GROUP 7 Flashcards
What is the trend in the boiling point down group 7? why? (4)
Increases down the group
size of atoms increases
increase in number of electron so
stronger van der waals forces of attraction between molecules require more energy to overcome
What is the trend in electronegativity down group 7? Why? (5)
Decreases
increased atomic radius
more shielding
outer e- further away from nucleus
more difficult yo attract electron density in a covalent bond
state and explain trend in oxidising ability in group 7
going down G7 halogens become weaker oxidising agents.
Larger radius
Weaker attraction between nucleus and outer e-
Describe what you would see if you combined the following reagents and write stoichiometric and ionic equations for any reactions that take place
- Br2 (aq) with NaF (aq)
- Cl2 (aq) with NaBr (aq)
- Br2 (aq) with NaI (aq)
- No reaction occurs, Bromine can’t displace fluoride
- An orange- brown solution forms
Cl2(aq) + 2NaBr(aq) –> 2NaCl(aq) + Br2(aq)
Cl2(aq) + 2Br-(aq) –> 2Cl-(aq) + Br2(aq)
- Orange solution turns brown
Br2(aq) + 2NaI(aq) –> 2NaBr(aq) + I2(aq)
Br2(aq) + 2I-(aq) –> 2Br-(aq) +I2(aq)
State and explain the trend in reducing ability of the halide ions
Reducing strength increases down group
ions radius increases
Weaker attraction between outer e- and nucleus
Identify 2 solid sodium halides that can’t reduce concentrated sulphuric acid. write simplest ionic equations for a reaction occurring with just on for a reaction occurring with just one of theses halides and give oberservations
H+ + F- –> HF
Ob: misty fumes of HF gas
H+ + Cl- –> HCl
Ob: misty fumes of HCl gas
state the observation you would make if either of NaCl or NaF was reacted with concentrated sulphuric acids
steamy white fumes
Name the products formed when solid NaBr reacts with concentrated H2SO4 and state the observations you would make upon their function
Steamy fumes of HBr
brown fumes of Br2
colourless fum of SO2 gas
colourless solution of NAHSO4
Write redox equations for the formation of Br with H2SO4
2Br –> Br2 + 2e-
H2O4 + SH+ + 2e- –> SO2 + 2H2O
H2SO4 + 2H+ + 2Br- —> SO2 + 2H2O + Br2
Give a common use of Sodium hypochlorite (NaClO)
used as disinfectant as it kills bacteria
Write and equation for the reaction between Chlorine and cold dilute sodium hydroxide
Cl2(g) + 2NaOh(aq) —-> NaCl(aq) + NaClO(aq) + H2O(l)
Even though chlorine is toxic , why do we add it to swimming pools? (2)
adding chlorine to swimming pools kills bacteria.
health benefits of adding very small amount if Cl to water outweigh the risks
write equation for the reaction between H2O and Cl in the presence of direct sunlight
2Cl2(g)+ 2H2O (l) (EQUALIBRIUM SIGN) 4HCl (aq) + O2(g)
What does disproportination reaction mean?
reaction in which one reactant species is simultaneously oxidised and reduced
write the equation for the reaction between water and chlorine to form 2 chlorine- containing products
Cl2(g) + H2O(l) (EQUILIBRIUM ARROW) HCL(aq) + HCLO(aq)
test for carbonate ions
Add H2SO4
effeservence
Co2 produced
<write a half equation for the formation of Iodine from Iodide ions
2I- —-> I2 + 2e-
Test for hydroxide ions
MgCl2
White ppt
Mg(OH)2 formed
Test for ammonium ions
add NaOH
warm it
gas turns dam red litmus paper blue it indicates ammonium ions were present
ionic equation for NaBr and silver nitrate
Ag+ (aq) + Br-(aq) —-> AgBr(s)
why is the silver nitrate test used to identify used to identify halide ions
produces precipitate that are easily identified by colour
Fluoride reaction with ammonia
colour of precipitate
No reaction
no colour
Chloride reaction with ammonia
colour of precipitate
colour: white ppt
reaction: Dissolve in dilute ammonia
Bromide reaction with ammonia
colour of precipitate
colour: Cream ppt
reaction: Dissolve in concentrated ammonia
Iodide reaction with ammonia
colour of precipitate
colour: yellow ppt
reaction: insoluble in concentrated ammonia
why is dilute nitric acid added before the silver nitrate for a halide test
to remove soluble carbonate and hydroxide ions would give a false +ve result
describe how you would carry out the halide test
- Dissolve sample in water
- Add HNO3
- Add AgNO3 solution
- Change in colour
- Add dilute NH3
- Add conventrayed NH3
write half equations for the formation of the 3 sulfur-contacting reduction products of this reaction
H2SO4 + 2H+ + 2e- –> SO2 + 2H2O
H2SO4 + 6H+ + 6e- —> S + 4H2O
H2SO4 + 8H+ + 8I- —> H2S + 4H2O
write a redox equations for the formation of the 3 sulphur- containing reductions products of this reaction
H2SO4 + 2H+ + 2I- —> SO2 + 2H2O + I2
H2SO4 + 6H+ + 6I- —-> S + 4H2O + 3I2
H2SO4 + 8H+ + 8I- —> H2S + 4H2O + 4I2
Name the products formed when solid NaI reacts with concentrated sulphuric acid and state the observations you would make upon their formation
steamy fumes of HI
black solid of I2
Bad eggs smell caused by H2S
yellow solid of S
colourless solution of NaHSO4
Write equation for the precipitates
Ag+ + I- ——> AgI
Ag+ + Br- ——> AgBr
Ag+ + Cl- ——> AgCl
Equation for NH3 with
AgCl
AgBr
AgCl + 2NH3 ——> Ag(NH3)2 +Cl-
AgBr + 2NH3 ——> Ag(NH3)2 +Br-
Cl is often added to water because it….
Sterelises wate4 by killing bacteria
