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Chemistry > Sulfur > Flashcards

Sulfur Flashcards

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1
Q

at which temperatures are rhombic and monoclinic sulfur stable?

A

rhombic is stable below 96 degrees and monoclinic is stable between 96 and 119 degrees.

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2
Q

sulfur is capable of ________

A

catenation: self linking atoms of an element to form chains and rings

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3
Q

mention 2 ways of making metal sulfides

A

heating Fe and S mixture makes FeS (Cannot be seperated using magnet).
general sulfides: passing H2S through solution with metal ion

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4
Q

how to make sulfides of Cl, O2 and F2

A

combine directly with heating
4Cl2 + S8 –> 4S2Cl2(g) disulfur dichloride
8O2 + S8 –> SO2(g) sulfur dioxide
24F2 + S8 –> 8SF6(g) sulfur hexafluoride

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5
Q

characteristics of hydrogen sulfide

A

very poisonous, dangerously flammable, smell of rotten eggs, weak dibasic acid, reducing agent, precipitant for insoluble sulfides

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6
Q

producing H2S

A

FeS + 2H+ –> H2S + Fe2+
dilute Hcl on iron(II) sulfide
(sulfides with acid)

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7
Q

hydrogen sulfide acting as a reducing agent

A

H2S is oxidised to H2O and S, K2Cr2O7 is reduced to Cr3+,,,, halogens to halide,,,, Fe3+ to Fe2+,,,, and MnO4- to Mn2+

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8
Q

show hydrogen sulfide acting as a weak acid

A

H2S + H2O –> H3O+ + HS-
HS- + H2O –> H3O+ + S2-
H2S + NaOH –> NaHS or Na2S

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9
Q

reaction when H2S is added to aq salts of p and d block metals
eg. H2S + Pb2+ –>

A

–> 2H+ + PbS

precipitate of insoluble sulfide is observed

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10
Q

tests for H2S

A

-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

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11
Q

methods of producing SO2

A

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

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12
Q

show the reaction of SO2 being reduced to S, and any conditions necessary

A

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

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13
Q

characteristics of SO2

A

reducing agent
dense gas with choking smell
anyhydride of sulphurous acid
reacts with alkalis to form sulfites or hydrogensulfites

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14
Q

how can sulfite ions be created?

A

sulfites are formed when SO2 dissolves in aq alkali

SO2+ 2OH- –> (SO3)2- + H2O

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15
Q

show the reactions involved when SO2 is bubbled through aq NaOH, and then in excess after the first product is formed

A

SO2 + NaOH –> Na2SO3 + H2O

Na2SO3 + SO2 + H2O –>2 NaHSO3

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16
Q

how is SO3 formed? gie any info on why this is used

A

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.

17
Q

how is sulfuric (IV) acid/ sulfurous acid formed?

A

SO2+ H2O –> H2SO3

18
Q

properties of sulfuric (VI) acid/ sulfuric acid

A
  • 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
19
Q

why is the temperature kept s low as possible during the contact process?

A

450degrees.

  • to not reduce reaction rate to unacceptable levels
  • fuel costs
  • corrosion of reactino chambers increases rapidly with rising teperatures
20
Q

test for sulfate ion

A

formation of white precipitate with an aq solution of Ba2+

21
Q

which are the insoluble sulfates? (solubility rule)

A

Pb2+ , Ba2+, Ag+, Ca2+, Sr2+

22
Q

show H2SO4 acting as a proton donor and displacing more volatile acids from their salts

A

H2SO4 + NaNO3 –> HNO3 + Na2SO4

23
Q

mention an exxample of H2SO4 used as a catalyst

A

esterification reactions

24
Q

examples of H2SO4 as a drying and dehydrating agent

A

drying: with CO2 and HCl
dehydrating: alcohols into alkenes and esthers into alcohols and acids

25
Q

examples of H2SO4 used as a oxidising agent

A
  • -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
26
Q

the oxoanions of sulfur

A

sulfite, sulfate, thiosulfate and peroxodisulfate (S2O82-)

27
Q

produce thiosulfate, reducing or oxidising agent?

A

boiling aq sodium sulfite soln with sulfur
Na2So3 + S(s)–> Na2S2O3 (aq)
thiosulfate is a great reducing agent

28
Q

characteristics and formation of thiosulfurous acid

A

unstable weak acid.
aq sodium thiosulfate and HCl
thiosulfurous acid disproportionates
S2O32- + 2H+ –> H2S2O3 –> S + SO2+ H2

29
Q

reaction of thiosulfate with aq iodine

A

2S2O3 2- + I2 –> S4O6 2- + 2I-

thiosulfate ion –> tetrathionate ion

30
Q

give industrial use of thiosulfate and reaction

A

to remove excess Cl from fabrics after bleaching. chlorine oxideses thiosulfate to sulfates
5H2O + S2O3 2- + 4Cl2 —> 8Cl- + 2SO4 2- + 10H+

31
Q

overall reactions of the contact process: making of H2SO4

A

SO2 + O2 —> SO3
SO3 + H2SO4 —> H2S2O7
H2S2O7 + H2O —-> H2SO4

32
Q

two methods of making S2Cl2

A
  • chlorine combines with S8 directly on heating

- CS2 + 3Cl2 –> CCl4 + S2Cl2

33
Q

preparation of SOCl2 (thionyl chloride)

A

SO2 + PCl5 —> SOCl2 + POCl3

34
Q

preparation of CS2

A

direct combination of C and S at high temperatures

35
Q

test for thiosulfate ions

A

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

36
Q

colour of sulfur flame

A

blue flame

Chemistry (11 decks)

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