GROUP 7 Flashcards
What is the appearance and reactivity of fluorine?
very pale yellow gas.It is highly reactive
What is the appearance and reactivity of chlorine
Greenish ,reactive gas, poisonous in high concentration.
State the trends in melting point and boiling point down G7:
Increases down the group.
As the molecules become larger they have more electrons and so have larger van der waals forces so more energy required to break forces.Also down a group physical state changes from gas ,liquid to solid.
State the trends in electronegativity down G7:
Electronegativity decreases.
The atomic radius increases and the outer electrons are further from the nucleus as the shielding increases.The nucleus is therefore
less able to attract the bonding pair of electrons.
What is a displacement reaction?
A more reactive halogen will displace the halide ion of a less reactive halogen from solution.
What colour is a solution that contains chlorine?
Very pale green solution (often colourless)
What colour is a solution that contains bromine?
Yellow/orange solution
what colour is a solution that contains iodine?
brown solution
what is the equation for chlorine displacing bromide ions and state the colour change that occurs?
cl2(aq)+2Br-(aq) →2Cl-(aq)+Br2
colour change= pale green to orange/yellow
What is the equations when chlorine displaces iodine ions and state the colour change?
Cl2(aq)+2I-(aq) →2Cl(aq)+I2
colour change=pale green to brown
what is the equation for bromine displacing iodine ions and state the colour change?
Br2(aq)+2I-(aq)→2Br(aq)+I2(aq)
Colour change=yellow /orange to brown
What is the trend in oxidising power down group 7?
Halogens are good oxidising agents (electron acceptors)
-oxidising power decreases down the groups as their ability to attract electrons decreases down the group.
How do you test for halide ions ?
*spec:Explain why the silver nitrate solution is acidified
1- add dilute nitric acid to remove any soluble impurities that could interfere with the test(e.g. carbonates and hydroxides)
2-add silver nitrate solution to form a silver halide precipitate.
Ag+ (aq) + X– (aq) → AgX (s)
what colour precipitate does AgCl form?
chlorides produce white precipitate
Ag+(aq) + Cl-(aq) → AgCl(s)
What colour precipitate does AgF produce?
Fluorides produce no precipitate
What colour precipitate does AgBr produce?
Bromides produces a cream precipitate
Ag+(aq)+Br-(aq) → AgBr(s)
What colour precipitate does AgI produce)
iodine produces a pale yellow precipitate
Ag+(aq)+I-(aq) → AgI(s)
As AgCl and silver AgBr are similar colours how do we differentiate between them?
You add dilute ammonia and if AgCl is present it will dissolve to give a colourless solution but if AgBr is present it does not dissolve.
As AgBr and AgI are similar colours how do we differentiate between them?
You add concentrated ammonia and if AgBr is present it will dissolve to give a colourless solution but if AgI is present it will not dissolve.
What is the trend in halide ions as reducing agents?
Halide ions are good reducing agents (donates electrons).
-Reducing power increases down the group as its easier to loose electrons from larger ions due to shielding and a large atomic radius.
The reaction between chloride and concentrated sulfuric acid:
- what do you observe?
- what is the equation?
- what is the type of reaction?
NaCl(s)+H2SO4(l)→NaHSO4(s)+HCl(g)
- this is acid base reaction not a redox reaction as chloride ions are poor reducing agents and oxidation states remain unchanged
- white misty fumes of HCl are formed
The reaction between fluoride and concentrated sulfuric acid:
- what do you observe?
- what is the equation?
- what is the type of reaction?
NaF(s)+H2SO4(l)→NaHSO4(s)+HF
(g)
*this is acid base reaction not a redox reaction as fluoride ions are poor reducing agents and oxidation states remain unchanged
*white misty fumes of HF are formed
The reaction between bromide and concentrated sulfuric acid:
- what do we observe?
- what is the equation?
- what is the type of reaction?
1- In the first step we have a acid base reaction
NaBr(s)+H2SO(l)→NaHSO4(s)+HBr(g)
*white steamy fumes of HBr are evolved
2-Bromide ions are stronger reducing agents than chloride so they reduce sulfuric acid into sulfur dioxide in a redox reaction
ox= 2Br- → Br2+2e-
red=H2SO4+2e- + 2H+→SO2+H20
redox=2HBr(aq)+H2SO4(l)→Br2(g)+SO2(g)+2H2O(l)
* orange fumes and sulfur dioxide(a colouless chocking gas) are formed
The reaction between iodide and concentrated sulfuric acid:
- what do we observe?
- what is the equation?
- what is the type of reaction?
1- in the first step we have a acid base reaction
NaI(s)+H2SO4(l)→NaHSO4(s)+HI(g)
*White steamy fumes of Hi are evolved
2-iodine ions are the strongest halide reducing agents so it reduces the sulfuric acid into sulfur,sulfur dioxide, hydrogen sulfide:
ox=2I-→I2+2e- (same for all 3)
redox=2HI (aq) + H2SO4 (l) → I2 (g) + SO2 (g) + 2H2O (g)
*so2 forms a colourless acidic chocking gas & black solid
redox= 6HI (g) + H2SO4 (g) → 3I2 (s) + S (s) + 4H2O (l)
*s forms a yellow solid&black solid
redox=8HI (aq) + H2SO4 (l) → 4I2 (s) + H2S (g) + 4H2O (l)
*a colourless gas which smells of bad egg &black solid