maryuen:
1. 我想知道什麼時候有depolymerizaton and 它是怎麼發生的??(有沒有example,會考有沒有機會出??)
2. 另外..2001 past paper 5那個anodization要不要寫eletrode的名?? sacrificial protection要寫example嗎??是不是所有essay都要有引入??
化學友:
1. maryuen,其實depolymerization o向近年嘅CE chem都好少好少出o架,化學友覺得就算出都會好容易嘅。你只要當佢係polymerization嘅相反就得o架o拉。例如:
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh_TvuHrZAtFaisHzH85bqb2d2H9hgzY2pfBZOPLTe6uQBlNFDE34nbAIY8tYXxgUjKUoWI-2nUu08oUl9NkhUY5kyfsWt6NyORbcyQkX8hwSo91IZ3HOJdQw_fUH9BLymy3Y4fMYR_Alg/s400/depoly.jpg)
睇到嗎maryeun o個reaction只係polymerization嘅相反。至於reaction conditions,一般都係high temperature同埋in the absence of air(否則d polymer會burns) 。
2. 2001 Paper I 5 : Explain why anodization, sacrificial protection and tin-plating can protect metals from corrosion. (9 marks)
maryuen,其實寫唔寫都冇問題o架,因為anodization一定係將aluminium做anode,所以唔都ok。2005嘅marking就冇要求你寫example,但係有時你唔知邊一年marking要寫example,所以化學友suggest你o向考試寫埋啦。CE chem嘅essay係唔使寫引子o架,一般9分嘅題目你寫夠6個points(6分)就滿分o架啦(其餘3分就係communication分)。關於essay嘅detail information,遲一、兩日再講比大家知丫。maryuen唔明再問我啦。
回應2
sinying:
1. 唔好意思........我想問ionization 同埋dissolve in water係點分架?HCL 係dissolve water 定ionize???咁NACL呢?
2. 我仲想問呢....Al2O3都係dehydrating agent 來的嗎?仲有d咩compond 係dehydrating agent呀??THX!!
化學友:
1. sinying,化學友唸你對一隻substance dissolves in water嘅方法唔係太了解。其實一隻substance dissolves in water係有唔同嘅途徑,下面係CE chem常見嘅,例如:
i. sugar溶落水。sugar只係simply dissolves in water,佢同水冇化學反應,溶之前佢係exist as sugar molecule,溶之後佢都係exist as sugar molecule。
ii. Na(s)溶落水。Na加落水時,Na同水產生化學反應生成NaOH(s)。而NaOH(s)係溶o向水to give NaOH(aq),所以Na溶水係因為佢同水有化學反應。
iii. NaCl(s)溶落水。NaCl(s)裡面o個d Na+ ion同埋Cl-ion溶之前係 not mobile嘅,溶之後Na+ ion同埋Cl-ion變左mobile,同sugar一樣佢同水冇化學反應。
iv. HCl(g)溶落水。HCl(g)溶之前佢係exist as HCl molecule,溶之後發生ionisation:HCl --> H+ + Cl-,而H+同埋Cl-都係溶落水嘅。
簡單o黎講dissolve in water同ionisation冇乜關係,只不過有時一隻substance溶落水會發生ionisation咋。好似HCl咁,佢溶落水時會發生ionisation。
2. 凡親一隻substance可以將某一compound裡面嘅H同O remove 變成H2O, 佢就可以叫做dehydrating agent。CE chem syllabus裡面當我地剩係知遒conc. H2SO4係dehydrating agent,其他o個d dehydrating agent係唔使記,只要我地o向考試時見到隻substance可以將一隻compound嘅H2O remove,佢就係dehydrating agent o架喇。例如,
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvGqOdy8wpF2qgXNNJTy60tbgYESisip2dbGz3LYNA7xsVQJkAIDaglQn4RjMymrEBhLkFqfrHsCZz5y04pphFWwy_kzKeDCg8iLKL7J0GKkR3shfUQIElirMCeAYVJl4SxH4K13o-ybc/s400/Doc2.jpg)
根據上面嘅定義,conc.H2SO4, Al2O3同埋P2O5都係dehydrating agent。唔使死記o架。答唔答到你呀sinying?
1 則留言:
你好 我有少少問題
1. 請問 detergent 有 branch 係咪唔 可以溶在水 ??
不過點 g 稱為有 branch ??
2. solid citric acid 點解可以 turn moist blue litmus paper red ??
3. 請問整soap 中的 NaOH/H2SO4 係咪catalyst ??我呀sir 話係,不過我問同學,佢地又say no
4. Refer to 03 第9(a)題
如果the inert electrode A is copper plate , the B is zinc rod .Sulphur is ZnSO4, sodium is CuSO4
In what the direction would the sulphate ion pass through the porus pot ? Explain your ans .
你可否比一比你個e-mail 我 ??
我有圖但唔識 upload,問唔到 ....
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