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GCSE Chemistry > 3) Chemical Changes > Flashcards

3) Chemical Changes Flashcards

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1
Q

What do acids and alkalis combine to form?

A

Water

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2
Q

What substance do acids form when they disolve in water?

A

Hydrogen (H+) ions

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3
Q

What substance do alkalis form when they disolve in water?

A

Hydroxide (OH-) ions

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4
Q

What is an alkaki a type of?

A

Base

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5
Q

How is the strength of an acid determined?

A

By how much it dissolves in water

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6
Q

What are examples of strong acids?

A

Hydrochloric acid
Sulfuric acid
Nitric acid

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7
Q

What do strong acids do in water?

A

Fully ionise (all acid molecules form H+ ions)

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8
Q

What are examples of weak acids?

A

Ethanoic acid

Most acids

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9
Q

At pH 0 what is the concentration of H+ ions?

A

1 mol/dm^3

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10
Q

At pH 1 what is the concentration of H+ ions?

A

1 x 10^-1 mol/dm^3

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11
Q

How can you measure pH?

A

Universal indicator

pH probe

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12
Q

What does a pH probe return?

A

A number

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13
Q

What indicators can be used to determine if a substance is acid or alkali?

A

Methyl orange
Litmus paper
Phenolphthalien

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14
Q

What colour is methyl orange for pH?

A

Red in acid

Yellow in alkali

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15
Q

What colour is litmus paper for pH?

A

Red in acid

Blue in alkali

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16
Q

What colour is phenolphtalein for pH?

A

Colourless in acid

Pink in alkali

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17
Q

How can we measure the change in pH?

A

By adding a solid base to a fixed volumee of acid and measuring the pH

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18
Q

What are the steps of measuring change in pH?

A

1) Use measuring cylinder to add set volume of acid
2) Estimate and record pH of beaker contents
3) Measure out mass of base onto paper or weighing boat
4) Add powered base to beaker
5) Stir and estimate and record mixture pH
6) Repeat step 4 until max pH of 14

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19
Q

What is a concentrated solution?

A

A solution containing a large amount of solute in the same volume of solvent

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20
Q

What is a dilute solution?

A

A solution containing a small amount of solute in the same volume of solvent

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21
Q

What forms when acids react with metals?

A 
Hydrogen 
A salt (first name from involved metal)
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22
Q

What does zinc + sulfuric acid make?

A

–> zinc sulfate + hydrogen

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23
Q

What does sulfuric acid form?

A

Sulfates

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24
Q

What does hydrochloric acid form?

A

Chlorides

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25
Q

What does nitric acid form?

A

Nitrates

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26
Q

How can acid be neutralised?

A

By reacting it with a base

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27
Q

What are examples of bases?

A

Metal carbonates
Metal oxides
Metal hydroxides

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28
Q

What forms when acids react with metal oxides?

A

Acid + oxide –> salt + water

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29
Q

What forms when acids react with metal hydroxides?

A

Acid + hydroxide –> salt + water

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30
Q

What forms when acids react with metal carbonates?

A

Acid + carbonate –> salt + water + carbon dioxide

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31
Q

What is the symbol for sulfate?

A

SO4^2-

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32
Q

What is the symbol for calcium?

A

Ca^2+

33
Q

What is the symbol for sodium?

A

Na+

34
Q

What is the symbol for chloride?

A

Cl-

35
Q

What is the symbol for carbonate?

A

CO3^2-

36
Q

What is the symbol for bromide?

A

Br-

37
Q

What is the test for hydrogen?

A

Place lit splint close to mouth of test tube containing a gas

38
Q

What is the test for carbon dioxide?

A

Take aqueous solution of limewater and bubble through the gas
Limewater turns from clear to cloudy

39
Q

What are soluble salts?

A

Salts that dissolve in water

40
Q

How are blue copper sulfate crystals produced?

A

Adding black copper oxide to sulfuric acid

41
Q

What are the process of the core practical for separating mixtures?

A

1) Warm acid with Bunsen burner
2) Add insoluble solid (with stirring) until reaction no longer happens
3) Filter solution to remove excess insoluble solid
4) Heat solution in evaporating basin above a beaker of water
5) Let solution coola nd allow water to evaporate
6) Concentration becomes more concentrated and salt begins to crystallise

42
Q

What is crystallisation?

A

Evaporating the water of a solution to concentrate and solidify the salt

43
Q

What so soluble salts do as their giant ionic lattice breaks?

A

Dissociate into their anion and cation

44
Q

What salts are usually soluble in water?

A

All nitrates
Chlorides
Sulfates

45
Q

What salts are usually insoluble in water?

A

Carbonates

Hydroxides

46
Q

What is an insoluble solid produced in a reaction called?

A

A precipitate

47
Q

Are precipitates soluble or insoluble?

A

Insoluble

48
Q

What is the product of neutralisation reactions?

A

Water

49
Q

What does titration measure?

A

The volumes of acid and alkali solutions needed in a neutralisation reaction

50
Q

What are suitable indicators for strong and weak acids?

A

Methyl orange

Phenolphthalein

51
Q

What is the process of the titration practical?

A

1) Add set volume of strong acid to conical flask with pipette
2) Add drops of suitable indicator
3) Place strong acid of known concentration into burette
4) Take initial reading of volume of acid in burtte
5) Gradually add acid to alkali, regularly swirling conical flask and adding acid at slower rate
6) Stop adding acid when indicator changes colour
7) Take final reading of volume of acid in burette
8) Subtract final reading from initial reading to calculate volume of acid needed to neutralsie alkali

52
Q

What is the equivalence point on titration curves?

A

In the middle of the large pH change

53
Q

What does electrolysis do?

A

Splits ionic compounds into the different elements that they are amde of

54
Q

What are electrolytes?

A

A solution that conducts electricity due to dissolved ionic compounds

55
Q

What happens when ionic compounds melt or dissolve in water?

A

Ions are free to move and the liquid/solution will conduct electricity

56
Q

What happens when a voltageis applied across an electrolyte?

A

The charged ions are attracted to the electrode of the opposite charge

57
Q

What electrode are cations attracted to?

A

Negative cathode

58
Q

What electrode are anions attracted to?

A

Positive cathode

59
Q

What happens when an ion touches an electrode?

A

Electrons can be transferred which produces elements

60
Q

What is electrolysis used for with ores?

A

To extract reactive metals

61
Q

What happens at carbon anodes?

A

Oxygen forms and reacts to give carbon dioxide

62
Q

Why are anodes usually made of carbon?

A

It is a good electrical conductor and is cheap

63
Q

What happens at the cathode when extracting metals from ores?

A

Aluminium forms

64
Q

What are disadvantages of electrolysis?

A

Lots of energy is needed which costs a lot of money

65
Q

What are the products of electrolysis of molten lead bromide?

A

Lead at cathode (shiny metal)

Bromine at the anode (brown gas)

66
Q

What are the products of electrolysis of copper chloride solution?

A

Copper at cathode

Chlorine at anode (smell + bleaches litmus paper)

67
Q

What are the products of electrolysis of concentrated aqueous sodium chloride?

A

Hydrogen gas at cathode (squeaky pop)

Chlorine at anode (smell + bleaches litmus paper)

68
Q

What are the products of electrolysis of dilute sulfuric acid?

A

Hydrogen gas at cathode (squeaky pop)

Oxgen at anode (relit glowing splint)

69
Q

What are the products of electrolysis of sodium sulfate?

A

Hydrogen at cathode (squeaky pop)

Oxygen at anode (relit glowing splint)

70
Q

Why are electrolysis products of aqueous solutions difficult to predict?

A

Water molecules split up to give H+ and OH- ions

71
Q

What is formed at the cathode of aqueous solutions?

A

Hydrogen if the metal is above hydrogen in the reactivity series
Metal if the metal is lower than hydrogen in the reactivity series

72
Q

What is formed at the anode of aqueous solutions?

A

If halide ions are present the respective halogen forms

If there are no halide ions, oxygen forms

73
Q

What do half equations show in electrolysis?

A

The reactions taking place at each electrode

74
Q

What reaction happens at the anode?

A

Oxidation reactions –> negatively charged ions lose electrons

75
Q

What reaction happens at the cathode?

A

Reduction reactions –> positively charged ions gain electrons

76
Q

What are the results of electrolysis of copper sulfate?

A

Impurities at anode fall to bottom of beaker

When mass of cathode is constant, purification process is complete

77
Q

What type of resistor keeps current constant?

A

Variable resistor

78
Q

How do you measue the mass of copper forming on the cathode over time?

A

1) Record initial mass of electrodes
2) Cathode must be cleaned for the copper to stick to it
3) Wash electrodes to remove copper sulfate
4) Wash electrodes with more volatile solvent to make them dry faster

GCSE Chemistry (10 decks)

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