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OCR GATEWAY GCSE CHEMISTRY > C4 Predicting and identifying reactions and products > Flashcards

C4 Predicting and identifying reactions and products Flashcards

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1
Q

What are alkali metals?

A

They are in group 1 so they have 1 electron in their outer shell and form positive ions with a 1+ charge to achieve a full outer shell.

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2
Q

How do alkali metals react with water?

A

-Produce metal hydroxide solutions which are alkaline.
-Alkali metal + Water -> Metal hydroxide + Hydrogen

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3
Q

How do alkali metals react with acids?

A

Alkali metal + Acid -> Salt + Hydrogen

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4
Q

How do alkali metals react with oxygen?

A

Alkali metal + Oxygen -> Metal oxide

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5
Q

How do alkali metals react with halogens?

A

-React vigorously with halogens to form ionic compounds called halide salts:
-Alkali metal + Halogen -> Salt
-Sodium + Chlorine -> Sodium chloride

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6
Q

What are physical properties of alkali metals?

A

-Soft enough to cut with a knife.
-Shiny when freshly cut.
-Low density compared to other metals.
-Tend to appear as a grey solid.

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7
Q

What are the trends as you go down the group of alkali metals?

A

-Density increases.
-Relative atomic mass increases.
-Atomic radius increases.
-Reactivity increases.
-Melting and boiling points decrease.

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8
Q

Why does density increase as you go down the group of alkali metals?

A

As relative atomic mass increases.

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9
Q

Why does atomic radius increase as you go down the group of alkali metals?

A

A new shell is added in each row (period) due to the atomic number increasing.

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10
Q

Why does reactivity increase as you go down the group of alkali metals?

A

As atomic radius increases, the number of electron shells between the outer electron and the nucleus increases, so it’s easier to lose the outer electron and the element is more reactive.

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11
Q

Why do melting and boiling points decrease as you go down the group of alkali metals?

A

As ionic radius increases, the distance between the bonding electrons and the positive nucleus gets larger, reducing the overall attraction and decreasing melting and boiling points.

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12
Q

How does the alkali metal lithium react with water?

A

Lithium + water -> Lithium hydroxide and hydrogen.
2Li + 2H₂O -> 2LiOH + H₂

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13
Q

How does the alkali metal sodium react with water?

A

Sodium + water -> Sodium hydroxide and hydrogen.
2Na + 2H₂O -> 2NaOH + H₂

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14
Q

How does the alkali metal potassium react with water?

A

Potassium + water -> Potassium hydroxide and hydrogen.
2K + 2H₂O -> 2KOH + H₂

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15
Q

What happens when the alkali metal lithium reacts with water?

A
  1. Floats.
  2. Steadily gives off a gas.
  3. Clear alkaline solution left.
  4. Lithium hydroxide formed.
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16
Q

What happens when the alkali metal sodium reacts with water?

A
  1. Floats and moves about more vigorously than lithium.
  2. Melts to a sphere.
  3. Gives off a gas (sometimes the gas will ignite with a yellow flame if the reaction is hot enough).
  4. Clear alkaline solution left.
  5. Forms sodium hydroxide.
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17
Q

What happens when the alkali metal potassium reacts with water?

A
  1. Floats and moves about more vigorously than sodium.
  2. Melts to a sphere.
  3. Gives off a gas (heat of reaction is high enough to ignite H₂ gas with a lilac flame).
  4. Clear alkaline solution left.
  5. Potassium hydroxide formed.
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18
Q

How are metal reactions with water impacted as you go down the group of alkali metals?

A

-Reactions become more vigorous.
-Reactions become hot enough to burn the H₂ gas.
-Metal melts to a sphere faster and fizzes about more.

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19
Q

How can we see the most reactive substance in the group of alkali metals?

A

Measure the rate at which the hydrogen gas is produced.

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20
Q

What are the halogens?

A

-They are in group 7 so they have 7 electrons in their outer shell and form negative halide ions with a 1- charge to achieve a full outer shell.
-Exist as diatomic molecules.
-Go through displacement reactions.

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21
Q

What are diatomic molecules?

A

They form molecules made of pairs of atoms sharing electrons.

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22
Q

What is a displacement reaction?

A

A reaction that occurs when a more reactive element replaces a less reactive element in a compound.

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23
Q

What is a halogen displacement reaction?

A

When a more reactive halogen displaces a less reactive halogen from an aqueous solution of its halide.

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24
Q

What are the 6 displacement reactions of halogens you need to know?

A

-Sodium chloride and chlorine.
-Sodium bromide and chlorine.
-Sodium iodide and chlorine.
-Sodium chloride and bromine.
-Sodium bromide and bromine.
-Sodium iodide and bromine.

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25
Q

What is the displacement reaction between chlorine and sodium chloride?

A

-No reaction.
-Colourless solution.

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26
Q

What is the displacement reaction between chlorine and sodium bromide?

A

-Bromine formed.
-Colour change: colourless to orange-yellow.
-Ionic equation: Cl₂ + 2Br- -> 2Cl- + Br₂

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27
Q

What is the displacement reaction between chlorine and sodium iodide?

A

-Iodine formed.
-Colour change: colourless to orange-red.
-Ionic equation: Cl₂ + 2I- -> 2Cl- + I₂

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28
Q

What is the displacement reaction between bromine and sodium chloride?

A

-No reaction.
-Colour change: colourless to orange-yellow.

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29
Q

What is the displacement reaction between bromine and sodium bromide?

A

-No reaction.
-Colour change: colourless to orange-yellow.

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30
Q

What is the displacement reaction between bromine and sodium iodide?

A

-Iodine formed.
-Colour change: colourless to orange-red.
-Ionic equation: Br₂ + 2Br- -> 2Br- + I₂

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31
Q

What are properties of halogens?

A

-Can’t conduct electricity.
-Brittle and dull.
-Thermal and electrical conductors.

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32
Q

What are the trends as you go down the group of halogens?

A

-Atomic radius increases.
-Melting and boiling points increase.
-Reactivity decreases.

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33
Q

Why does atomic radius increase as you go down the group of halogens?

A

A new shell is added in each row (period) due to the atomic number increasing.

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34
Q

Why do melting and boiling points increase as you go down the group of halogens?

A

More energy required to separate larger molecules due to more covalent bonds holding them together and therefore more intermolecular forces to overcome.

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35
Q

Why does reactivity decrease as you go down the group of halogens?

A

Distance between outer shell and positive nucleus increases therefore the forces of attraction between them decrease which makes it harder to gain electrons to achieve full outer shell.

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36
Q

What is the solution colour, state at room temperature and vapour colour of fluorine?

A

-Solution colour: yellow.
-State at room temperature: gas.
-Vapour colour: yellow.

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37
Q

What is the solution colour, state at room temperature and vapour colour of chlorine?

A

-Solution colour: green.
-State at room temperature: gas.
-Vapour colour: green.

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38
Q

What is the solution colour, state at room temperature and vapour colour of bromine?

A

-Solution colour: red/brown.
-State at room temperature: liquid.
-Vapour colour: red/brown.

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39
Q

What is the solution colour, state at room temperature and vapour colour of iodine?

A

-Solution colour: grey.
-State at room temperature: solid.
-Vapour colour: purple.

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40
Q

What are the noble gases

A

-They are in group 0 so they already have a full outer shell of electrons.
-Every element has 8 electrons in outer shell except for helium which has 2 electrons.
-They are monoatomic.
-Inert (unreactive).

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41
Q

What are monoatomic molecules?

A

Exist as single atoms.

42
Q

Why are the noble gases inert?

A

Their electronic configuration is very stable due to their full outer shell so they don’t need to gain / lose electrons.

43
Q

Why are the group 0 elements gases at room temperature with low melting and boiling points?

A

They have weak intermolecular forces between atoms due to their monoatomic structure therefore very little energy is required to overcome these forces.

44
Q

What are the trends as you go down the group of noble gases?

A

-Atomic radius increases.
-Relative atomic mass increases.
-Density increases.
-Melting and boiling points increase.

45
Q

Why does atomic radius increase as you go down the group of noble gases?

A

A new shell is added in each row (period) due to the atomic number increasing.

46
Q

Why does density increase as you go down the group of noble gases?

A

Due to increasing atomic radius and relative atomic mass.

47
Q

Why do melting and boiling points increase as you go down the group of noble gases?

A

Increasing atomic radius results in more intermolecular forces between atoms therefore more energy is required to overcome these forces and change the state.

48
Q

What are the uses of the noble gases helium, argon and krypton?

A

-Helium: used to fill balloons as it has a lower density than air.
-Argon: used in light bulbs as it doesn’t react with the filament in the light bulb.
-Krypton: used for lasers as it gives bright light during emission.

49
Q

What are transition metals?

A

-Located between groups 2 and 3 in the centre of the periodic table.
-First row is most commonly used.

50
Q

What are properties of transition metals compared to group 1 metals?

A

-Harder and stronger.
-Higher melting and boiling points except mercury.
-Higher densities.
-Less reactive so don’t react as vigorously with oxygen/water.

51
Q

What are other properties of transition metals?

A

-Coloured compounds.
-Thermal and electrical conductor.
-Strong and hard.
-Used as catalysts.
-Form ions with variable charges (different charges).

52
Q

When will compounds have different properties and colours in aqueous solutions?

A

When they contain transition metals in different oxidation state.

53
Q

Where do the catalytic characteristics of transition metals stem from?

A

Their ability to interchange between a range of oxidation states.

54
Q

What are 3 common transition metals and their uses?

A

-Iron: used in Haber process.
-Vanadium: used in Contact process.
-Nickel: used in hydrogenation of alkenes.

55
Q

What is the equation of rust?

A

Iron + water + oxygen -> Iron oxide (rust)

56
Q

Why should gas tests be done in a fume cupboard?

A

To reduce the risk of inhaling a toxic gas.

57
Q

What is the test for oxygen?

A

The glowing splint test:
1. Collect the gas given off by a reaction in a test tube.
2. Take a glowing splint and blow out the flame.
3. Put the embering splint in the test tube.
4. If the flame re-lights, then oxygen is present.

58
Q

What is the test for hydrogen?

A

The burning splint test:
1. Collect the gas given off by a reaction in a test tube.
2. Take a burning splint and hold it to the mouth of the test tube.
3. If hydrogen is present, it will produce a squeaky popping sound.

59
Q

What is the test for carbon dioxide?

A

The bubble through limewater test:
1. Pass the gas given off by a reaction through a U-tube filled with lime water.
2. If carbon dioxide is present, the limewater will go cloudy.

60
Q

Why does limewater go cloudy?

A
  1. The lime mineral reacts with the CO₂ in water.
  2. This forms calcium carbonate and water.
  3. This is white and doesn’t dissolve in water.
  4. Therefore, the limewater goes cloudy.
61
Q

What is the test for chlorine?

A

The damp blue litmus paper test:
1. Collect the gas given off by a reaction in a test tube.
2. Take a piece of damp blue litmus paper and place it in the test tube.
3. Chlorine is present if the litmus paper is bleached, colour change: blue to white.

62
Q

What are the 2 ways to test for cations?

A

-Sodium hydroxide tests.
-Flame tests.

63
Q

How do sodium hydroxide tests work?

A
  1. Metal ions in solution will often react with sodium hydroxide to form metal hydroxide precipitates.
  2. Chemical behaviours of these precipitates and their colours will identify the presence of a given ion in solution.
64
Q

What is the sodium hydroxide test result for Iron (ii)?

A

Green precipitate colour.

65
Q

What is the sodium hydroxide test result for Iron (iii)?

A

Brown precipitate colour.

66
Q

What is the sodium hydroxide test result for Copper (ii)?

A

Blue precipitate colour.

67
Q

What is the sodium hydroxide test result for Calcium?

A

Cloudy white precipitate colour which is insoluble in excess.

68
Q

What is the sodium hydroxide test result for Zinc?

A

Cloudy white precipitate colour which is soluble in excess.

69
Q

How do flame tests work?

A
  1. Metal ions can be burnt to produce flames of different colours.
  2. Colours are characteristic to the metal ion being burnt.
  3. Allows us to identify which metal ion is present in a compound by burning sample of compound.
70
Q

What is the flame test result for lithium?

A

Crimson-red flame colour.

71
Q

What is the flame test result for sodium?

A

Yellow-orange flame colour.

72
Q

What is the flame test result for potassium?

A

Lilac flame colour.

73
Q

What is the flame test result for calcium?

A

Orange-red flame.

74
Q

What is the flame test result for copper (ii)?

A

Green flame colour.

75
Q

What is the process of performing a flame test?

A
  1. Clean nichrome wire in acid to help solid stick to the wire.
  2. Use a blue flame as it’s almost colourless.
  3. Dip wire into a small sample of solid you’re testing.
  4. Place wire back into flame.
  5. Record colour observed.
76
Q

What is a nichrome wire?

A

An alloy of nickel and chromium.

77
Q

Why should a colourless flame be used in a flame test?

A

Colour interferes with flame test result.

78
Q

What must you do when you place the wire back into a flame during a flame test?

A

Ensure the wire doesn’t get too hot that it glows red as this interferes with the flame colour in the test result.

79
Q

Which cations are tested using sodium hydroxide tests?

A

-Iron (ii).
-Iron (iii).
-Copper (ii).
-Calcium.
-Zinc.

80
Q

Which cations are tested using flame tests?

A

-Lithium.
-Sodium.
-Potassium.
-Calcium.
-Copper (ii).

81
Q

How are anions tested for?

A

Range of test tube reactions as carbonate, halide and sulfate ions are commonly found ions in solution.

82
Q

What is the carbonate ion test?

A
  1. Add some barium chloride solution. If there are carbonate ions present, a white precipitate of barium carbonate will be produced.
  2. Add some dilute hydrochloric acid to the solution and collect the gas given off. If there are carbonate ions present, the carbonate will react with the acid to produce carbon dioxide gas.
  3. Test for carbon dioxide by bubbling through limewater.
  4. If carbon dioxide is present, there should be a colourless solution containing Ba2+ ions and carbonate ions are present.
83
Q

What is the equation for the carbonate ion test?

A

BaCO3 (s) + 2HCl (aq) -> Ba2+ (aq) + CO2 (g) + H2O (l)

84
Q

What is the sulfate ion test?

A
  1. Add some barium chloride solution. If there are sulfate ions present, a white precipitate of barium sulfate will be produced.
  2. Add some dilute hydrochloric acid to the solution to confirm that carbonate ions aren’t present.
  3. If sulfate ions are present, the barium sulfate won’t react with the hydrochloric acid as it’s an insoluble compound.
85
Q

What is the equation for the sulfate ion test?

A

SO₄²- + BaCl2 -> BaSO4 + 2Cl-

86
Q

What is the halide ion test?

A
  1. Add some dilute nitric acid to remove any carbonate / sulfate impurities.
  2. Add some silver nitrate solution as halide ions can be identified through their reactions with aqueous silver nitrate to form precipitates.
  3. The different halide ions (Cl-, Br-, I-) produce different colour precipitates.
87
Q

How do you know if dilute nitric acid has successfully removed carbonate / sulfate impurities from a halide ion test?

A

There is fizzing.

88
Q

What happens if Cl- is present in a halide ion test?

A

-Ag- (aq) + Cl- (aq) -> AgCl (s).
-White precipitate produced.

89
Q

What happens if Br- is present in a halide ion test?

A

-Ag- (aq) + Br- (aq) -> AgBr (s).
-Cream precipitate produced.

90
Q

What happens if I- is present in a halide ion test?

A

-Ag- (aq) + I- (aq) -> AgI (s).
-Yellow precipitate produced.

91
Q

What are instrumental methods of analysis?

A

Allow you to analyse and identify known compounds and elements using machines rather than manual chemical tests.

92
Q

Compare instrumental analysis to chemical analysis:

A

-Easier to use.
-Small samples instead of whole sample as modern instruments are sensitive.
-Faster.
-Greater accuracy.
-Give more information about sample.
-Automated instead of manual so can perform multiple simultaneous sampling and testing.

93
Q

What are examples of instrumental analysis?

A

-Mass spectrometry.
-Flame emission spectroscopy.
-Gas chromatography.

94
Q

What is the advantage of flame emission spectroscopy?

A

Spectroscoper can be used with multiple colours from different ions.

95
Q

What is mass spectrometry?

A

-Works out relative molecular masses to identify unknown compounds.
-Determines the relative atomic mass of an element depending on the abundance and mass of each of its isotopes.

96
Q

How does mass spectrometry work?

A
  1. A sample passes through a mass spectrometer.
  2. A spectrum is produced of mass/charge ratio (x-axis) against abundance (y-axis).
  3. The spectrum gives lots of information about a compound.
97
Q

What information does a mass spectrum give about a compound?

A

-The relative isotopic abundance.
-Atomic mass.
-Molecular mass.
-Structure of a compound.

98
Q

What is the m/z value in a mass spectrum?

A

The mass to charge ratio.

99
Q

What does a mass spectrometry graph show?

A

-Heights of peaks show the proportion of each isotope present.
-Molecular ion peak which is the first thing used to identify a compound (gives information about the molecular mass of a compound).

100
Q

What is the molecular ion peak in mass spectrometry?

A

The most important peak in a mass spectrometry graph with the highest m/z value. It’s the peak furthest to the right.

OCR GATEWAY GCSE CHEMISTRY (6 decks)

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