halogens Flashcards
State and explain the trend in boiling point of the halogens fluorine to iodine
Boiling point increase due to increase in electrons down the group. this increases the strength of the London forces and more energy is needed to break the intermolecular forces
how is fluorine found
A pale yellow gas
How is chlorine found
A pale green gas
How is bromine found
A brown liquid which evaporates to form a red/brown gas
How is iodine found
a dark grey solid which when warmed turns into a purple gas
As we go down the halogens, do the atoms get bigger or smaller and why
They get bigger due to more shells
As we go down the group are the halogens more or less volatile
They are less volatile
As we go down the group does electronegativity of the halogen increase or decrease?
It decreases because there is more shielding
How do halogens act in a reaction?
They gain electrons to form halide ions
So they are reduced and are oxidising agents
F has the highest oxidising power (most readily forms 1- ions)
How do halides act in a reaction?
They lose electrons to form halogens and are oxidised (are reducing agent) I has the highest reducing power
What is a displacement reaction?
When a more reactive (higher up) halogen reacts with a less reactive halide replacing it and a colour change occurs
Why is it better to use the non polar solvent cyclohexane to identify a displacement reaction instead of water?
In water bromine and iodine are hard to tell apart because bromine turns orange and iodine turns brown
What colour indicates chlorine or bromine left in the solution?
Pale Green or Orange
What colour indicates iodine left in the solution using water vs cyclohexane
Brown vs Violet
Write the full ionic and half equations of the displacement of chlorine and potassium bromide And explain what happened to the halogen and halide
Full equation: 2KBr + Cl2 -> 2kCl + Br2
ionic equation: 2Br- + Cl2 -> 2Cl- + Br2
half equations: Cl2 + 2e- -> 2Cl-
2Br- -> Br2 + 2e-
Chlorine has gained electrons, so they’re reduced to chloride ions (so halogens are oxidising agent)
Bromide ions lost electrons, so they have been oxidised to bromine atoms (So halide ions are reducing agents)
What is disproportionation
when the same element is both oxidised and reduced in the same redox reaction
Show the disproportion reaction between chlorine and water. What is made and why
Cl2 +H2O = HClO(aq) + HCl(aq)
0 +1 -1
This reversible reaction forms chloric 1 acid which is the chemical that kills bacterial so as usual drinking water in pools
In bright sunlight what could Happen instead of the disproportionation reaction of chlorine in water and what is the solution
2Cl2 +2H2O -> 4HCl + O2
So we use tinted windows
Show the disproportionation reaction between chlorine and sodium hydroxide. what is made and why
Cl2 + 2NaOH -> NaClO + NaCl + H2O
0 +1 -1
Sodium chlorate1 which is an active ingredient in bleach
What are the risks of chlorine And why do we still use it
chlorine is toxic; causes respiratory problems, irritation /burns on the skin, water contains a variety of organic compounds and chlorine reacts with these to form chlorinated hydrocarbons which form carcinogens – agent capable of causing cancer but this is outweighed by the benefit of fresh drinking water and therefore prevention of disease eg cholera which could eliminate whole populations.
Does reactivity increase or decrease down the group 7 halogen?
it decreases because of further outer electrons so less attraction so harder to gain an electron
Does first ionisation energy decrease or increase down group 7
Going down a group, the ionisation energy decreases. This is due to the increased shielding of the outer electrons from the nucleus and so the attraction is weaker and they are more easily removed.
what does v represent in chloric (v) acid
that The oxidation number of chlorine is five
Iodine and strontium react together. calcium reacts with bromine. Why is it hard to tell which reaction is more reactive
Strontium is more reactive than calcium but iodine is less reactive than bromine so is difficult to tell which effect is more dominant
