4.2 Group 7 Elements

Question 1

give the name for group 7

Answer 1

halogens

Question 2

true or false: halogens are diatomic molecules

Answer 2

true

Question 3

colour change of I2 + and KBr (+give dispalcement)

Answer 3

No change (stays brown) [1]
because Br is more reactive than I [2]

Question 4

colour change of I2 + and KCl (+give dispalcement)

Answer 4

No change (stays brown) [1]
because Cl is more reactive than I [2]

Question 5

color change of Br2 + KI (+give displacement)

Answer 5

Yellow –> brown [1]
Bromine displaces iodine [2]

Question 6

colour change of Br2 + KCl (+ give displacement)

Answer 6

no change (stays yellow) [1]
because Cl is more reactive than Br

Question 7

colour change of Cl2 + KI (+give displacement)

Answer 7

colourless –> brown [1]
because Cl displaces iodine [2]

Question 8

colour change of Cl2 + KBr (+ give displacement)

Answer 8

Colourless –> yellow [1]
because Cl displaces Br [2]

Question 9

what colour does phlenolphthalein go in HCl (aq)

Answer 9

colourless

Question 10

what colour does methyl orange go in HCl (aq)

Answer 10

red

Question 11

what colour does damp blue litmus paper go in HCl (aq)

Answer 11

red

Question 12

what colour does damp red litmus paper go in HCl (aq)

Answer 12

stays red

Question 13

what colour does dry blue litmus paper go in HCl (aq)

Answer 13

red

Question 14

what colour does dry litmus paper go in HCl (aq)

Answer 14

stays red

Question 15

what colour does universal indicator go in HCl (aq)

Answer 15

red

Question 16

what colour does phlenolphalein go in HCl (aq)

Answer 16

stays colourless

Question 17

what colour does methyl orange go when HCl (g) is added

Answer 17

yellow

Question 18

what colour does damp blue litmus paper go when HCl (g) is added

Answer 18

red

Question 19

what colour does damp red litmus paper go when HCl (g) is added

Answer 19

stays red

Question 20

what colour does dry blue litmus paper go when HCl (g) is added

Answer 20

stays blue

Question 21

what colour does unviersal indicator paper go when HCl (g) is added

Answer 21

green

Question 22

what is the pH of HCl (g)

Answer 22

7

Question 23

why is it inadvisable to use pure liquid bromine

Answer 23

because it is highly toxic and corrosive

Question 24

in the equation 2KBr + Cl2 –> 2KCl + Br which ion or molecule has been reduced

Answer 24

Cl2 molecule, because it gains an electron

Question 25

what is the ionic equation of: 2K+ + 2Br- + Cl2 --> 2k+ + 2Cl- + Br2

Answer 25

2Br- + Cl2 --> 2Cl- +Br2

Question 26

in the equation 2KBr + Cl2 --> 2KCl + Br which ion or molecule has been oxidised

Answer 26

Br- ion because it loses an electron

Question 27

give the reactivity series of I2, Br2 and Cl2

Answer 27

Most reactive: Cl2 Br I2 Least reactive:

Question 28

give the general equation for reacting metal halides and halogens

Answer 28

metal halide (less reactive) + halogen (more reactive) --> metal halide (more reactive) --> halogen (less reactive)

Question 29

colour of I2 as aq

Answer 29

red-brown

Question 30

colour of I2 in organic solvent

Answer 30

purple

Question 31

colour of I2 as a solid

Answer 31

dark grey

Question 32

colour of Br2 as aq

Answer 32

orange

Question 33

colour of Br2 in an organic solvent

Answer 33

orange

Question 34

colour of As as a solid

Answer 34

black

Question 35

colour of Br2 as a solid

Answer 35

brown

Question 36

colour of Cl2 when aq

Answer 36

pale green, almost colourless

Question 37

colour of Cl2 in organic solvent

Answer 37

pale green

Question 38

colour of Cl2 when solid

Answer 38

pale green

Question 39

colour of Fl2 as a solid

Answer 39

pale yellow

Question 40

why are halogens sparingly soluble in water?

Answer 40

because they are non-polar molecules

Question 41

what type of compound is forme when group 7 elements reacts with metals?

Answer 41

metal halides

Question 42

what type of substances are group 7?

Answer 42

simple molecular

Question 43

why does reactivity decrease down group 7 [3 points]

Answer 43

because the no. of shells increase [1] and the force of attraction between the outermost shell and the nucleus decreases [2] so it's harder for the atom to gain anotehr electron [3]

Question 44

how is a halide formed? [3 points]

Answer 44

when a halogen reacts with another subtsance [1], gains an electron [2], and become a negative ion [3]

Question 45

state the difference between halogens and halides

Answer 45

halides have a 1- charge becayse they're ions

Question 46

what state is At2 at room temperature

Answer 46

s

Question 47

what state is I2 at room temperature

Answer 47

s

Question 48

what state is Br2 at room temperature

Answer 48

l

Question 49

what state is Cl2 at room temperature

Answer 49

g

Question 50

what state is Fl2 at room temperature

Answer 50

g

Question 51

give the physcial desription of At2 at room temperature [2 points]

Answer 51

black [1] solid [2]

Question 52

give the name of the element that spontaneously sublimes at room temp? also give the colour fo the gas it sublimes to. [2 points]

Answer 52

iodine [1]. sublimes to a purple [2] gas.

Question 53

give the physical description of iodine at room temperature? [3 points]

Answer 53

shiny [1] dark grey [2] solid [3]

Question 54

give the name of the only non-metallic element that is liquid at room temp.

Answer 54

Bromine

Question 55

what does Br2 do in fire reatardants?

Answer 55

reduces combustability

Question 56

what colour does damp blue litmus paper go when Cl2 is added and why? [2 points]

Answer 56

- (bleached) white - because Cl2 acts as a bleaching agent [2] and is highly soluble in water [3]

Question 57

what liquid is Cl2 highly soluble in

Answer 57

water

Question 58

give two common compounds in which chlorine is found

Answer 58

common table salt [1] and hydrochloric acid [2]

Question 59

what colour is F2 gas

Answer 59

pale yellow

Question 60

why does reactivity decrease as you go down group 7 [3 points]

Answer 60

more electrons shells [1], and the outer electrons are further from the nucleus [2] therefore the attraction between the +ve nucleus and the -ve electrons is weaker [3]

Question 61

are halogens toxic?

Answer 61

yes. most toxic of the non-metal elements

Question 62

what is Br2 used for

Answer 62

pesticides

Question 63

what is F2 used for

Answer 63

preventing tooth decay

Question 64

what is Cl2 used for

Answer 64

water purification

Question 65

what is iodine used for?

Answer 65

antiseptic

Question 66

when group 7 elements react with non-metals, what happens to the group 7 atoms in terms of electrons?

Answer 66

share electrons (simple covalent bonding)

Question 67

when group 7 elements react with metals, what happens to the group 7 atoms in terms of electrons?

Answer 67

gain 1 electron to acheive a full outer shell.

Question 68

define diatomic molecules

Answer 68

molecules made of 2 atoms

Question 69

give 3 physical properties of the halogens:

Answer 69

aftf: - non-metal - diatomic molecules - insulator of electricity - bp/mp increase as you go down the group - reactivity decrease as you go down the group

Question 70

do halogens get lighter or darker as you move down the group?

Answer 70

darker