Daiva

1. six compounds are classified into two groups as down in the table below:
gas :                                                      solid:                                               
ammonia                                                iron(III) oxide        
carbon dioxide                                        magnesium oxide
nitrogen dioxide                                      potassium oxide
reclassify these compunds into two groups according to:
(a) one of their physical properties and
(b) one of their chemical properties.



2 a student proposed that following methods to accomplish three tasks.(a),(b)and,(c).
the proposed methods were all considered inappropriate
(a) task: to neutralize acidic soil in a Flower bed
proposed method: add solid sodium hydroxide to soil.
(i) state one reson thy the method is inappropriate.
(ii)suggest an appropriate method to accomplish the task.



(b) Task: To prepare hydrogen gas from an acid.
proposed method: add copper to dilute hydrochloric acid.
(i)state one reason why the method is inappropriate.
(ii)suggest an appropriate method to accomplish the task.


(c)task: to dilute concentrated sulphuric acid with water
proposed method: add water to concentrated sulphuric acid stir the mixture.
(i)state one reason why the method is inappropriate.
(ii)suggest an appropriate method to accomplish the task.







3 concentrated sulphuric acid can be used as a toilet bowl cleaner. However, many toilet bowl cleaner contain granular sodium hydrogensulphate(NaHso4) as th active ingredient instead of concentrated sulphuric acid.
(i) write the chemical equation equation for the formation of sodium hydrogensulphate from sulphric acid.
(ii) state one advantage of using granula sodium hydrogensulphate aver using concentrated sulphuric acid as a toilet bowl cleaner

[ 本帖最後由 Daiva 於 2010-5-17 06:59 PM 編輯 ]

Daiva

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桃子

>>NaHSO4 not corrosive in absence of water

NaHSO4 is a corrosive solid.
This is due to its hygroscopic and acidic properties.

桃子

NaHSO4 is hygroscopic and absorbs water readily.
It is very dangerous to touch it with your hand.

桃子

引用:

原帖由 ch252525 於 2010-5-18 10:18 PM 發表
I remembered CE marking said it is not corrosive in absence of water is correct...

Which year???

桃子

I've just checked it.
It is 2006 Q3(b) and the marking scheme is as follows.


This is a sensible answer.

Daiva

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