physical properties Flashcards
what are the states at RTP and appearances of the halogens?
fluorine - gas (yellow gas) chlorine - gas (green gas) bromine - liquid (orange liquid) iodine - solid (grey solid) astatine - solid (black solid)
Describe and explain the trend in atomic radius down the group?
- increase
- more electrons so more shielding
Give the definition, describe and explain the trend in electronegativity down the group?
- the ability of the nucleus of an atom to attract 2 electrons in a covalent bond
- decrease
- larger atoms and more shielding so there is a weaker attraction between the nucleus and electrons
Describe and explain the trend in melting point down the group?
- increases
- larger molecules have more van der Waals forces so a stronger attraction that requires larger amounts of energy to overcome
Give the definition, describe and explain the trend in first ionisation energy down the group?
- the amount of energy required to remove one electron from every atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions
- decreases
- the atoms get larger and there is more shielding so there is a weaker attraction between the nucleus and electrons which means it is easier to remove an electron
Describe and explain the trend in oxidising ability down the group?
- decreases
- as halogens react by gaining an electron and forming a halide ion, they act as oxidising agents. as you go further down the group, the molecules get larger as there is more shielding therefore the attraction between the nucleus and electrons decreases meaning it is harder to gain electrons (be an oxidising agent)
What is the difference between reducing agents and oxidising agents?
- reducing agents lose electrons and are donators
- oxidising agents gain electrons and are acceptors
What is the theory of displacement for halogens and halides?
a more reactive halogen will displace a less reactive halide from the solution (if the halogen is above the halide on the periodic table, the halogen displace the halide)
What displacement reactions will happen with chlorine?
chlorine will displace bromide and iodide
What displacement reactions will happen with bromine?
bromine will displace iodide
What displacement reactions will happen with iodine?
iodine will not react with fluoride, chloride or bromide
What reaction occurs with chlorine water and:
1) KCl
2) KBr
3) KI
1) no reaction
2) an orange aqueous solution - bromine displaced
3) a brown aqueous solution - iodine displaced
What reaction occurs with bromine water and:
1) KCl
2) KBr
3) KI
1) no visible change
2) no reaction
3) a brown aqueous solution - iodine displaced
What reaction occurs with iodine water and:
1) KCl
2) KBr
3) KI
1) no visible change
2) no visible change
3) no reaction
Describe and explain the trend in reducing ability down the group?
- increases
- the size of the ions increases and so does shielding so there is a weaker attraction between the nucleus and electrons. this means the electrons are more easily lost and transferred
What are the products of an acid/halide base reaction?
Observations?
Equation?
- a hydrogen halide (HF, HCl, HBr) and …HSO4
- misty white fumes from the hydrogen halide
e. g., NaCl + H2SO4 –> NaSO4 + HCl
Is an acid/base reaction a redox reaction?
Why is it/is it not?
- no
- the oxidation states of the elements stay the same so nothing is reduced or oxidised
- hydrogen halides are not strong enough reducing agents to reduce the sulfuric acid so the reaction stops
What is the method for identifying halide ions?
1) add dilute nitric acid
2) add silver nitrate solution
3) observe the colour of precipitate formed
4) test the solubility using dilute and concentrated ammonia
What are the results after adding silver nitrate to halides?
F- ions = no reaction
Cl- ions = white precipitate
Br- ions = cream precipitate
I- ions = yellow precipitate
What are the results after adding dilute ammonia to the halides?
F- ions = no reaction
Cl- ions = precipitate dissolves into colourless solution
Br- ions = no visible change
I- ions = no visible change
What are the results after adding concentrated ammonia to the halides?
F- ions = no reaction
Cl- ions = no visible change
Br- ions = precipitate dissolves into colourless solution
I- ions = no visible change
what are the ionic equations for silver nitrates (Ag+) and halide ions (Cl-, Br- and I-)
1) Cl- + Ag+ –> AgCl
2) Br- + Ag+ –> AgBr
3) I- + Ag+ –> AgI
What is the trend in solubility of the silver halides in ammonia?
solubility decreases down the group
what is the test for Sulfur dioxide?
it turns acidified potassium dichromate from organe to green
what is the test for hydrogen sulfide?
turns lead ethanoate from colourless to black
What are the equations and product observations when you add NaF or NaCl to H2SO4?
(1 equation for each)
NaF + H2SO4 –> NaHSO4 + HF
(white fumes)
NaCl + H2SO4 –> NaHSO4 + HCl
(white fumes)
What are the equations and product observations when you add NaBr to H2SO4?
(2 equations)
NaBr + H2SO4 –> NaHSO4 + HBr
(white fumes)
2HBr + H2SO4 –> Br2 + SO2 + 2H2O
(orange fumes) (colourless fumes)
What are the equations and product observations when you add NaI to H2SO4?
(3 equations)
NaI + H2SO4 –> NaHSO4 + HI
(white fumes)
2HI + H2SO4 –> I2 + SO2 + 2H2O
(purple fumes) (colourless fumes)
6HI + SO2 –> H2S + 3I2 + 2H2O
(smelly gas) (purple fumes)
Give an equation for the reaction with solid sodium bromide and concentrated sulphuric acid:
What is the observation?
2NaBr + 2H2SO4 –> Na2SO4 + SO2 + Br2 + 2H2O
solution turns brown/orange
What is the reason for adding dilute nitric acid in the method for identifying halide ions?
dissolves any soluble carbonates
What is the reason for adding ammonia in the method for identifying halide ions?
dissolves the AgBr, AgCl or AgI precipitate
what are the 4 roles of H2SO4?
1) catalyst
2) proton donor (acid)
3) oxidising agent
4) dehydrating agent
