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Chemistry - Target Mechanics > Halogens > Flashcards

Halogens Flashcards

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1
Q

How does fluorine exists naturally? - state and colour

A

A pale yellow gas

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2
Q

How does chlorine exist naturally - colour and state

A

Pale green gas

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3
Q

How does bromine exist naturally - state and colour

A

(Brown) Orange liquid

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4
Q

How does iodine exist naturally - state and colour

A

Grey solid

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5
Q

Colour of AgCl precipitate

A

white

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6
Q

Colour of AgBr precipitate

A

cream

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7
Q

Colour of AgI precipitate

A

Yellow

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8
Q

Which of the silver halide precipitates dissolve in dilute ammonia

A

AgCl ONLY

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9
Q

Which of the silver halide precipitates dissolves in excess ammonia

A

AgCl
AgBr

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10
Q

Which of the silver halide precipitate doesn’t dissolve in ammonia

A

AgI

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11
Q

What is the trend in reducing power down the halogens

A

-increase in reducing power
-as they’re oxidised (lose e-) more easily down the group —> ionisation energies increase down group due to increase shielding outweighing increase in nuclear charge

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12
Q

How does reactivity change down the halogen group?

A
  • Decreases
    -Halogens want to gain 1e- to have stable noble gas configuration
    -down group atomic radius and shielding increases, outweighing increase in nuclear charge
    -so electrons are attracted less strongly
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13
Q

How does oxidising power change down the group?

A
  • Decreases
  • halogens are reduced (gain electron) less easily due to increase in atomic radius, shielding which outweigh increase in nuclear charge
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14
Q

How do we measure a halogens reducing power?

A

-By reacting halide salt with concentrated sulfuric acid and observing whether a further reaction occurs

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15
Q

Describe the describe between KCl and conc H2SO4, give the reaction and state conclusions we make

A

KCl (s) + H2SO4 (aq) —> KHSO4(s) + Hcl (g)

White steamy fumes of HCl observed

No further reaction occurs , HCl doesn’t react further with H2SO4

Acid-base NOT redox reaction, so Cl must not be a very good reducing agent

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16
Q

Describe the reaction between KBr and H2SO4, state any further reactions and observations

A
  1. KBr + H2SO4 —> KHSO4 + HBr
    (HBr reacts further—> better reducing agent that chlorine)
  2. 2HBr + H2SO4 —> SO2 + Br2 + 2H2O
    (REDOX reaction —> bromine oxidised and sulfur is reduced )

Firstly white steamy fumes are given off

Then in the second reaction the solution will either turn orange (due to bromine), or you’ll see red/orange fumes or bromine gas

17
Q

Describe the reaction between KI and H2SO4, state any further reactions and observations

A
  1. KI + H2SO4 —> KHSO4 + HI Acid/base
    (HI reacts further with H2SO4–> good reusing agent )
  2. 8HI + H2SO4 —> H2S + 4I2(s) + 4H2O
    (REDOX)

Observations :
1.White steamy fumes of HI given off
2 . Black solid of iodine form, or purple iodine gas is seen, H2S has a bad egg smell

18
Q

Give quantitative evidence for the difference in reducing strengths of the halogens

A

• Chlorine is unable to change the oxidation state of sulfur in H2SO4

•Bromine is able to reduce sulfur to the extent that it’s oxidation state goes from +6 in H2SO4 to +4 in SO2

•Iodine is able to reduce sulfur to the extent that it’s oxidation state goes from +6 in H2SO4 to -2 H2S (LARGE CHANGE)

Therefore reducing power increases down group, and out of Cl Br and I, iodine is best reducing agent

19
Q

How do we test for the difference in oxidising strength of the halogens?

A

-By adding a halide salt to a solution of liquid halogen
-more reactive halogens (the better oxidising agents), displace the halide in the salt, causing a colour change

20
Q

Why do we add an organic solvent - such as hexane- to the solution of the halide salt and halogen

A
  • It allows us to see the colour change more clearly, as halogens are non-polar, so dissolve better in organic solvents and can be seen more clearly
21
Q

State the colours of iodine, chlorine and bromine in an organic solvent

A

Chlorine - pale Green

Bromine - orange

Iodine - purple

22
Q

Why are solvents important it comes to halogens?

A
  • Halogens appear different colours in different solvents
23
Q

State the colours of chlorine iodine and bromine in an aqueous solvent

A

Chlorine - colourless

Bromine - yellow

Iodine - brown

24
Q

What is the important thing to remember about halogen displacement reactions?

A

-Halogens displace all Halogens BENEATH them in the group
- as reactivity decreases down group, so most reactive halogens are at the top (best oxidising agents at the top)

25
Q

Write the equation for the reaction between chlorine and cold dilute NaOH

A

2NaOH + Cl2 —> NaCl + NaClO + H2O

-This process is used industrially to produce bleach - NaClO

26
Q

Write the equation for the reaction between chlorine and hot concentrated NaOH

A

6NaOH + 3Cl2 —> 5NaCl + NaClO3 + 3H2O

27
Q

Give the full equation for the reaction between KCl and H2SO4, and state the reaction type

A

KCl + H2SO4 —> HCl + KHSO4

-acid base reaction

28
Q

Give the full equation for the reaction between KBr and H2SO4, and state the reaction type

A

2NaBr + 3 H2SO4 —> NaHSO4 + SO2 + Br2 + 2H2O

-Redox reaction
-Orange fumes of Br2 given off

Chemistry - Target Mechanics (21 decks)

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