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chemistry > C4: Chemical Changes > Flashcards

C4: Chemical Changes Flashcards

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1
Q

What happens in oxidation reactions?

A

a substance gains oxygen

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2
Q

What happens in reduction reactions?

A

a substance loses oxygen

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3
Q

What is produced when metals react with oxygen?

A

metal oxides

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4
Q

What happens in terms of electrons when metals react?

A

their atoms lose electrons to form positive ions

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5
Q

What is the reactivity series?

A

a list in which elements are placed in order of how reactive they are

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6
Q

What is produced when metals react with acids?

A

metal salts and hydrogen

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7
Q

What is a displacement reaction?

A

a reaction in which a more reactive metal displaces a less reactive metal from a solution of its salt

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8
Q

What does the method of extraction of a metal depend on?

A

the reactivity of the metal

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9
Q

How can metals that are less reactive than carbon be extracted from their oxides?

A

by heating with carbon

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10
Q

In terms of electrons, what is oxidation and reduction?

A

oxidation is loss of electrons and reduction is gain of electrons

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11
Q

What happens when substances dissolve in water?

A

they dissociate into their individual ions:
-hydroxide solutions, OH-(aq) make solutions alkaline
-hydrogen ions, H+(aq), make solutions acidic

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12
Q

What is the pH scale?

A

a measure of the acidity or alkalinity of an aqueous solution

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13
Q

What pH value would a solution have if it were neutral?

A

7

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14
Q

What range of pH values would an acidic solution have?

A

<7

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15
Q

What range of pH values would an alkaline solution have?

A

> 7

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16
Q

What is an indicator?

A

dye that changes colour depending on whether they are in acidic or alkaline solutions

17
Q

How does litmus change colour in an acidic solution?

A

blue litmus turns red (and vice versa in alkaline)

18
Q

What is universal indicator?

A

a mixture of dyes that shows a range of colours to indicate how acidic or alkaline a substance is

19
Q

How can acids be neutralised by metal oxides and metal carbonates?

A

acid + metal oxide → salt + water
acid + metal carbonate → salt + water + carbon dioxide

20
Q

How is salt produced in a neutralisation reaction?

A

when the hydrogen in the acid is replaced by a metal ion

21
Q

What salt does hydrochloric acid produce?

A

chloride salts

22
Q

What salt does nitric acid produce?

A

nitrate salts

23
Q

What salt does sulfuric acid produce?

A

sulphate salts

24
Q

What is a strong acid?

A

an acid (e.g. hydrochloric, nitric or sulfuric) that is completely ionised in water

25
Q

What is a weak acid

A

an acid (e.g. ethanoic, citric or carbonic) that is only partially ionised in water

26
Q

What is the pH of a solution a measure of?

A

the concentration of H+ ions

27
Q

What does a pH decrease of 1 indicate?

A

the concentration of hydrogen ions has increased by a factor of ten

28
Q

What is electrolysis?

A

the use of an electrical current to break down compounds containing ions into their constituent elements

29
Q

What is the substance being broken down in electrolysis called?

A

the electrolyte

29
Q

What must the electrodes be able to do and what are they usually made of?

A

conduct electricity, graphite

30
Q

What happens during electrolysis?

A

-negatively charged ions move to the anode
positively charged ions move to the cathode

31
Q

What else can electrolysis be used for?

A

separating ionic compounds into elements

32
Q

What sort of reactions happen at the anode?

A

oxidation

33
Q

What sort of reactions happen at the cathode?

A

reduction

34
Q

What is cryolite?

A

a compound of aluminium that lowers the melting point which therefore lowers the overall energy demand of the electrolysis of aluminium oxide

35
Q

What happens to water in the electrolysis of aqueous solutions?

A

it breaks down into hydroxide ions and hydrogen ions

36
Q

What happens at the cathode during the electrolysis of aqueous solutions?

A

-hydrogen is produced if the metal is more reactive than hydrogen
-the metal is produced if it is less reactive than hydrogen

37
Q

What happens at the anode during the electrolysis of aqueous solutions?

A

-oxygen is produced unless the solution contains halide ions
-of halide ions are present then the halogen is produced

chemistry (5 decks)

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