Topic 4: Predicting and Identifying Reactions and Products Flashcards
1
Q
What are Group 1 metals known as?
A
Alkali Metals
2
Q
What happens to Group 1 metals when they react with water?
A
Form alkaline solutions
3
Q
What are the Group 1 metals?
A
- Lithium
- Sodium
- Potassium
- Rubidium
- Caesium
- Francium
4
Q
What similar characteristic do the alkali metals share?
A
- Share similar characteristic chemical properties because they each have one electron in their outermost shell
5
Q
What are some of the properties of an alkali metal?
A
- Soft metals easily cut by knife
- Relatively low densities
- Very reactive (only need to lose one electron to become stable)
6
Q
True or False: The reactivity of the Group 1 metals decrease as you go down the group.
A
- False, it increases as you go down the group as the outermost electron is further away from nucleus so there are weaker forces of attraction and less energy is needed to overcome so the electron is lost more easily
7
Q
How does lithium react with water?
A
Lithium + Water –> Lithium Hydroxide + Hydrogen
- Relatively slow reaction
- Doesn’t melt
- Fizzing can be seen and heard
8
Q
How does sodium react with water?
A
Sodium + Water –> Sodium Hydroxide + Hydrogen
- Large amount of heat released causes Na to melt
- Hydrogen released catches fire causing ball of sodium to dash across surface
9
Q
How does potassium react with water?
A
Potassium + Water –> Potassium Hydroxide + Hydrogen
- Reacts more violently than sodium
- Enough heat released so hydrogen burns with lilac flame and melts into shiny ball that dashes around surface
10
Q
What happens when alkali metals react with oxygen?
A
- Form metal oxides
- Causes alkali metals to tarnish when exposed to air
- Dull coating which covers surface of metal
11
Q
What happens when alkali metals react with chlorine?
A
- React vigorously when heated with chlorine gas to form salts called metal chlorides
- Become more vigorous moving down group
12
Q
What are elements in Group 7 known as?
A
Halogens
13
Q
Name the Group 7 elements
A
- Fluorine
- Chlorine
- Bromine
- Iodine
- Astatine
14
Q
Why do all halogens have similar reactions?
A
Each have seven electrons in their outermost shell
15
Q
Why are halogens diatomic?
A
Form molecules made up of pair of atoms sharing electrons (form a single covalent bond between two halogen atoms)
16
Q
What is the state and characteristics of fluorine?
A
- Yellow Gas
- Very reactive, poisonous gas
17
Q
What is the state and characteristics of chlorine?
A
At room temp. : Pale yellow-green gas
In solution: Pale green
- Reactive, poisonous and dense gas
18
Q
What is the state and characteristics of bromine?
A
At room temp. : Red-brown liquid
In solution: Orange
- Dense red-brown volatile liquid
19
Q
What is the state and characteristics of iodine?
A
At room temp. : Purple-black solid
In solution: Dark brown
- Shimmery, crystalline solid, sublimes to form a purple vapour
20
Q
What happens to the melting and boiling points of halogens throughout the group?
A
- Points increase as you go down the group as there will be increasing intermolecular forces as atoms become larger, so more energy is required to overcome forces
21
Q
What is the differences in physical state and colour when going throughout the halogens?
A
- As you go down, state goes from gas –> solid
- Colour becomes darker as you go down
22
Q
What occurs in a halogen displacement reaction?
A
When a more reactive halogen displaces a less reactive halogen from an aqueous solution of its halide
23
Q
What are the elements in Group 0 known as?
A
Noble gases
24
Q
What are noble gases?
A
Non-metal, monatomic, colourless, non-flammable gases at room temp.
25
Why are noble gases unreactive?
Have a full outer shell of electrons making its electronic configuration extremely stable and do not need to lose or gain electrons
26
What are the uses of Group 0 elements?
Helium - Filling balloons and weather balloons as it is less dense than air and doesn't burn
Neon, Argon and Xenon - Advertising Signs
Argon - Provide inert atmosphere for welding, Fill light bulbs
27
What are the physical properties of the noble gases?
- Low melting and boiling points
- Elements further down have higher boiling points but still lie below 0 ºC
28
Where are the transition metals located in the Periodic Table?
Groups 2 and 3
29
What are the physical properties of transition metals?
- Lustrous, hard, strong and good conductors of heat and electricity
- Highly dense and have high melting points
30
What are transition metals commonly used as?
Transition metals are commonly used as catalysts
31
Do transition metals take part in the reactions they catalyze?
No
32
What allows transition metals to act as good catalysts?
Their ability to interchange between different oxidation states
33
Name a common transition metal catalyst used in the Haber Process.
Iron (Fe) is used as a catalyst in the Haber Process.
34
Which catalyst is used in the Contact Process for sulfuric acid production?
Vanadium pentoxide (V₂O₅) is used in the Contact Process.
35
Which transition metal is used in the hydrogenation of alkenes?
Nickel (Ni) is used in the hydrogenation of alkenes.
36
Why are scandium and zinc not considered transition metals?
They do not form colored compounds and have only one oxidation state.
37
How does reactivity change for Group 1 and 2 metals down the group?
They become more reactive as you go down the group.
38
How does reactivity change for Group 7 (halogens) down the group?
They become less reactive as you go down the group.
39
What type of compounds do Group 1 and 2 metals form with reactive non-metals?
They form ionic compounds.
40
How reactive are Group 0 (noble gases) elements?
They are unreactive.
41
What is a key difference between Group 1 and transition metal ions?
Group 1 metals form +1 ions
42
Compare the hardness of transition metals vs. Group 1 metals.
Transition metals are harder
43
Compare the melting points of transition metals vs. Group 1 metals.
Transition metals have much higher melting points
44
How does the reactivity of transition metals compare to Group 1 metals?
Transition metals are much less reactive than Group 1 metals.
45
Give an example of Group 1 metal reactivity with oxygen.
Group 1 metals tarnish quickly in air
46
How does iron react with oxygen compared to Group 1 metals?
Iron reacts slowly (weeks) with oxygen and water to form rust
47
How does reactivity change for Group 1 and 2 metals down the group?
They become more reactive as you go down the group.
48
How does reactivity change for Group 7 (halogens) down the group?
They become less reactive as you go down the group.
49
What type of compounds do Group 1 and 2 metals form with reactive non-metals?
They form ionic compounds.
50
How reactive are Group 0 (noble gases) elements?
They are unreactive.
51
What is a key difference between Group 1 and transition metal ions?
Group 1 metals form +1 ions
52
Compare the hardness of transition metals vs. Group 1 metals.
Transition metals are harder
53
Compare the melting points of transition metals vs. Group 1 metals.
Transition metals have much higher melting points
54
How does the reactivity of transition metals compare to Group 1 metals?
Transition metals are much less reactive than Group 1 metals.
55
Give an example of Group 1 metal reactivity with oxygen.
Group 1 metals tarnish quickly in air
56
How does iron react with oxygen compared to Group 1 metals?
Iron reacts slowly (weeks) with oxygen and water to form rust
57
What is the correct test for carbon dioxide?
Bubble gas through limewater (calcium hydroxide solution). Positive result: clear solution turns milky/cloudy due to calcium carbonate formation.
58
What common mistake do students make with CO₂ testing?
Mistaking extinguishing a splint as a positive test - nitrogen also does this. Only limewater test is definitive.
59
Describe the hydrogen test procedure.
Hold burning splint at test tube mouth. Positive result: loud 'pop' from H₂ + O₂ → H₂O combustion. Keep splint at mouth for air mixing.
60
Why is oxygen tested with a glowing splint?
Glowing splint relights in oxygen (O₂ supports combustion). Contrast with H₂ test which uses burning splint.
61
What happens in the chlorine test?
Damp blue litmus: 1) Turns red briefly (acidic), 2) Bleaches white (Cl₂ oxidizes dye). MUST use fume cupboard.
62
Why can't you rely on chlorine's smell for testing?
Though distinctive ('swimming pool'), smell is subjective and unsafe. Exam requires litmus bleaching observation.
63
How do you test for metal cations with NaOH?
Add NaOH dropwise: 1) Observe initial precipitate color 2) Add excess - some redissolve (Al³⁺, Zn²⁺), others don't (Mg²⁺, Ca²⁺).
64
What are the colored precipitates from NaOH tests?
Cu²⁺: blue; Fe²⁺: green; Fe³⁺: red-brown; Al³⁺/Mg²⁺/Ca²⁺: white (Al³⁺/Zn²⁺ dissolve in excess NaOH).
65
Describe the carbonate ion test.
Add dilute acid → effervescence (CO₂ gas). Confirm by bubbling gas through limewater → milky precipitate (CaCO₃).
66
Explain the sulfate test procedure.
1) Acidify with HCl (removes CO₃²⁻ interference) 2) Add BaCl₂ → white BaSO₄ precipitate forms if SO₄²⁻ present.
67
Why must HNO₃ be used for halide tests?
HCl would add Cl⁻ ions, causing false AgCl white precipitate. HNO₃ acidifies without contamination.
68
What colors identify silver halides?
AgCl: white; AgBr: cream; AgI: yellow. Colors distinguish Cl⁻, Br⁻, I⁻ in qualitative analysis.
69
List flame test colors for cations.
Li⁺: red; Na⁺: yellow; K⁺: lilac; Ca²⁺: orange-red; Cu²⁺: blue-green. Use clean wire in roaring blue flame.
70
Why clean flame test wire with acid?
Removes previous metal ions to prevent contamination. Nichrome/platinum wires are chemically inert.
71
How does flame photometry improve on flame tests?
Measures exact emission wavelengths, allowing: 1) Multi-ion analysis 2) Concentration quantification via calibration curves.
72
What does a mass spectrum's molecular ion peak show?
Rightmost peak (highest m/z) = molecular mass (M⁺). E.g., peak at 142 → C₁₀H₂₂ (10×12 + 22×1 = 142).
73
How are isotopes identified via mass spec?
Peak heights show relative abundance. E.g., boron-10 (19.9%) vs boron-11 (80.1%).
74
List 4 advantages of instrumental analysis.
1) Higher sensitivity (detects tiny amounts) 2) Faster results 3) Automated multi-sample processing 4) Objective digital data
75
Why is instrumental analysis more accurate than chemical tests?
1) Eliminates human error in color interpretation 2) Precise measurements 3) Computerized pattern matching
76
What's the difference between 'colorless' and 'clear'?
Colorless = no pigment (e.g. water). Clear = transparent (may be colored like blue CuSO₄ solution).
77
Why acidify before SO₄²⁻/halide tests?
Removes CO₃²⁻ interference which also forms precipitates (e.g., BaCO₃ could mimic BaSO₄).
78
How are calibration curves used?
Plot known concentrations vs instrument readings (e.g., light intensity). Compare unknown sample to curve.
79
Describe flame emission spectroscopy.
1) Sample vaporized in flame 2) Emitted light split into spectrum 3) Line patterns identify elements 4) Intensity quantifies concentration.
80
What are common mass spec fragments?
m/z 29 (C₂H₅⁺), 18 (H₂O⁺), 28 (CO⁺), 44 (CO₂⁺). Patterns help identify organic structures.
81
How to distinguish Ca²⁺ from Al³⁺ in NaOH tests?
Both form white precipitates but: Ca(OH)₂ insoluble in excess NaOH, Al(OH)₃ dissolves forming [Al(OH)₄]⁻ complex.
82
What safety precautions are needed for Cl₂ testing?
Use fume cupboard - chlorine is toxic. Avoid inhalation and skin contact with gas.
83
Why use roaring blue flame for flame tests?
Hotter flame excites electrons more, giving brighter colors. Yellow safety flame masks test colors.
84
How does Ag⁺ identify halides?
Ag⁺ + X⁻ → AgX precipitate: Cl⁻=white, Br⁻=cream, I⁻=yellow. Acidification prevents CO₃²⁻ interference.
85
What does limewater test confirm?
CO₂ presence via Ca(OH)₂ + CO₂ → CaCO₃ (milky) + H₂O. Distinguish from other non-acidic gases.
86
How to handle mixed cation samples?
Use instrumental methods (flame photometry/mass spec) as chemical tests require separation first.
87
What type of reaction is the thermite reaction and what metals are involved?
It is a displacement and redox reaction involving aluminium (more reactive) and iron(III) oxide (less reactive).
88
Why is the thermite reaction considered exothermic?
Because it releases a large amount of heat, enough to produce molten iron.
