3.2 Inorganic Chemistry: .3 Group 7, the halogens

Question 1

what is the trend in atomic radius down the group 7 elements?

Answer 1

the atoms gets bigger going down the group because each element has one extra filled main level of electrons compared with the one above it

Question 2

what is electronegativity?

Answer 2

the tendency of a atom to attract the pair of electrons in a covalent bond

Question 3

what is the trend in electronegativity going down the group 2 elements?

Answer 3

-there is a decrease in electronegativity -as the atoms get larger they become less electronegative -this is because the electrons are further away from the nucleus and are more shielded.

Question 4

what is the trend in melting/boiling point down the group 2 elements?

Answer 4

-the melting point increases as you down the group -this is because larger atoms have more electrons (higher electron density) -this means that the Van der Waals forces are greater and stronger

Question 5

the lower the boiling point the more ________ the element.

Answer 5

the lower the boiling point the more volatile the element

Question 6

what is the trend in oxidising ability down the group 2 elements?

Answer 6

-the elements become less oxidising down the group -this is because as you go down the group the elements become less reactive -this is because the atoms get larger as you go down the group meaning that the outer shell is further away from the nucleus -so electrons are less strongly attracted to it

Question 7

when will a halogen displace a halide iron?

Answer 7

if the halide is below it in the periodic table -so if the halogen is more reactive than the halide

Question 8

when an atom gains an element to become a negative ion what do you call it?

Answer 8

-the element is an oxidising agent -this is because it oxidises the other elements (causes other elements to lose an electron) -and it self is reduced because it has gained an electron (RIG- reduction is the gain of electrons)

Question 9

what is the original colour of chlorine?

Answer 9

very pale green

Question 10

what is the original colour of Bromine?

Answer 10

orange/brown solution

Question 11

what is the original colour of Iodine?

Answer 11

brown

Question 12

give the ionic equation for when Bromine reacts with Potassium iodide and state what you would see.

Answer 12

2KI + Br2 —> 2KBr + I2 -a brown solution is formed (I2)

Question 13

what halide ion does Fluorine displace?

Answer 13

-Chloride -Bromide - -Iodide

Question 14

what halide ion does Chlorine displace?

Answer 14

-bromide -iodide

Question 15

what halide ion does Bromine displace?

Answer 15

-Iodide

Question 16

what halide ion does Iodine displace?

Answer 16

-non

Question 17

give the ionic equation for when Chlorine reacts with Potassium bromide and state what you would see.

Answer 17

-2KBr + Cl2 —> 2KCl + Br2 an orange solution is formed (Br2)

Question 18

give the ionic equation for when Chlorine reacts with Potassium iodide and state what you would see.

Answer 18

-2KI + Cl2 —> 2KCl + I2 -a brown solution is formed(I2)

Question 19

When potassium iodide and Potassium bromide are formed they both produce brown solutions. how can you tell the distinguish between the two solutions?

Answer 19

• you add an organic solvent (Hydrogen peroxide H2O2)
• Bromine produces a brown solution
• iodine produces a violet solution

Question 20

what is the trend in the reducing power of halide ions? state why

Answer 20

• the reducing power of halide ionsm increases down the group
• this is because the reducing power of the halogen depends on how well it can lose an electron on its outer shell
• as you go down the group the atoms increase in size which means that the outer electron that needs to be lost is further away from the nucleus
• the outer electron is shielded from the attraction of the nucleus
• This means that the electron is easier to remove

Question 21

what is the relationhsip between reducing power and reactivity?

Answer 21

the greater the reducing power, the greater the reactivity and the faster the reduction takes place

Question 22

out of the halogens, which ones reduces Sulphuric acid?

Answer 22

Bromine and Iodine

Question 23

when reacting halides with concentrated sulphuric acid what state is the halide compound always in?

Answer 23

SOLID

(*so if you see a question like: what is the test for solid NaF then its using hydrochloric acid!!)

Question 24

How would you test for solid NaF? (create a eqaution)

state what the observations in the reaction would be

state whether it is a redox reaction

state what the H₂SO₄ acts as in this reaction

Answer 24

• you would add sulfuric acid e.g
• NaF_(s) + H₂SO_4(aq) –> HF_(g) + NaHSO_4(s)
• you would see misty white fumes produced by the Hydrogen Fluoride
• It is not a redox reaction
• The H₂SO₄ acts as an acid in this reaction.

Question 25

How would you test for solid NaCl? (create a eqaution) state what the observations in the reaction would be state whether it is a redox reaction state what the H2SO4 acts as in this reaction

Answer 25

- you would add sulfuric acid e.g - NaCl(s) + H2SO4(aq) --\> HCl(g) + NaHSO4(s) - you would see misty white fumes produced by the Hydrogen Chloride - It is not a redox reaction - The H2SO4 acts as an acid in this reaction.

Question 26

How would you test for solid NaBr? (create a eqaution) and what other reactions could take place? state what the observations in each reaction would be state whether they are redox reaction state what the H2SO4 acts as in the reactions

Answer 26

- you would add sulfuric acid e.g - NaBr(s) + H2SO4(aq) --\> HBr(g) + NaHSO4(s) - you would see misty white fumes produced by the Hydrogen Bromide - It is not a redox reaction - The H2SO4 acts as an acid in this reaction. - There could be another reaction: 2HBr(g) + H2SO4(aq) --\> SO₂ + Br₂ + 2H₂O (in this reaction you produce ROW= R: reduction product, O: oxidation product (always the halOgen), W: water) -for this second reaction you would observe, choking gas (SO2)and orange/brown vapour (Br2) the second reaction is a redox

Question 27

Hydrogen Bromide reacts with sulphuric acid -give the full balanced eqaution for the reaction and state what you would observe

Answer 27

2HBr(g) + H2SO4(aq) --\> SO2(g) + Br2(g) + 2H2O(l) (in this reaction you produce ROW= R: reduction product, O: oxidation product (always the halOgen), W: water) -in this reaction you would observe, choking gas (SO2)and orange/brown vapour (Br2) this is a redx reaction

Question 28

How would you test for solid NaI? (create a eqaution) and what other reactions could take place? state what the observations in each reaction would be state whether they are redox reaction state what the H2SO4 acts as in the reactions

Answer 28

- you would add sulfuric acid e.g - NaI(s) + H2SO4(aq) --\> HI(g) + NaHSO4(s) - you would see misty white fumes produced by the Hydrogen Iodide - It is not a redox reaction - The H2SO4 acts as an acid in this reaction. - There could be another reaction: 2HI(g) + H2SO4(aq) --\> SO2 + I2 + 2H2O (in this reaction you produce ROW= R: reduction product, O: oxidation product (always the halOgen), W: water) -for this second reaction you would observe, choking gas (SO2)and purple gas/black solid (I₂) the second reaction is a redox -there could be another reaction: 6HI + H₂SO₄ --\> S+ 3I₂ + 4H₂O you would observe a yellow solid (S), a purple gas/black solid (I₂) this is a redox reactoon -there could be another reaction: 8HI + H₂SO₄ --\> H₂S+ 4I₂ + 4H₂O you would observe bad egg smell (H₂S) and a purple gas/black solid (I₂)

Question 29

Hydrogen iodide reacts with sulphuric acid to form SO₂ -give the full balanced eqaution for the reaction and state what you would observe

Answer 29

2HI(g) + H2SO4(aq) --\> SO2 + I2 + 2H2O (in this reaction you produce ROW= R: reduction product, O: oxidation product (always the halOgen), W: water) -for this second reaction you would observe, choking gas (SO2)and purple gas/black solid (I2) this reaction is a redox

Question 30

Hydrogen iodide reacts with sulphuric acid to form Sulphur -give the full balanced eqaution for the reaction and state what you would observe

Answer 30

6HI + H2SO4 --\> S + 3I2 + 4H2O you would observe a yellow solid (S) and a purple gas/black solid (I2) this is a redox reactoon

Question 31

Hydrogen iodide reacts with sulphuric acid to form H2S -give the full balanced eqaution for the reaction and state what you would observe

Answer 31

8HI + H2SO4 --\> H2S+ 4I2 + 4H2O you would observe bad egg smell (H2S) and a purple gas/black solid (I2)

Question 32

when testing for halides with silver nitrate what state is the halide compound always in?

Answer 32

solution as a precipitate is formed and for a precipitate to be formed you need two solutions (\*remember\* the state symbol for the ion or compound is going to be aqueous)

Question 33

how would you test for aqueous Fluoride? give the ionic eqaution for the reaction and state what you'd observe.

Answer 33

- You would first add dilute nitric acid to remove any ions which might interfere with the test - Then you add silver nitrate to the solution - you would just see a colourless solution, no precipitate is formed as no reaction takes place (FIND OUT) Ag+(aq) + F-(aq) --\> AgF(aq)

Question 34

how would you test for aqueous Chloride? give the ionic eqaution for the reaction and state what you'd observe.

Answer 34

- You would first add dilute nitric acid to remove any ions which might interfere with the test - Then you add silver nitrate to the solution - you would see a white precipiate Ag+(aq) + Cl-(aq) --\> AgCl(s)

Question 35

how would you test for aqueous Bromide? give the ionic eqaution for the reaction and state what you'd observe.

Answer 35

- You would first add dilute nitric acid to remove any ions which might interfere with the test - Then you add silver nitrate to the solution - you would see a cream precipiate Ag+(aq) + Br-(aq) --\> AgBr(s)

Question 36

how would you test for aqueous Iodide? give the ionic eqaution for the reaction and state what you'd observe.

Answer 36

- You would first add dilute nitric acid to remove any ions which might interfere with the test - Then you add silver nitrate to the solution - you would see a yellow precipiate Ag+(aq) + I-(aq) --\> AgI(s)

Question 37

out of the halide ions which forms a precipitate with silver ions the fastest?

Answer 37

Iodide

Question 38

out of the halide ions which forms the precipitate with silve ions tthe slowest?

Answer 38

chloride

Question 39

to be extra sure you can test your results (from testing halide ions with silver nitrate) with ammonia solution. (\*remember\*: this is only used on the precipitates so fluorine cant be tested with ammonia since it did not form a precipitate)

Answer 39

You might do this because the colour variations are pretty similar betweent the halide ions so this distinguishes them more

Question 40

what is the effect of Concentrated and dilute ammonia solutions on silver chloride precipitate?

Answer 40

they both dissolve the Silver Chloride -so it is soluble in both solutions

Question 41

what is the effect of Concentrated and dilute ammonia solutions on silver bromide precipitate?

Answer 41

the dilute ammonia solution does not dissolve the silver bromide but the concentrated does -so silver bromide is insoluble in dilute ammonia solution but in soluble in concentrated ammonia solution

Question 42

what is the effect of Concentrated and dilute ammonia solutions on silver iodide precipitate?

Answer 42

silver iodide does not dissolve in niether of the solutions -so silver iodide is insoluble in both concentrated and dilute ammonia solutions (\*remember\*: I I I, iodine is insoluble)

Question 43

give the eqaution where common household bleach is produced in this reaction chlorine is both oxidised and reduced, what is this called?

Answer 43

2NaOH(aq) + Cl2(g) --\> NaClO(aq) + NaCl(aq) + H2O(l) the NaClO is your bleach disproportionation

Question 44

what is called when a elements is both reduced and oxidised in a reaction?

Answer 44

disproportionation

Question 45

give the ionic eqaution for when chlorine is mixed with water producing chlorate and chloride ions why is this reaction used for the safety of swimming pools?

Answer 45

Cl2(g) + H2O(l) \<--\> 2H+(aq) + Cl-(aq) + ClO- (aq) chlorate ions (ClO-) kill bacteria

Question 46

give the symbol eqaution for when chlorine reacts with water in sunlight

Answer 46

Cl2(g) + 2H2O \<---\> 4H+(aq) + 2Cl- + O2

Question 47

what are uses of chlorine in water treatment?

Answer 47

- kills disease causing microorganisms - some chlorine persists in the warer and prevents reinfection further down the supple - it prevents the growth of algae, eliminating bad tatses and smells, and discoulouration caused by organic compounds

Question 48

what are the risks that arise from using chlorine to treat water

Answer 48

- chlorine gas is very harmful it it's breather in- it irritates the respiratory system - liquid chlorine can cause severe chemical burns on skin and eyes - water contains a variety of organic compounds, chlorine reacts with these compounds to form chlorinated hydrocarbons e.g chloromethane many of these chlorinated hydrocarbons are carcinogenic (however increased cancer risk is small compared to the risk from untreated water)