Sulfur Flashcards
at which temperatures are rhombic and monoclinic sulfur stable?
rhombic is stable below 96 degrees and monoclinic is stable between 96 and 119 degrees.
sulfur is capable of ________
catenation: self linking atoms of an element to form chains and rings
mention 2 ways of making metal sulfides
heating Fe and S mixture makes FeS (Cannot be seperated using magnet).
general sulfides: passing H2S through solution with metal ion
how to make sulfides of Cl, O2 and F2
combine directly with heating
4Cl2 + S8 –> 4S2Cl2(g) disulfur dichloride
8O2 + S8 –> SO2(g) sulfur dioxide
24F2 + S8 –> 8SF6(g) sulfur hexafluoride
characteristics of hydrogen sulfide
very poisonous, dangerously flammable, smell of rotten eggs, weak dibasic acid, reducing agent, precipitant for insoluble sulfides
producing H2S
FeS + 2H+ –> H2S + Fe2+
dilute Hcl on iron(II) sulfide
(sulfides with acid)
hydrogen sulfide acting as a reducing agent
H2S is oxidised to H2O and S, K2Cr2O7 is reduced to Cr3+,,,, halogens to halide,,,, Fe3+ to Fe2+,,,, and MnO4- to Mn2+
show hydrogen sulfide acting as a weak acid
H2S + H2O –> H3O+ + HS-
HS- + H2O –> H3O+ + S2-
H2S + NaOH –> NaHS or Na2S
reaction when H2S is added to aq salts of p and d block metals
eg. H2S + Pb2+ –>
–> 2H+ + PbS
precipitate of insoluble sulfide is observed
tests for H2S
-test with dichoromate (reducing agent)
- a filter paper dipped in aq lead(II) ethanoate turns black when in contact with H2S
H2S +Pb2+ –> H+ + PbS
methods of producing SO2
1) conc H2SO4 heated with copper turnings
2) acid on a sulfite Na2SO3 + HCl–> SO2 + NaCl+ H2O (acidifying sulfites into sulfur dioxide)
3) burning sulfur compounds ZnS + O2 –> SO2+ ZnO
show the reaction of SO2 being reduced to S, and any conditions necessary
2H2S + SO2–> 3S + 2H2O
the gases cannot be dry as sulfur deposits in the moist parts of the gas. this shows that H2S is a stronger reducing agent than SO2
characteristics of SO2
reducing agent
dense gas with choking smell
anyhydride of sulphurous acid
reacts with alkalis to form sulfites or hydrogensulfites
how can sulfite ions be created?
sulfites are formed when SO2 dissolves in aq alkali
SO2+ 2OH- –> (SO3)2- + H2O
show the reactions involved when SO2 is bubbled through aq NaOH, and then in excess after the first product is formed
SO2 + NaOH –> Na2SO3 + H2O
Na2SO3 + SO2 + H2O –>2 NaHSO3
how is SO3 formed? gie any info on why this is used
by oxidation of SO2 using vanadium V oxide at 450 degrees celcius. a low temp adn high pressures would be best, but at high pressures SO2 liquefies and at low temp the rate is too slow. the catalyst is employed. pressure is kept high enough to ensure flow of reactants but not enough for liquification. this is used in the contact process.
how is sulfuric (IV) acid/ sulfurous acid formed?
SO2+ H2O –> H2SO3
properties of sulfuric (VI) acid/ sulfuric acid
- viscous, covalent, and high bp, due to H bonding
- strong acid
- drying agent (not basic gases) (conc)
- dehydrating agent (conc)
- oxidising agent (hot conc)
- sulfonating agent
- catalyst
- proton donor capable of displacing more volatile acids from their salts
why is the temperature kept s low as possible during the contact process?
450degrees.
- to not reduce reaction rate to unacceptable levels
- fuel costs
- corrosion of reactino chambers increases rapidly with rising teperatures
test for sulfate ion
formation of white precipitate with an aq solution of Ba2+
which are the insoluble sulfates? (solubility rule)
Pb2+ , Ba2+, Ag+, Ca2+, Sr2+
show H2SO4 acting as a proton donor and displacing more volatile acids from their salts
H2SO4 + NaNO3 –> HNO3 + Na2SO4
mention an exxample of H2SO4 used as a catalyst
esterification reactions
examples of H2SO4 as a drying and dehydrating agent
drying: with CO2 and HCl
dehydrating: alcohols into alkenes and esthers into alcohols and acids
examples of H2SO4 used as a oxidising agent
- -metals oxideised to sulfates–> Zn+ H2SO4–> ZnSO4 +H2
- -non metallic elements into oxides C+H2SO4–>CO2 +SO2 +H2O
- -halide to iodine H2SO4+ KI –> HI + KHSO4
the oxoanions of sulfur
sulfite, sulfate, thiosulfate and peroxodisulfate (S2O82-)
produce thiosulfate, reducing or oxidising agent?
boiling aq sodium sulfite soln with sulfur
Na2So3 + S(s)–> Na2S2O3 (aq)
thiosulfate is a great reducing agent
characteristics and formation of thiosulfurous acid
unstable weak acid.
aq sodium thiosulfate and HCl
thiosulfurous acid disproportionates
S2O32- + 2H+ –> H2S2O3 –> S + SO2+ H2
reaction of thiosulfate with aq iodine
2S2O3 2- + I2 –> S4O6 2- + 2I-
thiosulfate ion –> tetrathionate ion
give industrial use of thiosulfate and reaction
to remove excess Cl from fabrics after bleaching. chlorine oxideses thiosulfate to sulfates
5H2O + S2O3 2- + 4Cl2 —> 8Cl- + 2SO4 2- + 10H+
overall reactions of the contact process: making of H2SO4
SO2 + O2 —> SO3
SO3 + H2SO4 —> H2S2O7
H2S2O7 + H2O —-> H2SO4
two methods of making S2Cl2
- chlorine combines with S8 directly on heating
- CS2 + 3Cl2 –> CCl4 + S2Cl2
preparation of SOCl2 (thionyl chloride)
SO2 + PCl5 —> SOCl2 + POCl3
preparation of CS2
direct combination of C and S at high temperatures
test for thiosulfate ions
on addition of dilute acid (usually HCl), the unstable weak thiosulfurous acid forms and disproportionates into SO2 and S. S forms a white pp and SO2 is a pungent gas that can be tested with dichromate paper
colour of sulfur flame
blue flame
