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Chemistry Unit 1 > Halogens > Flashcards

Halogens Flashcards

1
Q

What is fluorine at room temperature

A

Fluorine is a pale yellow gas.

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2
Q

What is the physical state of Chlorine at room temperature?

A

Chlorine is a yellow-green gas.

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3
Q

What is bromine at room temperature

A

Bromine is a red-brown liquid at this temperature.

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4
Q

What is iodine at room temperature

A

Iodine is a grey-black solid at room temperature.

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5
Q

What type of molecules do halogens exist as?

A

Covalently bonded diatomic molecules

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6
Q

What type of intermolecular forces exist between non-polar halogen molecules?

A

Weak van der Waals forces

These forces increase in strength as the relative molecular mass (RMM) increases.

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7
Q

What trend is observed in the physical state of halogens as the group is descended?

A

Gas to liquid to solid. Boiling point increases

This trend corresponds to increasing molecular mass.

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8
Q

How soluble are halogens in water?

A

Low solubility

Halogens are more soluble in non-polar solvents.

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9
Q

What is the solubility of Chlorine in water?

A

Soluble, forming a pale green/colourless solution

This solution is commonly referred to as ‘chlorine water’.

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10
Q

What is the solubility of Bromine in water?

A

Soluble, forming a yellow/orange/brown solution

This solution is known as ‘bromine water’.

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11
Q

What is the solubility of Iodine in water?

A

Virtually insoluble

Any solution formed is yellow/brown.

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12
Q

In what type of solution is Iodine soluble?

A

In a solution containing iodide ions

This forms a brown solution.

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13
Q

What is the solubility of Chlorine in hexane?

A

Soluble, forming a pale green solution

This highlights the compatibility of non-polar solvents.

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14
Q

What is the solubility of Bromine in hexane?

A

Soluble, forming an orange solution

Bromine’s solubility in hexane indicates its non-polar nature.

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15
Q

What is the solubility of Iodine in hexane?

A

Soluble, forming a purple solution

The color change in solution reflects iodine’s interactions with hexane.

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16
Q

What is the reaction of chlorine with water?

A

Cl2 + H2O → HClO + HCl

HClO is hypochlorous acid or chloric(l) acid.

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17
Q

What type of reaction occurs when chlorine reacts with water?

A

Disproportionation. Chlorine is oxidised from 0 to +1 and reduced from 0 to -1

One element is oxidized and reduced in the same reaction.

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18
Q

What are the oxidation states of chlorine in the reaction with water?

A

Chlorine is oxidized from 0 to +1 and reduced from 0 to -1.

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19
Q

What is the reaction of chlorine with cold dilute alkali (e.g., NaOH)?

A

2NaOH + Cl2 → NaCl + NaClO + H2O

The general ionic equation is: 2OH + Cl2 → Cl-+ ClO- + H2O.

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20
Q

What is the oxidation number of chlorine in chlorate(I)?

A

+1

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21
Q

What is the reaction of chlorine with hot concentrated alkali (e.g., NaOH)?

A

3Cl2 + 6NaOH → 5NaCl + NaClO3 + 3H2O

The general ionic equation is: 6OH + 3Cl2 → 5Cl- + ClO3- + 3H2O.

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22
Q

What is the oxidation number of chlorine in chlorate(V)?

A

+5

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23
Q

Does iodine react with cold dilute alkali?

A

No

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24
Q

What does iodine react with to form an iodate(V) compound?

A

Hot concentrated alkali

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25
What happens to chlorine in all these reactions?
Chlorine undergoes disproportionation
26
What color does the yellow-green gas form when dissolved?
Colorless solution (or pale green)
27
Is Cl2 an oxidising or reducing agent?
Oxidising agent as it wants to gain an electron
28
Is Cl- a reducing agent or an oxidising agent?
Reducing agent as it wants to lose its electron
29
What happens when a more reactive halogen is introduced to a solution of its halide ions?
It displaces a less reactive halogen from the solution Example: Cl2 + 2Br- → 2Cl- + Br2 changes the solution from colourless to orange.
30
What is the strongest oxidising agent among halogens?
Chlorine (Cl2) ## Footnote Chlorine is the easiest to get reduced.
31
What is the chemical equation that demonstrates chlorine acting as an oxidising agent?
Cl2 + 2I- → 2Cl- + I2 ## Footnote This reaction changes the solution from colourless to brown.
32
What does the oxidising power of a halogen measure?
The strength with which a halogen atom can gain an electron.
33
What causes the decrease in reactivity of halogens down the group?
Increase in atomic radius and shielding This results in decreased attraction between the incoming electron and the atomic nucleus.
34
What is the role of Cl2 in redox reactions?
Oxidising agent ## Footnote It gets reduced in reactions.
35
What is the role of iodide ions in redox reactions?
Reducing agent ## Footnote It wants to lose its electron and give it to another substance.
36
How does the reducing power of halide ions change down the group?
It increases ## Footnote Larger halide ions have outer electrons further from the nucleus, making them easier to lose.
37
What is an important distinction between oxidising power of halogens and reducing power of halides?
Do not confuse them; a reducing agent gets oxidised.
38
What happens when chloride reacts with concentrated sulfuric acid?
NaCl + H2SO4 → NaHSO4 + HCl ## Footnote This is not a redox equation; HCl has no reducing ability.
39
What are the observations when chloride reacts with concentrated sulfuric acid?
Misty fumes (HCl), heat released, gas produced, solid disappears, pungent smell (HCl).
40
What happens when bromide reacts with concentrated sulfuric acid?
Bromide ions reduce sulfur in H2SO4 from +6 to +4 in SO2 ## Footnote The reaction produces misty fumes (HBr), heat, gas, solid disappears, red-brown vapour (Br2), and a pungent smell (HBr/SO2/Br2)
41
What is the balanced equation for the reaction of NaBr with H2SO4?
NaBr + H2SO4 → NaHSO4 + HBr
42
What is the balanced equation for the reaction of 2HBr with H2SO4?
2HBr + H2SO4 → Br2 + SO2 + 2H2O
43
What are the observations when bromide reacts with concentrated sulfuric acid?
Misty fumes (HBr), heat released, gas produced, solid disappears, red-brown vapour (Br2), pungent smell (HBr/SO2/Br2) ## Footnote These observations indicate the occurrence of a chemical reaction.
44
What is the strongest reducing agent among the hydrogen halides?
HI
45
What happens when iodide reacts with concentrated sulfuric acid?
Iodide ions reduce sulfur in H2SO4 from +6 to +4 in SO2, to 0 in S, and -2 in H2S ## Footnote This indicates a strong reducing capability of iodide ions.
46
What is the balanced equation for the reaction of NaI with H2SO4?
NaI + H2SO4 → NaHSO4 + HI
47
What is the balanced equation for the reaction of 6HI with H2SO4?
6HI + H2SO4 → 3I2 + S + 4H2O
48
What is the balanced equation for the reaction of 8HI with H2SO4?
8HI + H2SO4 → 4I2 + H2S + 4H2O
49
What are the observations when iodide reacts with concentrated sulfuric acid?
Misty fumes (HI), heat released, gas produced, solid disappears, purple vapour and grey-black solid (I2), pungent smell (HI/SO2/I2), rotten eggs smell (H2S), yellow solid (S) ## Footnote These observations indicate the different products formed during the reaction.
50
How many unique equations need to be remembered for reactions involving bromide and iodide with concentrated sulfuric acid?
Four equations
51
What type of reactions occur when solid halide compounds react with concentrated phosphoric acid?
Acid-base reactions
52
What is the balanced equation for the reaction of NaCl(s) with H3PO4(l)?
NaCl(s) + H3PO4(l) → NaH2PO4(s) + HCl(g) This is the same for every halide
53
What are the observations when solid halide compounds react with concentrated phosphoric acid?
White steamy fumes of the hydrogen halides are evolved ## Footnote Testing with ammonia gas produces lots of white smoke.
54
What are the two treatments mentioned for killing microorganisms in drinking water?
Chlorine and ozone
55
What is ozone an allotrope of?
Oxygen ## Footnote Ozone is a triatomic form of oxygen (O3).
56
How can ozone be generated?
Using high voltage electricity or UV light 3O2 → 2O3
57
What reaction occurs when chlorine reacts with water?
Cl2 + H2O → HClO + HCl ## Footnote This reaction forms hypochlorous acid and hydrochloric acid.
58
List three advantages of using chlorine for water treatment.
* Cost effective * Provides residual protection * More soluble in water ## Footnote Residual protection means chlorine remains in the water when it reaches consumers.
59
What is a disadvantage of chlorine in drinking water?
Gives drinking water an unpleasant taste and smell ## Footnote Chlorine can also be toxic in higher doses.
60
What is one major advantage of using ozone over chlorine?
More effective at killing bacteria ## Footnote Ozone reacts better with natural organic matter.
61
What happens to the breakdown product of ozone in water treatment?
It becomes oxygen with no residual chemicals ## Footnote This results in no smell or taste in the water.
62
What is a disadvantage of using ozone for water treatment?
Higher costs ## Footnote Ozone treatment is generally more expensive than chlorine.
63
Fill in the blank: Ozone is _______ soluble in water than chlorine.
Less ## Footnote This affects the mixing techniques required for ozone.
64
True or False: Chlorine is safe for humans in any amount.
False ## Footnote Care must be taken to avoid over-chlorination.

Chemistry Unit 1 (9 decks)

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