Group 7 Flashcards

1
Q

Colours of 4 main halogens at room temp & pressure

A
  • F - pale yellow (g)
  • Cl - green (g)
  • Br - red/brown (l)
  • I - grey (s)
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2
Q

Describe and explain trends in Boiling Points

A
  • Increses down group
  • incresing strength of Van Der Waals force
  • due to increasing number of electrons
  • more energy needed to break force
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3
Q

Describe and explain trends in Electronegativity

A
  • Decreases down group
  • greater atromic radius as outer electrons are further from nucleus
  • greater nuclear charge and shielding
  • Reduced attraction between electrons and nucleus
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4
Q

Oxidising power trend in group 7

A
  • Less reactive Down group
  • outer electron further from nucleus
  • Less powerful oxidising agent
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5
Q

Describe how halogens act as Oxidising Agents in a displacement reaction

A
  • halogen displaces halide = halide is below halogen in periodic table
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6
Q

Displacement trend of halogens and halides

A
  • Chlorine displaces Br- and I-
  • Bromine displaces I-
  • Iodine has no reaction with F-, Cl-, Br
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7
Q

What is the ionic equation for a displacement reaction Using Chlorine

A

Cl2 (aq) + 2X- (aq) → 2Cl- (aq) + X (aq)

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8
Q

What is the ionic equation for a displacement reaction Using Bromide

A

Br2 (aq) + 2I- (aq) → 2Br- (aq) + I (aq)

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9
Q

Name all halide solutions with their colours

A
  • Potassium Chloride KCl (aq) - colourless
  • Potassium Bromide KBr (aq) - colourless
  • Potassium iodide KI (aq) - colourless
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10
Q

Halide displacement reaction in Chlorine water solution

A

Chlorine water - colourless
* KCl - no reaction
* KBr - orange solution (Br2)
* KI - brown solution (I2)

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11
Q

Halide displacement reaction in Bromine water solution

A

Bromine Water - Orange
* KCl - no reaction
* KBr - no reaction
* KI - brown solution (I2)

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12
Q

Halide displacement reaction in Iodine Solution

A

Iodine Solution - Brown
* KCl - no reaction
* KBr - no reaction
* KI - brown solution (I2)

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13
Q

Name 2 uses of Chlorine

A
  1. Kill bacteria in water
  2. To make bleach
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14
Q

What type of reaction is needed in the uses of chlorine?

A

A dispropotionation reaction

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15
Q

Define Disporoprtionation reaction

A

A redox reaction in which atoms of the same element are both oxidised and reduced

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16
Q

Write the equation of chloring and water

A

Cl2 (g) + H2O (l) → HClO (aq) + HCl (aq)

17
Q

Oxidation state of chlorine in:
* HClO
* HCl

A
  • HClO: +1
  • HCl: -1
18
Q

Ox. state equation of chlorine with water

A

Cl2 (g) + H2O (l) → 2H+ (aq) + Cl- (aq) + ClO- (aq)

19
Q

Oxidation state of Chlorine in Ox. state equation of Chlorine and water

A
  • Cl2 = 0
  • Cl- = -1
  • ClO- = +1
20
Q

Benefits of Chlorine as water treatment

A
  • Kills diseases causing bacteria
  • Prevents water borne diseases (e.g. Cholera)
  • Prevents algae growth which removes bad tatse, bad smell, discolouration
21
Q

Risks of using Chlorine as water treatment

A
  • Chlorine is a toxic gas - irritates respiratory system if breathed in
  • Toxic liquid - chemical burns on skin/eyes
22
Q

Smallest risk of chlorine as water treatment

A
  • Chlorinated hydrocarbons could be produced which are carcinogenic
  • however benefits outweigh this risk
23
Q

Conditions needed to make bleach

A
  • Chlorine gas
  • Cold & Dilute Aqeous Sodium Hydroxide
24
Q

Equation for chlorine and sodium hydroxide

A

Cl2 (g) + 2NaOH (aq) → NaClO (aq) + NaCl (aq) + H2O (l)

25
Q

Oxidation states of Chlorine in:
* NaClO
* NaCl

A
  • NaClO: +1
  • NaCl: -1
26
Q

Reducing Power trend of halides

A
  • Increases down the group
  • easier to lose electrons as attraction gets weaker
  • ions get bigger so electrons further away from nucleus
  • more shileding due to
27
Q

Write the equation for reaction of NaF/NaCl with H2SO4

A
  • NaF (s) + H2SO4 (l) → NaHO4 (s) + HF (g)
  • NaCl (s) + H2SO4 (l) → NaHO4 (s) + HCl (g)
28
Q

Explain why the reaction stops NaF/NaCl with H2SO4

A
  • HF/HCl formed - not strong enough reducing agent to reduce sulfuric acid
  • Not redox reaction - Halide (-1) and sulfur (+6) Ox. states stay same
29
Q

Write the equations of reaction of NaBr with H2SO4

A
  1. NaBr (s) + H2SO4 (l) → NaHSO4 (s) + HBr (g)
  2. 2HBr (g) + H2SO4 (l) → Br2 (g) + SO2 (g) + 2H2O (l)
30
Q

In the second equation of reaction between HBr and H2SO4, what are the Ox. states of:
* Sufur
* Bromide

A
  • Sufur: +6 to +4 (reduction)
  • Bromide: -1 to 0 (Oxidation)
31
Q
A