Chapter 10 - Group 7 Flashcards
why are halogens diatomic
because when they are monoatomic, they are highly unstable because they have one unpaired electron
why are halide ionicc compounds more stable than halogens
because in ionic compounds the halogen has an electron to fill up its outer shell and make it fully stable, while in a halogen, the halide has to share its electron
whats the difference between halide and halogen
halide is an ion, all halides have charge of -1
halogen is the name for the diatomic molecule that all g7 elements form
why are halogens reactive
they have only one electron that they need to gain to obtain a full outer shell, so it is much easier for them to become compounds
what is the trend in reactivity down group 7 and why
reactivity decreases down the group because the shielding increases so the atomic radius increases so the outermost shell is further from the nucleus so it experiences a weaker attraction so for the element to gain an electron on a further shell it requires more energy
what is the trend in electronegativity down group 7 and why
decreases because the shielding increases so atomic radius increases so shared electrons are further from the nucleus so they experience a smaller attraction to the nucleus and are pulled less towards it
what is th emost electronegative elemtn
fluorine
how does boiling point (and melting point) change down group 7 and why
increases because the sheulding increases so number of eletcons increases so greater surface area so greater van der waals forces
what intermolecular forces do halogens experience
only van der waals forces because they are non-polar molecuoles with no ability to form hydrogen bonds
what does F2 look like
it is a pale yellow gas
what does Cl2 look like
pale green gas
what does Br2 look like
Oorange/brown liquid
what does I2 look like
black / purple solid
how does oxising power of halogens change down the group
it decreases
how does reducing power of halides change down the group
it increases
why are chloride ions bad reducing agents
because thier atomic radius is so small that they struggle to lose electrons since they experience so much attraction to the nucleus
give a general equation for the reaction of a halogen salt with sulfuric acid
what are the observation foir tyhis reaction
NaX + H2SO4 —-> HX + NaHSO4
streamy fumes forming
give the equation between hydrogen vbromide and sulfuric acid
what rre the observations
2H+ + 2Br- + H2SO4 —-> SO2 + 2H2O + Br2
colourless choking gas and brown fumes
what is reduced and what is oxidised, and to what, in the reaction between hydrogen bromide and sulfuric acid
brinmide ions are reduced to bromine
sulfuric acid is reduced to sulfur dioxide
how can you tell that iodide ions are the strongest reducing agesnt
sulfur gets reduced from its oxidation state of +6 ibn sulfuric aduic to an oxidation state of -2 in hjydrogen sulfide
Give the reaction that takes place between chlorine and water in bright sunlight.
2Cl2 + 2H2O —->
Why is
HClO
more useful than
HCl
for sterilising pools?
The bacteria in the water are killed by oxidation using
HClO
Why do outdoor pools require more chlorine to sterilise them than indoor pools?
In the presence of sunlight, chlorine reacts with water to form hydrochloric acid and oxygen, in an irreversible reaction. In outdoor pools, there is brighter sunlight, so this reaction happens more rapidly. This causes chlorine to be lost from the pool, meaning less chlorine is available to react with water to form chloric (I) acid, which is the oxidising agent needed to kill bacteria. Therefore outdoor pools require more chlorine to sterilise them than indoor pools.
in what conditions will chlorine react with sodium hydroxide to give sodium chlorate (I)
it must react with cold and dilute sodium hydroxide
give the equation for the reaction between sodium hydroxide and chlorine to give sodium chlorate
Cl2(aq) + 2NaOH(aq) —> NaClO(aq) + NaCl(aq) + H2O(l)
