dindin asked in 科學及數學化學 · 8 years ago

各位CHEM高手,請指教

Q25

Which of the following processes would produce sulpur dioxide?

(1)Roasting iron pyrite in air

(2)Heating zinc with concentrated sulphuric acid

(3)Mixing dilute hydrochloric acid with sodium sulphite.

Why the ans should be (2) and (3)?

Q30

Statement 1:

Carbon can form a large number of compounds with long carbon chains.

Statement 2:

Carbon atoms can share electrons with one another.

Why statement 2 is not a correct explanation of statement 1?

Q40

When 10g of PURE calcium carbonate(molar mass=100.1g) reacted with excess hydrochloric acid,24 dm^3 of carbon dioxide was obtained at room temperature and pressure.However,in a similar experiment using 10g if IMPURE calcium carbonate,2.5dm^3 of carbon dioxide was obtained.Assuming that impurity is a metallic carbonate,what would this impurity be?

A.MgCO3

B.ZnCO3

C.FeCO3

D.CuCO3

ANS :A

How to find out the ans?

3 Answers

Rating
  • 8 years ago
    Favorite Answer

    Q25:

    (1) is incorrect because according to Wiki,"Thermal decomposition of pyrite into FeS (iron(II) sulfide) and elemental sulfur starts at 550 °C" so it cannot form SO2 when reacting with oxygen in air.

    (2) is correct because conc.H2SO4 is strong oxidizing agent and will oxidize zinc and itself being reduced into SO2.

    The chemical equation is:Zn + H2SO4 + 2H+ -> Zn2+ + SO2 + 2H2O

    (3) is correct because NaSO3 + H2SO4 -> NaSO4 + H2O + SO2

    Q30:

    statement 2 is not the explanation of statement 1 because the ability of carbon to form mutiple bond with other atoms is not due to the ability to form covalent bond(as many non-metal also has this property) but owing to catenation. By Wiki again,"The ability of an element to catenate is primarily based on the bond energy of the element to itself, which decreases with more diffuse orbitals (those with higher azimuthal quantum number) overlapping to form the bond. " I do not understand what it means, maybe the others helpful can help.

    Q40: As more volume of carbon dioxide is given out, it shows that the impurity has less molar mass compared to Ca. Among four choices, only Mg(molar mass=24gmol-1) is lighter than Ca(molar mass=40gmol-1)so the answer is A.The calculation is not needed.(also I don't know)

    Source(s): Wiki
  • 8 years ago

    Chem Use ?

    =======>23

    Che mu se

    Source(s): Chem Use 23
  • ?
    Lv 7
    8 years ago

    I think ans of Q25 should be all of the above.

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