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Chemical changes Flashcards

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1
Q

What happens when metal reacts with oxygen.

A

It produces a metal oxide.

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2
Q

What sort of reaction is the formation of a metal oxide?

A

An oxidation reaction.

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3
Q

Why is the reaction of metal oxide an oxidation reaction?

A

The metals gain oxygen.

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4
Q

Reduction is…

A

Loss of oxygen and gain of electrons

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5
Q

Oxidisation is…

A

Gain of oxygen and loss of oxygen.

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6
Q

What is the reactivity of a metal related to?

A

Its tendency to form positive ions

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7
Q

The higher up the reactivity series an element is…

A

… the more easily they form positive ions.

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8
Q

How is the reactivity series related to water and acids?

A

When metals react with water or acid, they lose electrons and form positive ions. So, the higher a metal is in the reactivity series, the more easily it reacts with water or acid.

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9
Q

What 2 elements are included in the reactivity series that aren’t metals?

A

Carbon and Hydrogen

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10
Q

What is the reactivity series

A

Potassium
Sodium
Llithium
Calcium
Magnesium
Carbon
Zinc
Iron
Copper

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11
Q

What do metals react with acid to produce?

A

Salt and Hydrogen.

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12
Q

What do metals react with water to produce?

A

Metal hydroxide and hydrogen

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13
Q

How are metals found on Earth?

A

Unreactive metals such as gold are found in the Earth as the metal
itself but most metals are found as compounds that require
chemical reactions to extract the metal.

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14
Q

How can metals less reactive than oxygen react?

A

Metals less reactive than carbon can be extracted from their oxides
by reduction with carbon.

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15
Q

Oxidation and Reduction in terms of electrons.

A

Oxidation is the loss of electrons and reduction is the gain of
electrons.

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16
Q

What are acids neutralised by to form?

A

Acids are neutralised by alkalis (eg soluble metal hydroxides) and
bases (eg insoluble metal hydroxides and metal oxides) to produce salts and water and by metal carbonates to produce salts, water and carbon dioxide.

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17
Q

What do acids produce in aqeuous solution?

A

Hydorgen ions (+)

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18
Q

What do aqueous solutions of alkalis contain?

A

Hydroxide ions (OH^-)

19
Q

How can the pH of a substance be measured?

A

Universal indicator or pH probe.

20
Q

How does an indicator work?

A

An indicator is a dye that changes colour depending on whether it’s above or below a certain pH. A universal indicator contains a mixture of dyes that means it gradually changes colour over a broad range of pH.

21
Q

What happens in neutralisation reactions between an acid and an alkali?

A

The hydrogen ions react with the hydroxide ions.

21
Q

What is the equation for hydrogen ions reacting with hydroxide ions?

A

H^+ (aq) + OH^-(aq) —> H2O(l)

22
Q

What does titration measure?

A

The volume of acid and alkali solutions that react with each other.

23
Q

What is a strong acid?

A

A strong acid is completely ionised in aqueous solution.

24
Q

What are examples of weak acids?

A

Examples of weak acids are ethanoic, citric and carbonic acids.

24
Q

Examples of a strong acid

A

Sulfuric, nitric, hydrochloric acid

24
Q

What is a weak acid?

A

Weak acids are partially ionised in water.

25
Q

The stronger an acid…

A

The lower the pH.

26
Q

What is pH the measure of?

A

The concentration of hydrogen ions.

27
Q

What is the correlation between pH and hydrogen ion concentration?

A

As the pH decreases by one unit, the hydrogen ion concentration of
the solution increases by a factor of 10.

28
Q

What are electrolytes?

A

Liquids and solutions that are able to conduct electricity as ions are free to move about within it.

29
Q

Describe the process of electrolysis.

A

Passing an electric current through electrolytes causes the ions to move to the electrodes. Positively charged ions move to the negative electrode (the cathode), they gain electrons and are reduced, and negatively charged ions move to the positive electrode (the anode), they lose electrons and are oxidised. Ions are discharged at the electrodes producing uncharged elements.

30
Q

Why cant ionic solids be electrolysed but molten ionic compounds can?

A

The ions are in fixed positions and cannot moves in solids but can move freely and conduct electricity in molten ionic compounds.

31
Q

Describe the electrolysis of molten ionic compounds.

A

When a simple ionic compound (eg lead bromide) is electrolysed in the molten state using inert electrodes, the metal (lead) is produced at the cathode and the non-metal (bromine) is produced at the anode.

31
Q

What can we use electrolysis to do?

A

Extract metals from molten compounds.

32
Q

When is electrolysis used for metal extraction?

A

Electrolysis is used if the metal is too reactive to be extracted by
reduction with carbon or if the metal reacts with carbon.

33
Q

What is the example of metal extraction using electrolysis?

A

Aluminium is manufactured by the electrolysis of a molten mixture
of aluminium oxide and cryolite using carbon as the positive
electrode (anode).

34
Q

Why is a mixture used for the electrolysis of aluminium?

A

Aluminium oxide has a very high melting temperature, so it’s mixed with cryolite to lower the melting point.

35
Q

Why must the positive anode in the extraction of aluminium be regularly replaced?

A

It reacts with oxygen to form carbon dioxide.

36
Q

How is aluminium produced?

A

Metals form, positive ions so the aluminium ions are attracted to the negative electrode and produces aluminum.

37
Q

What is produced at the negative electrode of electrolysis of aqueous solutions?

A

At the negative electrode (cathode), hydrogen is produced if the metal is more reactive than hydrogen. If not, a solid layer of the pure metal will be produced instead.

38
Q

Half equation when hydrogen is produced.

A

2H+ + 2e- → H2

38
Q

What is produced at the positive electrode of electrolysis of aqueous solutions?

A

At the positive electrode (anode), oxygen is produced unless the
solution contains halide ions when the halogen is produced. Those will be chlorine, bromine or iodine molecules.

Chemistry (9 decks)

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