4.3 HALOGENS Flashcards
What group are the halogens in
7
Why does the melting/boiling point of the halogens increase as you go down the group
- The molecules become larger
- So the intermolecular forces become stronger
- More energy is needed to overcome these intermolecular forces.
What is special about all the halogens molecular formular
They are all diatomic (have a 2 e.g Br2)
What type of structure are the halogens
Simple molecular substances, covalently bonded
What happens to the trend of colours of the halogens as you go down the group
They get darker as you go down
Formula, colour and state of fluorine
- F2
- Very Pale Yellow
- Gas
Formula, colour and state of Chlorine
- C2
- Pale Green
- Gas
Formula, colour and state of Bromine
- Br2
- Orange
- Liquid
Formula, colour and state of Iodine
- I2
- Dark Grey
- Solid
Formula, colour and state of Astatine
- At2
- Black
- Solid
What halogen is volatile
Bromine
What does iodine do easily
Sublime
What fumes does iodine release
Purple
What fumes does bromine release
Orange
When a halogen reacts with a metal, what compound is formed and how is it a redox reaction
An ionic compound. The halogen becomes reduced as it gains an electron, and the metal becomes oxidised as it loses an electron(s)
Define Halide Formation
When a halogen reacts with another substance, gains an electron and becomes a negative ion
What are the 3 properties of hydrogen halides
- Are all gases
- Dissolve easily in water
- Become strong acids
When halogens become halide ions, what happens to the ending of their names
It changes to ‘-ide’
For example: Chlorine → Chloride
Why do the halogens get less reactive as you go down the periodic table?
- As you go down the table
- The atoms get larger, so have more electron shells
- The outer shell of electrons, gets further away from the positive attraction of the nucleus
- And it’s shielded by more complete electron shells
- The further the outer shell of electrons is from the positive attraction of the nucleus, the harder it is to attract another electron to complete the outer shell as the attraction is weaker
- So the reactivity decreases the further you go down the group
Chemical test for chlorine
Damp blue litmus paper is turns white as it is bleached
What is the colour of hydrogen chloride
Colourless
What type of structure is hydrogen chloride
Simple molecular covalent structure
What state is hydrogen chloride at room temperature
Gas
What is dissociation
The separating of ions within H2O
How does dissociation work with hydrogen chloride
When the Halide is bubbled through water, the H+ ions and the CL- ions seperate
In water, what does Hydrogen Chloride (g) dissolve into
Hydrochloric Acid (Aq)
How is HCl(ag) acidic
The hydrogen ions dissociate, and the H+ ions present in the solution mean the solution is acidic
How come electricity can flow through through hydrochloric acid
- When the hydrogen chloride gas is bubbled through water, it dissociates, and becomes HCl (aq) which is hydrochloric acid.
- As the HCl(g) has dissociated, there are free ions in the solution that can carry charge and allows electricity to flow
What does hydrogen chloride form when dissolved in methlybezene
HCl (org) - It doesn’t dissociate
Why is HCl(org) in methylbenzene not acidic
The H+ ions from the Hydrogen Chloride don’t dissociate, and so there is no source of H+ ions
Why can’t HCl(org) in methylbenzene conduct electricity
The Hydrogen Chloride doesn’t dissociate, so there are no free ions in the solution to carry charge
What is the general equation for a halogen displacement (and give an example)
More reactive halogen + less reactive halide salt → less reactive halogen + more reactive halide salt
(Cl2 + KBr → Br2 + KCl)
What is the reactivity scale for the halogens, and so what does this mean regarding what halogen can displace the others
- Fluorine
- Chlorine
- Bromine
- Iodine
- Astatine
- Fluorine is the most reactive so can displace any, followed by chlorine displacing all but fluorine ect.
What is the colour of all halide salts
Colourless
What is the colour of chlorine in an aqueous solution
Colourless
What is the colour of bromine in an aqueous solution
Yellow
What is the colour of iodine in an aqueous solution
Brown
During a halogen displacement reaction, what does the colour change signify and why
The more reactive halogen displacing the other, as the halide salts are colourless. The halogen that is not part of the salt, is the new colour in an aqueous solution
What type of reaction are all halogen displacements
Redox - Something is being reduced, and something is being oxidised
In this halogen displacement reaction, what is being oxidised, and what is being reduced and why:
- Cl2(aq) + 2KBR(aq) → Br2(aq) + 2KCl(aq)
- Chlorine is being reduced as it is gaining an electron (when forming the halide salt)
- Bromine is being oxidised, as it is losing an electron (when being displaced, it loses the electron it was sharing with hydrogen)
