Flashcards
Group 7
Flashcards do conjunto (33)
- 1Colours of: -fluorine -chlorine -bromine -iodineFluorine is a pale yellow, chlorine is a greenish gas, bromine a red-brown liquid, and iodine a black solid
- 2How their appearance changes going down the group?-Get darker and denser going down the group
- 3Why are the properties of fluorine untypical?The F-F bond is unexpectedly weak, compared with the trend for the rest of the halogens. The small size of the fluorine atom leads to repulsion between non-bonding electrons because they are so close together.
- 4Trend in electronegativity down a groupDecreases going down a group as there are more electron shells and more shielding so there is less of an attraction from the positive nucleus to attract electrons and so electronegativity decreases.
- 5Trends in the melting and boiling pointsincrease going down the group as larger atoms mean more electrons and so van der waals forces are stronger. The lower the boiling point, the more volatile the element.
- 6Are halogens oxidising or reducing agents?oxidising agents- they get reduced during redox reactions
- 7How the oxidising ability changes going up/ down the groupOxidising ability increases going up the group
- 8What is a displacement reaction?When a more reactive halogen will displace a less reactive halogen
- 9What are spectator ions?Ions that are not involved in the redox reaction
- 10How do you extract bromine from sea water?Sea water contains bromide ions which can be oxidised to bromine by chlorine
- 11How does reactivity of a halogen change down a group?less reactive going down the group, atoms get larger and outer shell is further away from the nucleus , so electrons are less strongly attracted to it.
- 12How is bleach made up? What type or reaction is this?Chlorine and sodium hydroxide...
The oxidation state of chlorine goes up and down- is a disproportionation reaction - 13Uses of bleach?-Water treatment
-bleach paper and textiles
- cleaning toilets - 14How does chlorine kill bacteria when added to water?When mixed with water, chloring undergoes disproportionation, you end up with chloride ions and chlorate ions. Chlorate ions kill bacteria.
- 15Two advantages of treating water with chlorine?- Kills disease causing bacteria
-Prevents growth of algae, eliminating bad tastes and smells - 16Risks of using chlorine in water treatment?-Harmful if breathed in and irritates the respiratory system
-Liquid chlorine on skin can cause serious burns
- chlorine reacts with a variety of organic compounds within the water to form chlorinated hydrocarbons which can be cancer causing. - 17Trends in halides acting as reducing agents?Increases reducing ability going down the group as electrons are further from the nucleus and there is more shielding so electrons are more easily lost.
- 18Equation of sulfuric acid?H2SO4
- 19Reaction of sodium chloride with sulfuric acid? Observations? Why is this not a redox reaction?Steamy fumes of hydrogen chloride are seen. The solid product is sodium hydrogensulfate.
Reaction is NaCl (s) + H2SO4 (l) ----- NaHSO4 (s) + HCl(g)
- No oxidation state has been changed. The chloride ion is too weak a reducing agent to reduce the sulfur in sulfuric acid. - 20Observations of sodium bromide with sulfuric acid?- see many fumes of hydrogen bromide and brown fumes of bromine. Colourless sulfur dioxide is also formed.
- 21Two reactions that take place? What type of reaction is this and is it an endothermic or exothermic reaction?1- First, sodium hydrogensulfate and hydrogen bromine are produced.
NaBr + H2SO4 ---- NaHSO4 +HBr
Bromide ions are a strong enough reducing agent to reduce the sulfuric acid to sulfur dioxide.
2H+ + 2Br- + H2SO4 ---- SO2 + 2H2O +Br2
-redox reaction
-exothermic - 22Observations of Reaction of sodium iodide with sulfuric acid.- See fumes of hydrogen iodide, the black solid of iodine and bad egg smell of hydrogen sulfide gas is present, yellow solid sulfur may also be seen- colourless sulfur dioxide is also formed.
- 23The different reactions that take place between sodium iodide and sulfuric acid?1-hydrogen iodide and sodiu,m hydrogen sulfate is produced as before
2-Iodine ions are better reducing agents than bromide so they reduce the sulfur in sulfuric acid even further, so that sulfur dioxide, sulfur, and hydrogen sulfide gases are produced. - 24How are all metal halides (except fluorides) identified?By reacting them with silver ions
- 25Why is silver fluoride an exception?It is soluble and so does not form a precipitate
- 26Why is dilute nitric acid added first?To get rid of any soluble carbonate ( CO32-)or hydroxide (OH-) impurities. These would interfere with the process by forming insoluble silver carbonate or silver hydroxide
- 27What are the prodicts of adding nitric acid to carbonate ions and hydroxide ions?1- CO32- + 2H+ + 2NO3- ---- CO2 + H2O + 2NO3- (carbon dioxide, water and nitric acid)
2- OH- + H+ + NO3- ------ H2O + NO3- (water and nitric acid) - 28Once you have added nitric acid, what do you add next and how do you know if a silver halide has been produced?- Add a few drops of silver nitrate solution
- A silver halide precipitate will form - 29How can you differentiate between which halide has been formed?The colour of the precipitate will be different
- 30How can you tell the difference between silver bromide and iodide?Add a few drops of concentrated ammonia solution, silver bromide dissolves, but silver iodide does not
- 31Colour each one of these halide precipitates is: -silver fluoride -silver chloride -silver bromide -silver iodide1- fluoride- no precipitate
2-chloride- white
3- bromide- cream
4-iodide- pale yellow - 32Results in the further test of adding ammonia to the solution -chloride -Bromide -Iodide-chlorine- dissolves in dilute ammonia
-bromine- dissolves in concentrated ammonia
-iodide- insoluble in concentrated ammonia - 33—
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- AS - Level Chemistry (Periodicity) FlashCards sobre Group 7, criado por 12deebleabigail em 02-04-2016.
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