inorganic chemistry and the periodic table

Question 1

why does ionisation energy decrease down group 2?

Answer 1

-electron shells of elements increase by 1 down G2
-extra inner shells shield outer electrons from attraction of positive nucleus
-atomic radius increases=outer electrons further away from nucleus=reduction in electrostatic attraction
-these factors make it easier to remove outer electrons∴ionisation energy decreases

Question 2

does the increase in positive charge of the nucleus (due to extra protons) affect ionisation energy of group 2 elements?

Answer 2

no, effect is overridden by extra shells

Question 3

what is the trend in reactivity down group 2?

Answer 3

increases down the group

Question 4

what is the trend in ionisation energy down group 2?

Answer 4

decreases down the group

Question 5

why does reactivity increase down group 2?

Answer 5

elements of G2 react by losing outer 2 electrons ∴ higher ionisation energies makes it more difficult to lose the outer 2 electrons ∴ will be less reactive

Question 6

what happens when a group 2 metal reacts with water?

Answer 6

forms a metal hydroxide and hydrogen
Ca + 2H₂O→Ca(OH)₂ + H₂

Question 7

How does Be react with water?

Answer 7

doesn’t react

Question 8

How does Mg react with water?

Answer 8

very slowly

Question 9

How does Ca react with water?

Answer 9

steadily

Question 10

How does Sr react with water?

Answer 10

fairly quickly

Question 11

How does Ba react with water?

Answer 11

rapidly- effervescence

Question 12

what happens when a group 2 metal burns in oxygen?

Answer 12

solid white oxide formed
2Ca + O₂→2CaO

Question 13

what happens when a group 2 metal reacts with chlorine?

Answer 13

forms solid white chlorides
Ca + Cl₂ → CaCl₂

Question 14

what are the oxides and hydroxides of group 2?

Answer 14

bases

Question 15

what happens when oxides and hydroxides of group 2 react with dilute acids?

Answer 15

they neutralise the dilute acids because they are bases,, also form solutions for corresponding salts

Question 16

what happens when oxides and hydroxides of group 2 react with water?

Answer 16

form alkaline solutions,, more alkaline as you go down the group

Question 17

why do oxides form more strongly alkaline solutions as you go down the group?

Answer 17

the hydroxides get more soluble

Question 18

what is the trend in solubility of group 2 hydroxides (and other singly charged ions) down the group?

Answer 18

increased solubility

Question 19

what is the trend in solubility of group 2 doubly charged negative ions (e.g. SO₄²⁻ sulfates) down the group?

Answer 19

decrease solubility

Question 20

is barium sulfate completely insoluble?

Answer 20

yes

Question 21

what substance helps detect carbonate ions and hydrocarbonate ions?

Answer 21

HCl

Question 22

what happens when HCl and CO₃²⁻/HCO₃⁻ react?

Answer 22

they fizz and give off CO₂
CO₃²(s) + 2H⁺(aq) → CO₂(g) + H₂O(l)

Question 23

how can you test for CO₂?

Answer 23

lime water goes cloudy

Question 24

how do you test for sulfates?

Answer 24

HCl and Barium Chloride

Question 25

how do you identify a sulfate ion?

Answer 25

-add dilute HCl followed by Barium chloride solution -if white participate of barium sulfate forms it means the original compound contained a sulfate

Question 26

why is HCl added in the test for sulfate ions?

Answer 26

to get rid of traces of carbonate ions so they don't affect results

Question 27

how to test for ammonium compounds?

Answer 27

-damp red litmus paper -because ammonia gas (NH₃) is alkaline it will turn the red litmus paper blue

Question 28

how to test for ammonium ions (NH₄⁺)?

Answer 28

-add sodium hydroxide to unknown substance into a test tube and gently heat the mixture -if ammonia is given off NH₄⁺ ions are present -this can be tested using damp litmus paper

Question 29

why does litmus paper need to be damp when testing for ammonia gas?

Answer 29

so the gas can dissolve and make the colour change

Question 30

why is beryllium oxide an exception from the oxides of the group 2 metals?

Answer 30

it does not react with water

Question 31

what happens when oxides of group 2 are with water?

Answer 31

they react readily and form soluble metal hydroxides that are very alkaline due to the OH⁻

Question 32

why is magnesium oxide an exception from the oxides of the group 2 metals?

Answer 32

reacts slowly and the hydroxide formed is not very soluble

Question 33

what is thermal decomposition?

Answer 33

when a substance breaks down when heated

Question 34

the more thermally stable a substance is.....

Answer 34

the more heat it will take to break it down

Question 35

what colour will the reaction mixture turn if bromine is displaced?

Answer 35

orange

Question 36

what colour will the reaction mixture turn if iodine is displaced?

Answer 36

brown

Question 37

how else can you see the results of a halide-halogen redox reaction?

Answer 37

by shaking the mixture with hexane (organic solvent) so halogen will dissolve and settle as a distinct layer above aqueous solution

Question 38

how is chlorine used in water treatment to kill bacteria?

Answer 38

-mixing chlorine and water is a disproportionation reaction which produces HCl and HClO(hypochlorous acid) -HClO ionises to make chlorate ions which kill bacteria in water

Question 39

flame colour Li?

Answer 39

red

Question 40

flame colour Na?

Answer 40

orange/yellow

Question 41

flame colour K?

Answer 41

lilac

Question 42

flame colour Rb?

Answer 42

red

Question 43

flame colour Cs?

Answer 43

blue

Question 44

flame colour Ca?

Answer 44

brick-red

Question 45

flame colour Sr?

Answer 45

crimson

Question 46

flame colour Ba?

Answer 46

green

Question 47

why do the flames colour of group 1 and 2 elements vary?

Answer 47

-energy absorbed from flame causes electrons to move to higher energy levels -colour seen as electron falls back to lower energy level releasing energy in the form of light -difference in energy between higher and lower levels determines wavelength of light released (determines colour of light)

Question 48

why does thermal stability of carbonates and nitrates increase down groups 1 and 2?

Answer 48

As the positive ions get larger down the group, they affect on the carbonate ions near them less. More heat must be supplied for the carbon dioxide to leave the metal oxide.

Question 49

halogen + group 1/2 metal?

Answer 49

halide salt

Question 50

how are halide salts formed?

Answer 50

halogen oxidises group 1/2 metals (halogen reduced itself)

Question 51

why should reactions involving halogens be carried out in a fume cupboard?

Answer 51

halogens are toxic

Question 52

what happens when a cold alkali reacts with a halogen?

Answer 52

disproportionation reaction (halogen is simultaneously reduced and oxidised)

Question 53

how is bleach formed?

Answer 53

disproportionation reaction with Cl2 gas + cold dilute aqueous 2NaOH NaCl also formed and water

Question 54

what is the chemical name for bleach?

Answer 54

sodium chlorate I (NaClO)

Question 55

what is the trend in reducing power for the halides? (halogen ions)

Answer 55

reducing power decreases down the group because= -ions get bigger down the group=electrons further away from nucleus=attraction gets weaker=electron is lost easily -there are extra inner electron shells so shielding effect is greater

Question 56

what happens in the reaction of KF/KCl with sulfuric acid?

Answer 56

-HF/HCl produced, misty fumes -Fluoride and chloride ions are not strong enough reducing agents to reduce sulfuric acid so reaction stops -not a redox reaction

Question 57

what happens in the reaction of KBr with sulfuric acid?

Answer 57

-HBr formed (first step),, misty fumes -HBr further reduces sulfuric acid (as it is a stronger oxidizing agent) into Br₂+SO₂+H₂O (second step),, orange fumes of bromine released,,redox reaction

Question 58

are halide ions reduced or oxidised in their reactions with H₂SO₄?

Answer 58

oxidised, they lose electrons and become positive

Question 59

what happens in the reaction of KI with sulfuric acid?

Answer 59

-HI formed (first step) -HI reduces H₂SO₄ into I₂+SO₂+H₂O -iodine ions are strong reducing agents so further reduce SO₂ to H₂S which smells of rotten egg

Question 60

why are iodine ions the strongest reducing agents?

Answer 60

because iodine ions reduces sulfur in H₂SO₄ from +6 to 0,,,, Br goes from +6 to +4

Question 61

what happens when hydrogen halides gases dissolve in water?

Answer 61

they become acids as hydrogen halides are acidic gases e.g. hydrogen chloride to hydrochloric acid

Question 62

what happens when a hydrogen halide reacts with ammonia gas?

Answer 62

white fumes produced forming NH₄Cl

Question 63

What to halide ions react with to form precipitate which is a test for halides?

Answer 63

silver nitrate solution AgNO₃

Question 64

what is the hazard of silver nitrate?

Answer 64

corrosive

Question 65

what precipitate is formed in the silver nitrate test for fluoride?

Answer 65

there is no precipitate as AgF is soluble

Question 66

what precipitate is formed in the silver nitrate test for chloride?

Answer 66

white (milk)

Question 67

what precipitate is formed in the silver nitrate test for bromide?

Answer 67

cream (cream)

Question 68

what precipitate is formed in the silver nitrate test for iodide?

Answer 68

yellow (butter)

Question 69

How can you further tell what halide has been identified from silver nitrate test if precipitates look similar?

Answer 69

add ammonia solution Silver chloride (AgCl) dissolves in dilute ammonia. Silver bromide (AgBr) dissolves in concentrated ammonia but not in dilute. Silver iodide (AgI) is insoluble in ammonia.

Question 70

what happens when ammonia solution is added to AgCl precipitate?

Answer 70

precipitate dissolves in dilute ammonia solution to make colourless liquid

Question 71

what happens when ammonia solution is added to AgBr precipitate?

Answer 71

only dissolves in concentrated ammonia solution to give colourless solution (would not happen in dilute)

Question 72

what happens when ammonia solution is added to AgI precipitate?

Answer 72

doesn't dissolve at all regardless of concentration