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halogens Flashcards

1
Q

appearance and state F2 at room temp

A

yellow gas
very reactive
toxic

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2
Q

appearance and state of Cl2 room temp and pressure

A

green gas
very reactive
toxic

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3
Q

appearance and state Br2 room temp and pressure

A

orange liquid
very reactive
toxic

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4
Q

appearance and state I2 room temp and pressure

A

grey crystal
reactive
toxic

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5
Q

trend of atomic radii of halogens

A

increases down the group

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6
Q

trend of electronegativity of halogens

A

decreases down the group

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7
Q

reactivity trend of halogens

A

decreases down the group

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8
Q

colour of Cl dissolved in solution

A

pale green

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9
Q

colour of Br dissolved in solution

A

orange

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10
Q

colour of I dissolved in water

A

brown

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11
Q

colour of I dissolved in cyclohexane

A

purple

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12
Q

distinguishing between bromine and iodine solution (both brown/orange solution)

A

add cyclohexane and shake -> iodine purple layer
add starch -> iodine blue black

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13
Q

reactions of halogens with iron (II) solution

A

place 2cm3 of Fe2+ into a test tube
add aqueous (chlorine)
until a change is observed

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14
Q

observation adding Fe2+ to Cl

A

turns pale yellow

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15
Q

observation on adding Fe2+ to Br

A

solution turns pale yellow

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16
Q

does I2 react with Fe2+

A

no

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17
Q

overall equation Cl2 + 2Fe2+
(same for Br2)

A

Cl2 + 2Fe2+ —> 2Fe3+ + 2Cl-

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18
Q

reaction of halogens and halides

A

add Cl water dropwise to 1cm3 of KBr solution and mix
repeat with Cl water and KI
replace Cl water with Br water and repeat with all halides

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19
Q

result of Cl with KBr

A

colourless solution turns pale yellow
hexane turns red

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20
Q

result of Cl with KI

A

colourless solution turns orange/brown
hexane turns purple

21
Q

result of Br with KI

A

turns dark orange
starch turns blue/black

22
Q

what should you add if you have difficulty interpreting results of Cl water and halides

A

1cm3 of organic solvent (hexane)

23
Q

reaction of halogens with cold alkali

A

2cm3 samples of each of the halogens in water
add a few drops of 0.4m NaOH
observe colour changes

24
Q

halogens in order of oxidising ability

A

least I2 Br2 Cl2 most

25
Q

why is Cl the most oxidising

A

Cl has the fewest electron shells with the least shielding and smallest radius
has the strongest ability to attract the electron from I or Br

26
Q

define disproportionation reaction

A

simultaneous oxidation and reduction of an atom of the same element in an ion or molecule

27
Q

reaction of halogens with cold alkali

A

2cm3 samples of each of the halogens in water
add a few drops of 0.4m NaOH
observe any colour changes

28
Q

observation of halogens on adding NaOH

A

turn colourless

29
Q

Cl2 + 2NaOH —>

A

NaCl + NaClO + H2O

(same for Br and I)

30
Q

3Cl2 + 6NaOH —>

A

5NaCl + NaClO3 + 3H2O

(same for Br and I)

31
Q

HCl + H2O —>

A

HCl + H+ + Cl-

32
Q

NH3 + HCl —>

A

NH4Cl

(same for I and Br)

33
Q

what does HCl gas appear as

A

steamy fumes

34
Q

which is the strongest reducing agent out of the halides

35
Q

why is I- the strongest reducing agent

A

it loses electrons most easily

36
Q

reaction of concentrated H2SO4 with potassium halides

A

spatula of potassium halide in a test tube
add 2/3 drops of conc H2SO4
test the gases evolved with conc NH3 on a glass rod, acidified dichromate paper, damp blue litmus paper and bubbling through silver nitrate solution

37
Q

what does acidified dichromate paper test for

38
Q

what does damp blue litmus paper test for

A

acidic gas

39
Q

displacement reaction H2SO4 + NaCl

A

H2SO4 + NaCl —> NaHSO4 + HCl

40
Q

redox displacement reaction between potassium bromide (or iodide) with conc H2SO4

A

KBr + H2SO4 —> KHSO4 + HBr

41
Q

test for halide ions

A

1cm3 of halide solution
3 drops dilute nitric acid
5 drops silver nitrate solution
add dilute ammonia (mix well)
if no change add concentrated ammonia

42
Q

Cl ppt

43
Q

Br ppt

44
Q

I ppt

45
Q

which ppt is soluble in dilute ammonia

46
Q

which ppts are soluble in conc and dilute ammonia

47
Q

observation on adding HCl to either CO3 2- or HCO3 -

A

effervescence
colourless gas

48
Q

Na2CO3 + HCl —>

A

NaCl + CO2 + H2O

49
Q

NaHCO3 + HCl —>

A

NaCl + H2O + CO2

Chemistry (39 decks)

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