halgogens and redox

What are the states of halogens at room temperature and what's the trend in their boiling point?

-F: gas

-Cl gas

-Br liquid

-I solid (violet)

-boiling point increases as size of molecule and number of electrons increases 

-so there are stronger intermolecular (induced dipole) forces 

-more energy required to break forces

halogen preoperties

-simple molecular structure

-coloured vapours

-poor conductors of heat and electricity

-low melting and boiling points 

trend in reactivity

-decreases as you descend

-shielding and atomic radius increase

-so nuclear attraction to outer electron decreases

-despite nuclear charge increasing

-so electron can be gained less easily

-to form a halide ion

Which halogen is the strongest oxidising agent?

-chlorine

-can be reduced/ gain electrons most easily

What are rules for assigning oxidation numbers?

-it's 0 for atoms in uncombined elements

-the sum of oxidation numbers in neutral elements is 0

-in ions, sum of oxidation numbers equals to charge on ion

-the more electronegative atom has the negative oxidation number and the less electronegative had the positive oxidation number

What's the equation for chlorine to make a disinfectant and what type of reaction is it?

-Cl2 + H20 => HCl + HClO

-disproportionation reaction

-used to kill waterborne pathogens 

disproportionation reaction

-an element is simultaneously oxidised and reduced

What's the equation for making bleach?

-Cl2 + 2NaOH (cold) => NaClO + NaCl + H2O

-sodium chlorate (I) systematic name

-disinfects kitchen surfaces by killing germs

oxidation number of oxygen

-2 except in peroxides (H2O2) which is -1 and F2O which is +2

Oxidation number of hydrogen 

+1 except in hydrides (-1) e.g. CH4

chlorine oxidation number

-1 except in compounds with oxygen or fluorine because they're the most electronegative

solubility of nitrates

all soluble

solubility of potassium, sodium and ammonium salts

all soluble

solubility of chloride

all soluble except silver and lead (e.g. AgCl)

solubility of sulfates

all soluble except barium calcium silver and lead

solubility of carbonates

All insoluble except sodium potassium and ammonium carbonates

chloride ion test

-add silver nitrate

-white ppt

-soluble in dilute ammonia

bromide ion test

-add silver nitrate

-cream ppt

-soluble in conc ammonia

iodide ion test

-add silver nitrate

-yellow ppt

-insoluble in conc ammonia

What should you do before the silver nitrate halide ion test?

Add dilute nitric acid to remove carbonates

CO3 2- +2H+ => CO2 + H2O

oxidising agents

-a substance that has the ability to oxidize other substances and in the process gain electrons (be reduced)

colour of chlorine in water/aqueous solution

yellow

colour of bromine in water

orange

colour of iodine in water

brown

colour of chlorine in cyclohexane/organic solution

pale yellow

colour of bromine in cyclohexane

yellow

colour of iodine in cyclohexane

pink

What's made when chlorine reacts with hot sodium hydroxide?

-3Cl2 + 6NaOH => NaClO3 + 5NaCl + 3H2O

-sodium chloride (V) instead of (I) (NaClO) is formed

-oxidation number of chlorine from 0 to +5 and -1

How does the silver nitrate precipitate reaction work

-silver nitrate and sodium chloride are soluble in water so their ions are separated by water molecules 

-silver chloride is insoluble so ions stick together, can't be kept apart by water molecules

benefits and risks of chlorine in water treatment

kills bacteria/microorganisms/pathogens

toxic (chlorine gas), formation of chlorinated hydrocarbons

NaBrO3 name

-sodium bromate (V)

-oxidation numbers;

-Na; +1

-O3'; 2-

-Br +5

chlorine+ water

Cl2 + H2O > HCl + HClO

for water treatment

both acidic products