chem practice paper Qns

2012-01-22 5:03 am

圖片參考：http://imgcld.yimg.com/8/n/HA08059003/o/701201210063213873422491.jpg

6c. since molecules of C pack more compactly than D. so C has a higher Van der waals' force and a higher boiling pt, and thus a higher density?
6d. D. because D has the lowest density,???(不太懂這條),有4 Marks

8b. No mobile ions??

9a. 不用
9b. metal oxide is alkaline while non-metal oxide is acidic?
9c. Add HCl into the oxides,only Mgo and Al2O3 will give a colourless solution(a neutraliztion occurs). this show that MgO and Al2O3 is alkaline.
Add NaOH into the remaining 3 oxides,only SO2 and P4O10 can react with NaOH to give a colourless solution. so SO2 and P4O10 is acidic. The last one is amphoteric.(應該不對)

更新1:

9b.是一分,哪是答哪句?---> metal oxide is alkaline while non-metal oxide is acidic? 9c. 雖然我是這樣寫去分SO2 和P4O10,但我覺得好像不對,SO2 和P4O10溶左落水,再+NAOH也只不過是colourless SOLUTION,但NAOH本身也是colourless solution.其實我們是不是不知他們是反應了???

回答 (5)

ShingMingTony

2012-01-22 6:01 am

✔ 最佳答案

6.c. Yes. In D the -OH is bonded to the 2th carbon, which is just like a branch chain. More branched molecules pack less efficient. As strength of Van der Waal's force decrease when the distance between molecules increase(If you study physics, you can refer to Columb force). efficient packing lead to high density, while stronger Van der Waal's force give higher b.p..

6d. I suggest F. From its highest b.p. among three, its Van der Waal's force should be the strongest. So its viscosity will be the highest too.

8b. Correct

9b. Something like that. Metal oxides are ionic compound and usually give out oxide ions in neutralization, so they show alkaline property. Oxygen atom in non-metal oxide are covalently bonded and are not easy to be separated from the molecules. Instead, due to the high electronegativity of oxygen atom, non-metal oxides tend to form anion of an acid.

9c. Correct for neutralization of metal oxides and the amphoteric one. But SO2 and P4O10 is needed to be dissolved in water first before the test or else no acid properties will be shown.

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小云

2012-01-23 1:14 am

氫鍵越多　viscosity越高
所以濃硫酸viscosity很強（氫鍵）
濃H3PO3　viscosity也很強　（氫鍵）

viscosity越高　阻力越高　所以沉下去的時間較長

2012-01-22 17:26:03 補充：
9c)
MgO　alkaline
SO2 P4O10 SiO2 acidic
Al2O3 amphoteric

分別加入HCl NaOH 進每一個溶液
只有MgO和Al2O3　和HCl反應

而只有SO2 P4O10 SiO2 Al2O3　和 NaOH反應

所以MgO alkaline
SO2 P4O10 SiO2 acidic
Al2O3 amphoteric

請注意SiO2是酸性的　它會和NaOH反應形成粘結劑
所以不能用由SiO2做成的玻璃蓋去蓋NaOH(aq)
因為它們反應後，粘結劑形成，蓋會不能打開

2012-01-22 17:39:23 補充：
9b)　離子鍵含氧化合物就具有鹼性　（AI2O3是兩性，但它的確具有鹼性）（但不否定它也具有酸性）
共價鍵含氧化合物就是酸性

2012-01-22 17:46:25 補充：
多送一條方程給你
SiO2+2NaOH -->Na2SiO3 + H2O
Na2SiO3就是粘結劑
可能你會奇怪
SiO2不溶水　又不具有H+
它怎會是酸性呢？
中和作用有一種定義是
酸接收O原子，鹼提供O原子
SiO2作酸接收O原子　NaOH作鹼提供O原子
所以 OH- 接供O 而 SiO2　接收O
形成H+ SiO3^2- 另一個OH-和H+反應
所以生成Na2SiO3+H2O

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[匿名]

2012-01-22 5:57 pm

但是知道多少個H-BOND FORM左,就知道誰跌下去先嗎??不明白這條

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