Group 7

Why are the halogens more soluble in cyclohexane than in water

- The halogens which are non polar molecules mix easily with cyclohexane, which is also non-polar. - easy mixing is possible where the intermolecular forces between solute and solvent molecules are about the same strength, the halogens and cyclohexane both form London forces which are similar in strength. - water is a polar substance and so can form hydrogen bonds that iodine can't

How do you show you have a solution of iodine

1) add an ORGANIC SOLVENT and shake the solution, halogens are more soluble in organic solvents, iodine will turn purple in the organic layer which is the upper layer because its less dense 2) Add starch and shake. Iodine will change from brown -> blue black

What is the problem in distinguishing between bromine and iodine solutions?

Both solutions can appear brown depending on the concentration of the solutions

State the solubility of chlorine, bromine and iodine in water

Cl2 - slightly soluble, Br2 - slightly soluble, I2 - slightly soluble

describe the reaction between hot iron and chlorine

Hot iron burns brightly in chlorine forming iron chloride

What happens to the intermolecular forces of the halogens as you go down the group and why

The London forces increase between the molecules due to the increasing number of electrons

Explain the trend in oxidising power of the halogens

The fewer the number of shells, the less shielded the electrons are from the nucleus. The attraction of the electrons to the nucleus is therefore stronger and the atom is likely tp accept electrons

Explain the trend in reducing power of the halides

The more electron shells, the more shielding of the nucleus and the outer electrons become less strongly held. Therefore they are lost more easily and the halide ion is more readily oxidised

How do displacement reactions between halogens and halide ions work?

The more reactive halogens (the strongest oxidising agents) will displace the more reactive halides (the strongest reducing agents) from solutions of their ions I.e. chlorine will displace bromide and iodide ions from solution

Iodine reacts with metals to form...

covalent halides

What colour and state is iodine in pure form

dark grey solid

What colour and state is bromine in pure form

dark red/ brown LIQUID

Trend of oxidising power of halogens

decreases down a group, fluorine being a very strong oxidising agent and iodine mild

Trend of reducing power of halides

increases down group, iodide is a good reducing agent and fluoride is a very poor reducing agent

Why does iodine form a brown precipitation if excess KI is present

iodine reacts with the iodide ions to from trioxide ions which give the solution its brown colour

Chlorine and bromine react with S block metals to form...

ionic halides

Why is fluorine not used in laboratories

it is too dangerous

Uses of bromine

make flame retardants, medicines and dyes

uses of chlorine

manufacture of PVC, kill bacteria in drinking water, bleach paper + textiles

uses of iodine

medicines, dyes and catalysts

the larger the molecules the ... polarisable

more

What is observed in the reaction: Cl2(g) + 2Br(aq) -> 2Cl-(aq) + Br2(aq)

orange colour will appear in solution on adding chlorine

Bromine colour in non-polar solvents

orange solution

What colour and state is chlorine in pure form

pale green GAS

What colour and state is flouring in pure form

pale yellow gas

Iodine colour in non-polar solvents

purple solution

what is electronegativity?

the ability of an atom to attract electrons in a covalent bond

Why does the electronegativity of group 7 decrease down the group

the atomic radius increases and so the shielding increases so the electrons in the covalent bond are further from the nucleus and are therefore less strongly attracted to the nucleus

Uses of flourine

the manufacture of the very slippery, non-stick polymer poly(tetraflourethene)

What happens to the melting and boiling temps as you go down group 7

they become higher

How are the halogens oxidising agents

they can accept electrons and get reduced

Are the halogens volatile

yes