Group 7: Halogens Flashcards
What is the trend in electronegativity down group 7?
DECREASES
bc the number of principle energy levels (shells) increases
weaker attraction to nucleus and electrons in a covalent bond
What is the trend in boiling point down group 7?
INCREASES
size of atom increases
there are more VDW forces between molecules that need to be broken
What do Halogens look like at room temperature?
F2 - pale yellow gas
Cl2 - pale green gas
Br2 - Dark red/orange liquid
I2 - dark purple/black solid
What happens to a halogen’s ability to act as an oxidising agent down a group?
DECREASES
- atomic radius increases
- more shielding
- weaker attraction to nucleus and outer electrons so halogen gains electron less easily
What is the observation when chlorine oxides Br- and I-
Br- = yellow solution is formed
I- = brown solution formed
What is the observation when Br oxidises I-?
brown solution formed
What is the ionic equation for the oxidation of Br- by Cl2
Cl2 + 2Br- > Br2 + 2Cl-
What is the ionic ewuation for the oxidation of I- by Cl2?
Cl2 + 2I- > I2 + 2Cl-
What is the ionic equation for the oxidation of I- by Br2
Br2 + 2I- > I2 + 2Br-
What happened to the ability of a Halogen to act as a reducing agent down a group?
INCREASES
- size of halogen increases
- outer electron is further from nucleus
- less attraction between nucleus ant outer electron so they lose an electron easily
How can you test the reducing ability of Halide ions?
an acid base reaction
by reacting solid halide salts with concentrated sulphuric acid
What is the equation for a halide salt with sulphuric acid?
NaX + H2SO4 > NaHSO4 + HX
What is the observation for HX
misty fumes
What reaction does F- (NaF) undergo?
not a strong reducing agent so only does an acid base reaction
NaF + H2SO4 > NaH2SO4 + HF
misty fumes
What reaction does Cl- (NaCl) undergo?
only undergo acid base reaction
stronger than fluorine but still not strong enough to reduce the sulphuric acid
NaCl + H2SO4 > NaH2SO4 + HCL
misty fumes
What reactions do Br- (NaBr) undergo?
Both acid base reaction and redox
stronger reducing agents than Cl ions
It reduces H2SO4 to SO2
What observations come from Br- redox reaction?
Choking gas - SO2
Brown gas - Br2
What is the equation for Br- redox reaction?
2e- + 2H+ + H2SO4 > SO2 + 2H2O
2Br- > Br2 + 2e-
2H+ + H2SO4 + 2Br > Br2 + SO2 + 2H2O
What reactions does I- (NaI) undergo?
Acid base reaction
and 3 redox rection
reduces H2SO4 to, H2S, SO2 and S
What are the observations in each redox reaction with I-
SO2 - choking gas
H2S - rotten egg smell
S - yellow solid
I2 - black solid and purple gas
How can you identify Halides in a solution?
using acidified silver nitrate
What is the full and ionic equation for a Halide with silver nitrate?
full
AgNO3 + NaX > AgX + NaNO3
ionic
Ag+(aq) + X-(aq) > AgX
What are the observations with Halide ions and silver nitrate?
AgF = NVC insoluble
AgCl = white ppt
AgBr = cream ppt
AgI = yellow ppt
Why should Hydroxide and carbonate ions be removed before testing with Ag?
they both form a ppt in Ag and will interfere with the reaction
What is the equation for removing carbonate ions using nitric acid?
2HNO3 + Na2CO3 > 2NaNO3 + CO2 + H2O
ionic
2H+ + CO3(^2-) + H2O + CO2
What is the trend in solubility in DILUTE NH3 down group 7?
decreases from AgCl to AgI
AgI is insoluble
What is the equation for AgCl in dilute NH3?
AgCl(s) + 2NH3(aq) > Ag(NH3)2+(aq) + Cl-
What is the trend in solubility in CONCENTRATED NH3?
AgBr is soluble
AgI is insoluble
What is the equation for AgBr in concentrated NH3
AgBr(s) + 2NH3(aq) > Ag(NH3)2+(aq) + Br-(aq)
What is the equation for chlorine dissolving in water?
Cl2(g) + H2O ⇆ HCl(aq) + HClO(aq)
What id a disproportionatiom reaction?
when an atom goes through is both oxidised AND reduced
What happened when universal indicator paper is added to chlorine water?
turns red first - both reaction products are acids
then it turns white as HClO is an effective bleach
What happenes when chlorine is bubbled in water in prescense of sunlight?
a colourless gas is produced and the green colour due to chlorine fades
chlorine oxidises water to O2,and chlorine is reduced to chloride
What is the equation for Cl and H2O in sunlight?
2Cl2 + 2H2O > 4HCl + O2
What is the use of chlorine in water treatment?
sterilises water for swimming pools
kills bacteria
What is the equation for the reaction with Chlorine and cold dilute sodium hydroxide?
Cl2 + 2NaOH > H2O + NaCl + NaClO
What is the use of NaClO?
active ingredient in house bleach
