[DSE化學2018]同學準備好DSE CHEM未? (3)

請問2013 mc q16呢類題有冇較快既方法?
我用開答案代入法去判斷合唔合理
有冇更快既方法?

14 an chem 3c
就咁t同埋NaHCO3+acid 唔係已經有2 layer咩
點解要加pentane去溶t嘅

想問電解 陰極個到
係咪唔洗理Fe3+ 我見佢都係h+下面

Why acidified potassium permanganate can oxidize alkene into alkanol, but dichromate cannot?
Or just my textbook doesn’t show
搵左好耐都淨見permanganate, 唔見有講dichromate

想問下2,4-dinitrophenylhydrazine 可唔可以就咁寫成2,4-DNP

Ethene+ cold acidified potassium permanganate + H2O —> ethanol

Ethene is said to be oxidized, why?

Gaining hydrogen is reduction, gaining oxygen is oxidation, both situations occur at this reaction,
Why and how do we judge this situation

Another question, if in terms of oxidation number,
It seems that no oxidation number of atoms in ethene has been changed

Acid 同nahco3 react完除左co2仲有其他product 你要分隔埋佢地

Dichromate 的確唔得 因為佢無permanganate 咁strong既oxidising power

其他product唔係都會溶係aqueous layer ？

synthetic route係咪一定要寫heat/reflux？

no

睇返我有教用氧化數bal
https://youtu.be/Dj77iUbzLlw
唔好代答案 通常都會慢同易錯
同埋佢某d unknown唔比你就無得代

有時個sample含量可以好少 變左你個organic layer會好薄 好難分出黎

唔洗理

Cr2O72-個oxidizing power唔足夠oxidize C=C
HKEA唔accept用Cr2O72-去氧化C=C

yea

yes

in general 每gain一個O 個ON +2
每gain一個H 個ON -1
唔係就咁睇多O定多H 要睇下大家個比例
我會話呢d情況用返ON change去判斷會好d

睇你咩reaction
直樓睇返HKEA official 個requirement (last page)
http://www.edb.gov.hk/attachment/en/curriculum-development/kla/science-edu/ref-and-resources/Supplementary_note_for_Chem_30Oct2015_e.pdf

Ethene converts into ethanol, gaining 2 oxygen and 2 hydrogen
啫係話ethene 嘅oxidation number changes from 0 to 2?

唔好意思，chem有啲渣

淨heat with OH-就出NH3
佢果度steap 2加返H+

C2H4 -> C2H6O2
ON of C = -2 -> -1