回應(會考化學)

回應

Maryuen:
(6)2004 past paper 9cii2can i use water?

(7)What is duralumin?

(8) 2003 past paper 3biwhat is formula unit stated in the marking scheme?

(9) HBr and conc. H2SO4是什麼reaction?

(10) conc. H2SO4和sugar的reaction observation要write "the heat produced expand air inside the black carbon and rise it up"嗎??

(11) conc. H2SO4 used in the preparation of HCl and HNO3 acid out c了嗎??

(12) H2SO4 ionizes in water to give H3O+(aq) ions??

(13) H2SO4的half equation到底是什麼??

化學友:
(6) 唔得o架，一定要H+。因為只有H+先會react with RCOO- (RCOO- + H+ --> RCOOH)

(7) duralum係由aluminium做成嘅alloy(合金)，佢比aluminium more corrosion resistant同埋stronger。

(8) e o個term可以唔使識o架，其實你唔使學佢咁做，用你平日計mole嘅方法做就得o架喇。

(9) maryuen，你o向邊度見到e o個reaction? 照計out out地syllabus。不過寫比你睇下:

2HBr + H2SO4 --> Br2 + SO2 + 2H2O

e o個係redox reaction(因為Br嘅O.N.由-1 change to 0; 而S嘅O.N.由+6 change to +4)

(10) 一般會考答案唔係咁寫，你只要寫成咁就得喇:

i. sugar chars (sugar turns from white to black)

ii. misty fume(H2O(g) is given out

(11) out左喇

(12) 你可睇o下下面回覆pele159嘅答案，你地問緊同一樣o野呀。

(13) H2SO4 + 2H+ + 2e- --> SO2 + 2H2O 或者 4H+ + SO42- + 2e- --> SO2 + 2H2O
第一條accurate d 但會考兩條都接受。