F.4 Chem分NaCI, NaOH,NH4Cl

👨🏻‍🏫 學術台化學

Wong Q

2009-02-25 5:07 am

問題問有3個unlabelled bottles, each containing white solid,呢3個bottles 有可能contain>
Sodium chloride
Sodium Hydroxide
Ammonium Chloride

Suggest the procedure to identify the contents of each bottle, using the following materials:
Distilled Water
Test Tubes and Beakers
Bunsen Burner
Red Litmus paper

your ans should include the observation of each test.

我想問下我呢個諗法岩唔岩>
put the solids into the distilled water先(to show alkaline properties?)
再drop d solution 去red litmus paper 度,轉blue 係Sodium Hydroxide

sodium chloride 同ammonium chloride 我真係唔知點分-_-
可唔可以用bunsen burner test sodium 既golden yellow flame?
同埋我想問下ammonium chloride 係咪neutral?

希望可以詳細少少解下.. thank you!!!!!

更新1:

Ammonium chloride sublimes on heating, because it decomposes to give ammonia gas and hydrogen chloride gas. NH4Cl(s) → NH3(g) + HCl(g) Sodium chloride remains unchanged on heating. <<< 我想問下呢d 係咪F.4 應該既concept? 因為我印象中好似未學過... 同埋係咪得呢個方法?

更新2:

係呀我地都有教ammonium + Hydroxide 而且heat埋出ammonia... 但我唔知ammonium 單丁一個heat 都出到ammonia >_< 唔該哂唔該哂兩個答案都好好搞到我都唔知點簡

回答 (2)

老爺子

2009-02-25 6:07 am

✔ 最佳答案

In three test tubes, dissolve separately the three solid samples in water to form corresponding aqueous solution. Test each solution with red litmus paper, only sodium hydroxide changes the blue litmus paper to red. This is because only sodium hydroxide is alkaline due to the presence of hydroxide ions in the solution.

Put separately each of the rest two solid samples in test tube, and then heat with a Bunsen burner. Ammonium chloride sublimes on heating, because it decomposes to give ammonia gas and hydrogen chloride gas.
NH4Cl(s) → NH3(g) + HCl(g)
Sodium chloride remains unchanged on heating.

(You may identify sodium chloride by golden yellow flame in flame test, if platinum wire or nichrome wire is provided.)
=

👍 0 👎 0

hongkei

2009-02-25 6:59 am

ammonium chloride應該係acid。
因為NH3加水之後，會變weak base，
NH3 + H2O ---> NH4+ + OH-
因為係WEAK BASE，姐係 NH3唔TEND TO 變成 NH4+，
雖然都有部分會變。

而REVERSE呢個理論，NH4+係會TEND TO 變翻 NH3，
呢個就係點解 HEAT之後你可以有呢條式：
NH4Cl(s) → NH3(g) + HCl(g)

不過就算NH4+就咁同H2O一齊，
都會比咁Ｄ H+ IONS個SOLUTION，
所以會係acidic 。

不過其實呢個concept有少少難，雖然Ｄ野全部都係中四野，
但係課程好似，好似係無，
可能你老師唔會比。

其實試完NaOH之後，你再燒燒 d solid 睇下邊個係golden yellow就得架啦。（燒係燒solid架。）

2009-02-24 23:03:35 補充：
如果我無記錯既話，中四教關於ammonia出gas應該係教，
加alkalies出NH3：
NH4+ + OH-
-->
NH3 +H2O

2009-02-24 23:07:22 補充：
睇完上面人兄既答案我都覺得佢比少左platinum wire or nichrome wire你，
不過如果你監硬要屈佢既話，你話要就咁放係張桌到燒都得架，我講得佢應該係講少左架姐…

應該無可能係用上面哥個咁難既方法既…

p.s.佢打火機都無比你啦，咁咪開唔到burner??

👍 0 👎 0

收錄日期: 2021-04-29 18:17:59
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20090224000051KK01808

檢視 Wayback Machine 備份