

57
Q

What is neutralisation?

A

Neutralisation is the reaction between an acid and a base, or an alkali to form a salt and water only.
The salt depends on the acid and base used.

Acid +base —> salt + water

Acid + alkali —> salt + water

58
Q

What happens when neutralisation occurs?

A

The pH changes when neutralisation happens. It increases if a base or an alkali is added to an acid. If enough base or alkali is added to the acid, the pH many increase from less than 7 to more than 7. The opposite happens if an acid is added to a base or alkali. These changes can be gradual or sudden, depending on the reactants.

59
Q

How do you predict the salt made in neutralisation?

A

If you know the base or alkali used, and the acid used, you can predict the salt made.
1-The names of salts have two parts:
The first part comes from the base or alkali, the exception being the use of ammonia or ammonium carbonate when the name starts with ammonium.

2- the second part of the name comes from the acid used

60
Q

What happens during neutralisation in a solution?

A

H^+ (aq) + OH^- (aq) —> H2O (l)

The hydrogen and hydroxide react to make water.

61
Q

Acid to salt - hydrochloride acid, HCL(aq)

A

Chloride

62
Q

Acid to salt - nitric acid, HNO3(aq)

A

Nitrate

63
Q

Acid to salt - sulfuric acid, H2SO4(aq)

A

Sulfate

64
Q

Acid to salt - phosphoric acid, H3PO4(aq)

A

Phosphate

65
Q

What are carbonates?

A

Carbonates are ionic compounds that contain the carbonate ion, CO3^2-

66
Q

How do carbonates react?

A

Carbonates react with acids to form a salt, plus water and carbon dioxide
In general:

Acid + carbonate —> salt + water + carbon dioxide

67
Q

What does the salt made in a carbonate reaction depend on?

A

The salt made depends upon the acid and carbonate used.

CaCO3 (s) + 2HCl (aq) —> CaCl2 (aq) + H2O (l) + CO2 (g)

The carbon dioxide is released as bubbles in the acid during the reaction.
Calcium carbonate is soluble in water but calcium chloride, the salt formed, is soluble in water. This why a lump of calcium carbonate appears to dissolve if you add acid to it.

68
Q

What happens when acids react with metals?

A

If a metal reacts with a dilute acid, the reaction produces a salt and hydrogen.
In general:
Acid + metal —> salt + hydrogen

69
Q

What does the salt depend on when acids react with metals?

A

The salt depends on the acid and metal used. For example, this equation models the reaction between magnesium and dilute hydrochloric acid.

Mg (s) + 2HCl (aq) —> MgCl2 (aq) +
H2 (g)

The hydrogen is released as bubbles in the acid. As the reaction goes on, soluble magnesium chloride forms. This is why a piece of magnesium ribbon appears to dissolve if you put it into acid, even though magnesium itself is insoluble.

70
Q

What is the difference between a dilute and a concentrated acid?

A

A solution consists of a solute dissolved in a solvent. For a given volume of solution, the greater the amount of solute it contains, the greater it’s concentration. For acids:

-A dilute acid contains a low ratio of acid to volume of solution

-A concentrate acid contains a high ratio of acid to volume solution.

71
Q

What are weak acids and strong acids?

A

Acids release hydrogen ions, H^+ (aq), in aqueous solution. A covalent bond in the acid molecule breaks, producing a hydrogen ion and a negatively charged ion:

Weak acids are partially ionised (only a small fraction of their molecules release H^+ ions)

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

72
Q

Ethanoic acid is a weak acid. This equation models how it reacts in aqueous solution:

A

CH3COOH(aq) <=>CH3COO^- (aq) + H^+ (aq)
The symbol <=> shows that reaction does not go to completion

73
Q

Nitric acid is a strong acid:

A

HNO3 (aq) —> H^+ (aq) + NO3^- (aq)

74
Q

How is pH linked to hydrogen ion concentration?

A

I’m aqueous solution, as the concentration of H^+ (aq) ions increases by a factor of 10, the pH of a solution decreases by 1)

An acid has a lower pH (it’s solution is more acidic) when it is concentrated than when it is dilute.

A strong acid has a lower pH than a weak acid at the same concentration.

75
Q

What is electrolysis?

A

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

76
Q

What do you need for electrolysis to work?

A

You need 3 components
-an electrolyte
-two electrodes
-an electrical supply such as a power pack or battery.

77
Q

What are the two electrodes?

A

The negative electrode, the cathode
And
The positive electrode, the anode.

78
Q

What happens during electrolysis?

A

Positive ions gain electrons at the cathode and become atoms

Negative ions lose electrons at the anode and become atoms

79
Q

What are positive and negative ions called in electrolysis?

A

Anions = negative ions
Cations = positive ions

80
Q

What is a binary ionic compound?

A

A binary ionic compound is a compound that contains just two elements.

81
Q

How do you predict the products of electrolysis?

A

Molten lead bromide, PbBr2(I), consists of lead ions and bromide ions. You can model what happens at the electrodes using half equations:

Lead is produced at the cathode: Pb^2+ + 2e^- —> Pb

Bromine is produced at the anode:
2Br^- —> Br2 + 2e^-

82
Q

What do you say when ions become atoms or molecules at an electrode?

A

You say that the ions have been discharged.

83
Q

What happens to ions at the electrode?

A

Overall, ions move to an oppositely charged electrode during electrolysis. The concentration of ions close to each electrode goes down as ions gain or lose electrons to become atoms. Other ions in the electrolyte can move to replace them by diffusion and convection. This could not happen in ionic compounds in the solid state, which is why ionic compounds in the solid state cannot conduct electricity.

84
Q

What are inert electrodes?

A

Inert electrodes are not changed during electrolysis l. They’re usually made from unreactive metals such as copper or platinum l, or from graphite. Inert electrodes can be used for the electrolysis of many ionic compounds in their liquid state or in aqueous solution (dissolved in water)

85
Q

What happens during the electrolysis of water?

A

Water is naturally partially ionised. It contains small concentrations of hydrogen and hydroxide ions.

H2O(l) <=> H^+ (aq) + OH^-(aq)

86
Q

What happens to water during electrolysis?

A

During electrolysis hydrogen ions are discharged at the cathode as hydrogen in its gas state, and hydroxide ions are discharge at the anode, forming water and oxygen in its gas state.

4H^+(aq) + 4e^- —> 2H2 (g) (reduction)

4OH^- (aq) —> 2H2O(l) + O2 (g) + 4e-(oxidation)

87
Q

What happens during the electrolysis of solutions?

A

An aqueous solution contains ions from a dissolved ionic compound. Unlike a molten electrolyte, it also contains hydrogen ions and hydroxide ions from water. The reactions of each ion compete at the electrodes and only one ion is discharged at each electrode:

-hydrogen is produced at the cathode, but if ions from a less reactive metal then hydrogen are present, that metal is produced instead.

-Oxygen is produced at the anode, but if ions from an element in group 7 element are present at high enough concentration then the group 7 element is produced.

88
Q

How do you determine whether a metal is less reactive than hydrogen?

A

You look at a reactivity series

89
Q

What is the order of the reactivity series?

A

(most reactive)
Potassium
Sodium
Calcium
Magnesium
Aluminium
Zinc
Iron
Tub
Lead
(Hydrogen)
Copper
Silver
Gold
Platinum
(Least reactive)

90
Q

What cations are present in CuCl2(aq)?

A

Cu^2+, H^+

91
Q

What cations are present in CuSO4(aq)?

A

Cu^2+, H^+

92
Q

What cations are present in KBr(aq)?

A

K^+,H^+

93
Q

What cations are present in NaOH(aq)?

A

Na^+,H^+

94
Q

What cations are present in H2SO4(aq)?

A

H^+

95
Q

What anions are present in CuCl2(aq)?

A

Cl^-,OH^-

96
Q

What anions are present in CuSO4(aq)?

A

SO4^2-, OH^-

97
Q

What anions are present in KBr(aq)?

A

Br^-,OH^-

98
Q

What anions are present in NaOH(aq)?

A

OH^-

99
Q

What anions are present in H2SO4(aq)?

A

SO4^2-,OH^-

100
Q

What is produced at the cathode from CuCl2(aq)?

A

Copper

101
Q

What is produced at the cathode from CuSO4(aq)?

A

Copper

102
Q

What is produced at the cathode from KBr(aq)?

A

Hydrogen

103
Q

What is produced at the cathode from NaOH(aq)?

A

Hydrogen

104
Q

What is produced at the cathode from H2SO4(aq)?

A

Hydrogen

105
Q

What is produced at the anode from CuCl2(aq)?

A

Chlorine

106
Q

What is produced at the anode from CuSO4(aq)?

A

Oxygen

107
Q

What is produced at the Anode from KBr(aq)?

A

Bromine

108
Q

What is produced at the Anode from NaOH(aq)?

A

Oxygen

109
Q

What is produced at the Anode from H2SO4(aq)?

A

Oxygen

110
Q

What is electroplating?

A

Electroplating is a type of electrolysis that uses non-inert electrodes; these electrodes change during electrolysis.

111
Q

What happens during electroplating?

A

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

Eg:
A solid silver piece of jewellery would be expensive, so electroplating is often used to coat copper or nickel jewellery with silver:
-The cathode is the piece of jewellery
-The anode Is the piece of silver
-The electrolyte is silver nitrate solution

Silver nitrate solution is used because it contains silver ions and all nitrate salts are soluble in water, so you know the silver nitrate will dissolve.

112
Q

How does electroplating work?

A

During electroplating, metal ions from the electrolyte are discharged on the surface of the object (the cathode). These ions are replaced by metal ions leaving the surface of the anode. Overall, metal leaves the anode and is deposited on the object. This process continues until the anode is used up.

113
Q

What happens during electroplating with silver?

A

Silver atoms lose electrons at the anode: Ag —> Ag^+(aq) + e^-

Silver ions gain electrons at the cathode: Ag^+(aq) + e^- —> Ag^+ (s)

114
Q

How is copper purified?

A

-The conducting part of electrical cables is made from copper. However, copper obtained straight from copper ores must be purified so it can conduct electricity well enough to be useful.

-Copper is purified in a similar way to electroplating, except that both electrodes are made from copper. The anode is impure copper and the cathode is very pure copper

-Copper(II) sulfate solution is commonly used as the electrolyte.

-During electrolysis, the cathode gains copper atoms and increases in mass, while the anode loses copper atoms and decreases in mass. Impurities from the anode fall off and collect underneath it.

115
Q

On an exothermic and endothermic reaction graph, what would be labelled on the y axis?

A

Energy

116
Q

On an exothermic and endothermic reaction graph, what would be labelled on the x axis?

A

Progress of the reaction (time)

Chemistry (6 decks)

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