Topic 4 - Group 2 and 7

Question 1

what are the group 2 elements?

Answer 1

beryllium, magnesium, calcium, strontium and barium

Question 2

what is the trend of atomic radius down Group 2?

Answer 2

it increases, as one extra shell of electrons is added

Question 3

what is the trend of melting points down Group 2?

Answer 3

melting points decrease - as atomic size increases the metallic bonding weakens

Question 4

what is the trend of reactivity down Group 2?

Answer 4

it increases, because it is easier to remove the outer electron due to the increased distance

Question 5

what metal burns with a lilac flame?

Answer 5

potassium

Question 6

what metal burns with a red or blue flame?

Answer 6

rubidium

Question 7

what metal burns with a brick red flame?

Answer 7

calcium

Question 8

what metal burns with a green flame?

Answer 8

barium

Question 9

what metal burns with a red flame?

Answer 9

strontium

Question 10

what metal burns with a blue flame?

Answer 10

caesium

Question 11

what Group 2 metal reacts in steam?

Answer 11

magnesium

Question 12

what are the observations of Group 2 Metal + water?

Answer 12

effervescence, heating up, dissolving

Question 13

what do Group 2 metal react with cold water to form?

Answer 13

hydroxides

Question 14

what does magnesium react with steam to form?

Answer 14

magnesium oxide and hydrogen

Question 15

what does magnesium react with warm water to form?

Answer 15

magnesium hydroxide and hydrogen

Question 16

group 2 metal + oxygen -> ?

Answer 16

metal oxide

Question 17

group 2 metal oxide + water -> ?

Answer 17

hydroxides

Question 18

group 2 metal oxide + acid -> ?

Answer 18

salt and water

Question 19

describe the solubility trend down Group 2 hydroxides

Answer 19

they become more soluble down the group

Question 20

describe the solubility trend down Group 2 sulfates

Answer 20

they become less soluble down the group

Question 21

what is thermal decomposition?

Answer 21

the use of heat to break down a reactant into more than one product

Question 22

what do Group 2 carbonates decompose to?

Answer 22

group 2 oxides and CO2

Question 23

describe the thermal stability of Group 2 carbonates down the group

Answer 23

they become more thermally stable, because as the cations get bigger, they have less polarizing and distort the carbonate ion less

Question 24

describe the method of a flame test

Answer 24

1. use a nichrome wire
2. clean it by dipping it into concentrated hydrochloric acid then heating
3. dip wire in solid then put into flame

Question 25

describe the flame tests as proof of existence of ions

Answer 25

in a flame test the heat causes the electron to gain energy and move to a higher energy level. when it falls down due to the instability, it emits energy in the form of visible light (photons)

Question 26

what are the Group 7 elements?

Answer 26

fluorine, chlorine, bromine and iodine

Question 27

what is fluorine at room temperature?

Answer 27

pale yellow gas

Question 28

what is chlorine at room temperature?

Answer 28

light green gas

Question 29

what is bromine at room temperature?

Answer 29

red-brown liquid

Question 30

what is iodine at room temperature?

Answer 30

black solid, sublimes to purple gas

Question 31

what is the trend in melting/boiling points down Group 7?

Answer 31

increases down the group - as electrons are added, London forces get stronger - more energy required to break them

Question 32

what is the trend in electronegativity down Group 7?

Answer 32

decreases down the group - atomic radius increases due to the increasing number of shells - the nucleus is weaker and cannot attract the bonding pair

Question 33

what is the trend in reactivity down Group 7?

Answer 33

decreases - atoms get bigger - more shielding - harder to attract and accept electrons

Question 34

are halogens reducing or oxidising agents?

Answer 34

electron acceptor (forms -1 ions) o therefore oxidising agent

Question 35

what is the trend in oxidising strength down Group 7?

Answer 35

decreases down the group, it will displace the halogen below it from one of its compounds

Question 36

Cl2 + 2NaOH (cold and dilute) -> ?

Answer 36

NaCl (sodium chloride) + NaClO (sodium hypochlorite) + H2O

Question 37

Cl2 + NaOH (hot and concentrated) ->

Answer 37

NaCl + NaClO3 (sodium chlorate V) + H2O

Question 38

what is the trend in reducing agents down Group 7 halide salts?

Answer 38

increases, as ions get bigger it is easier for the outer electrons to be donated

Question 39

what is the test for halide ions?

Answer 39

nitric acid, then silver nitrate

Question 40

describe the method for halide ions test

Answer 40

1. acidify the solution using dilute nitric acid | 2. add a few drops of silver nitrate solution

Question 41

what does a white precipitate of silver halide show?

Answer 41

silver chloride

Question 42

what is the role of nitric acid in the silver nitrate halide test?

Answer 42

reacts with any carbonates present to prevent formation of silver carbonate

Question 43

what does a cream precipitate of silver halide show?

Answer 43

silver bromide

Question 44

what does a yellow precipitate of silver halide show?

Answer 44

silver iodide

Question 45

how are hydrogen halides produced?

Answer 45

sodium halide salts + phosphoric acid

Question 46

NaX +> H3PO4 -> ?

Answer 46

HX + NaH2PO4

Question 47

what is the observation when hydrogen halides are produced?

Answer 47

steamy fumes of the hydrogen halide, due to the halide meeting the air and dissolving in the moisture

Question 48

why is a downwards delivery tube used when producing hydrogen halides?

Answer 48

hydrogen halides are more dense than air and would settle at the bottom

Question 49

are hydrogen halides soluble in water, and if so, what do they form?

Answer 49

yes, acidic solutions

Question 50

describe the reaction of hydrogen halides with ammonia

Answer 50

HX + NH3 -> NH4X | white smoke

Question 51

how do you test for the presence of carbonate ions?(CO3 2-)

Answer 51

1. add a dilute acid 2. observe effervescence 3. bubble gas through limewater to test for CO2 (cloudy)

Question 52

how do you test for the presence of a sulfate?

Answer 52

1. acidified barium chloride (acid to cancel out carbonate) | 2. if present - white precipitate forms (barium sulfate)

Question 53

how do you test for ammonium ions? (NH4+)

Answer 53

1. add warm aqueous sodium hydroxide, forming ammonia | 2. pungent smell, turns damp red litmus paper blue