INORGANIC CHEM - GROUP 7 Flashcards
How many electrons do group 7 elements gain when they react?
1
What is the charge of group 7 ions?
1-
How does atomic radius change down the group?
- increases
- more shells
State the trend in melting and boiling points down group 7
increase down the group
Explain the trend in melting and boiling points down group 7
- increase in atomic radius
- increased strength of VDW forces
- more energy required to overcome VDW forces
State the trend in electronegativity down group 7
decreases down the group
Explain the trend in electronegativity down group 7
- atoms get larger (more shells)
- more shielding
- electrons are further away from the nucleus which means that there are weaker forces of attraction between nucleus and electrons so its harder for the group 7 atom to attract electrons to itself
State the trend in 1st ionisation energy down group 7
decreases down the group
Explain the trend in 1st ionisation energy down group 7
- increase in atomic radius
- increase in shielding
- electrons more easily lost
What colour and state is fluorine?
a pale yellow gas
What colour and state is chlorine?
a green gas
What colour and state is bromine?
a red-brown liquid
What colour and state is iodine?
a grey-black solid
What colour is iodine in gaseous form?
purple
State the trend in reactivity down group 7
decreases down the group
Explain the trend in reactivity down group 7
- atoms get larger (more shells)
- more shielding
- electrons are further away from the nucleus which means that there are weaker forces of attraction between nucleus and electrons so its harder to gain an electron, the harder it is to gain an electron, the less reactive the element
A _____ reactive halogen will replace a ____ reactive halide ion in a displacement reaction
A more reactive halogen will replace a less reactive halide ion in a displacement reaction
Order Cl, Br and I in terms of oxidising power from strongest oxidising agent to weakest oxidising agent and explain
- strongest: Cl
- Br
- weakest: I
- Explanation: halogen atoms gain electrons when they oxidise halide ions. the smaller the halogen atom, the easier it is to gain an electron as it is smaller and has less shielding
For all halide ions that Cl would displace, give the equation and observation
- Br^- :
Cl2 + 2Br^- -> 2Cl^- + Br2
observation: yellow solution forms - I^-:
Cl2 + 2I^- -> 2Cl^- + I2
observation: brown solution forms
For all halide ions that Br would displace, give the equation and observation
- I^-:
Br2 + 2I^- -> 2Br^- + I2
observation: brown solution forms
For all halide ions that I would displace, give the equation and observation
no reaction with F^-, Cl^- or Br^-
Give the observation, equation and type of reaction for the reaction between Cl^- and H2SO4 to form HCl
- observation: white misty fumes
- equation: NaCl + H2SO4 -> NaHSO4 + HCl
- type of reaction: acid-base
Give the observation, equation and type of reaction for the reaction between Br^- and H2SO4 to form HBr
- observation: white misty fumes
- equation: NaBr + H2SO4 -> NaHSO4 + HBr
- type of reaction: acid-base
Give the observation, equation and type of reaction for the reaction between Br^- and H2SO4 to form Br2
- observation: brown vapour
- equation: 2HBr + H2SO4 -> Br2 + SO2 + 2H2O
- type of reaction: redox (Br is oxidised, S is reduced)
Give the observation, equation and type of reaction for the reaction between I^- and H2SO4 to form HI
- observation: white misty fumes
- equation: NaI + H2SO4 -> NaHSO4 + HI
- type of reaction: acid-base
Give the observation, equation and type of reaction for the reaction between I^- and H2SO4 to form I2
- observation: purple vapour
- equation: 2HI + H2SO4 -> I2 + SO2 + 2H2O
- type of reaction: redox (I is oxidised, S is reduced)
Give the observation, equation and type of reaction for the reaction between I^- and H2SO4 to form S
- observation: yellow solid
- equation: 6HI + H2SO4 -> 3I2 + S + 4H2O
- type of reaction: redox (I is oxidised, S is reduced)
Give the observation, equation and type of reaction for the reaction between I^- and H2SO4 to form H2S
- observation: gas smells of rotten eggs
- equation: 8HI + H2SO4 -> 4I2 + H2S + 4H2O
- type of reaction: redox (I is oxidised, S is reduced)
Order Cl^-, Br^- and I^- in terms of reducing power from strongest reducing agent to weakest reducing agent and explain
- strongest: I^-
- Br^-
- weakest: Cl^-
- Explanation: halide ions lose an electron when they reduce H2SO4 ions. the bigger the halide ion, the easier it is to lose an electron
What is Cl used for?
- used to sterilise water - when you mix Cl with water it undergoes disproportionation. a mixture of Cl^- (chloride) ions and ClO^- (chlorate) ions. ClO^- ions kill microorganisms/bacteria
- Cl2 + 2NaOH -> NaClO + NaCl + H2O - sodium chlorate (NaClO) is sold commercially as bleach
