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?
各位CHEＭ高手,請指教
2013-03-11 2:17 am
回答 (3)
2013-03-11 5:42 am
✔ 最佳答案
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)
參考: Wiki
2013-03-11 3:13 am
I think ans of Q25 should be all of the above.
收錄日期: 2021-04-23 18:35:04
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20130310000051KK00256