10 group 7 Flashcards
what are group 7 elements called?
halogens
describe what fluorine looks like
pale yellow gas
describe what chlorine looks like
pale green gas
describe what bromine looks like
orange/brown liquid
describe what iodine looks like
grey solid
what happens to boiling point down group 7? why?
increases due to increased van de waals forces
what is the trend in electronegativity down group 7? why?
decreases due to atomic radius increasing and more shielding
what is the trend in reactivity down group 7?
decreases
do halogens get more or less oxidising when going down group 7?
less oxidising
what is the rule for halide displacement reactions?
if the halide is lower than the halogen in the periodic table, halogen will displace
what does KBr react with? write an equation and the observation
Cl2
Cl2 + 2Br- -> 2Cl- + Br2
orange solution made
what does KI react with?
Cl2 and Br2
write the equation and state the observation of the reaction of KBr with Cl2
Cl2 + 2Br- -> 2Cl- + Br2
orange solution made
write the equation and state the observation of the reaction of KI with Br2
Br2 + 2I- -> 2Br- + I2
brown solution
what is the chemical name for bleach?
sodium chlorate
NaClO
write the equation for bleach
2NaOH + Cl2 -> NaClO + NaCl + 2H2O
what type of reaction is the one for bleach?
disproportionation reaction
what is a disproportionation reaction?
a reaction where an element is both oxidised and reduced
what is reduced and oxidised in the reaction for bleach?
Na
how can you kill bacteria in water?
by adding chlorine gas
what is the equation for the reaction between water and chlorine?
H2O + Cl2 -> 2H+ + Cl- + ClO-
what kind of reaction is the reaction used to kill bacteria in water?
disproportionation reaction
what is both reduced and oxidised in the reaction for killing bacteria in water?
Cl
what are the disadvantages for putting chlorine in drinking water?
- toxic (irritates respiratory system)
- liquid chlorine causes chemical burns
what are the advantages for putting chlorine in drinking water?
- destroys microorganisms that cause disease
- long lasting so reduces bacteria build up
- reduces growth of algae
which, out of I- and F-, is a more powerful reducing agent? why?
I- more powerful because it is at the bottom of group 7 and has a larger atomic radius so the outer electron can be lost more easily
what are two tests that can be used to prove the trend in reducing agents down group 7?
- reaction with sulfuric acid
- reaction with silver nitrate
write the equations for how sodium Cl, Br, I and F all react with sulfuric acid
- H2SO4 + NaCl -> NaHSO4 + HCl
- H2SO4 + NaBr -> NaHSO4 + HBr
- H2SO4 + NaI -> NaHSO4 + HI
- H2SO4 + NaF -> NaHSO4 + HF
what reacts with H2SO4 to make SO2?
Br and I
what reacts with H2SO4 to make S?
I
hat reacts with H2SO4 to make H2S?
I
write the equation for the reaction between H2SO4 and Br to make SO2 and state the observation
H2SO4 + 2H+ + 2Br- -> Br2 + SO2 + 2H2O
brown fumes of Br2
write the equation for the reaction between H2SO4 and I to make SO2 and state the observation
H2SO4 + 2H+ + 2I- -> I2 + SO2 + 2H2O
acidic gas and black solid iodine
write the equation for the reaction between H2SO4 and I to make S and state the observation
H2SO4 +6H+ + 6I- -> 3I2 + S + 4H2O
yellow solid of sulfur
write the equation for the reaction between H2SO4 and I to make H2S and state the observation
H2SO4 + 8H+ + 8I- -> 4I2 + H2S + 4H2O
rotten egg smell and black solid iodine
write the equation for silver ions reaction with F-
give state symbols and state observation
Ag+ (aq) + F- (aq) -> AgF (aq)
colourless solution
write the equation for silver ions reaction with Cl-
give state symbols and state observation
Ag+ (aq) + Cl- (aq) -> AgCl (s)
white precipitate
write the equation for silver ions reaction with Br-
give state symbols and state observation
Ag + (aq) + Br- (aq) -> AgBr (s)
cream precipitate
write the equation for silver ions reaction with I-
give state symbols and state observation
Ag + (aq) + I- (aq) -> AgI (s)
yellow precipitate
what does Br2 look like?
brown fumes
what does S look like?
yellow solid
what is the observation for H2S?
rotten egg smell
what do AgF, AgCl, AgBr and AgI look like?
AgF = colourless solution
AgCl = white precipitate
AgBr = cream precipitate
AgI = yellow precipitate
what is the formula for sulfates and how do you test for them? what observation is a positive result?
SO4 2-
add HCl then BaCl2
white ppt
what is the formula for hydroxides and how do you test for them? what observation is a positive result?
OH-
red litmus/universal indicator
litmus: blue
indicator: blue/purple
what is the formula for carbonates and how do you test for them? what observation is a positive result?
CO3 2-
add HCl
effervesence with CO2
(limewater turns cloudy)
what is the formula for ammonium and how do you test for them? what observation gives a positive result?
NH4+
add NaOH and put damp red litmus over
ammonia gas will turn litmus blue
how do you test for group 2 ions and what are the observations for Ca2+, Sr2+ and Ba2+?
flame tests
Ca2+ = brick red
Sr2+ = red
Ba2+ = pale green
