concentrated H2SO4

Actually, concentrated sulphuric acid can act as an oxidizing agent when it is hot. When cool, the oxidizing power of concentrated sulphuric acid is very weak. At room temperature, concentrated sulphuric acid can be used to dry common reducing gas, and there should NOT be any redox reaction.

1. when the conc. sulpuric acid used as oxidizing agent it will change to sulphur dioxide!!! so, why not sulphur dioxide can be dried by conc. sulphuric acid??
2.conc. sulphuric acid is a strong acid so it never be used to dry basic or alkaline compound because teh acid base reaction
but for the reducing agents it will depence on whelther the redox reaction can be happened or not---- you need to check the oxidizing power---
As what I knew the conc. sulphuric acid is not strong enough to oxidize chloride ion to chlorine gas neither methane gas in gereral situation.
but is it the best drying agent for these compounds?? This is another qestion.........

2008-03-26 20:17:35 補充：
So I think the Answer 002 is not a very good answer!!!

2008-03-29 10:03:28 補充：
Qoute:
......我估你係講緊
If Chloride can be oxidized to Chlorine we can use concentrated sulphuric acid to produce chlorine gas directly....... but we never do this we always use some strong oxidizing agent to oxidize chloride (e.g. Potassium permenganate, potassium dichromate......).

2008-03-29 10:03:53 補充：
Eventually when both sulphur dioxide and chlorine gas simultaneously dissolve in water it will produce sulphuric acid and hydrochloric acid --- it means that chlorine gas can oxidize sulphur dioxide!!

2008-03-29 10:04:02 補充：
Can it be reversed in hyper-concentrated states?? I don't think so, if you say it is possible -- show the evident please don't just state it base on your wild guess!!

2008-03-29 10:06:23 補充：
Quote:
你直接將chemical直接進過 Conc.H2SO4，當然唔得。但你可以將H2SO4放係該reactant 附近.......

This is not the drying process..... in this situation con sulphuric acid only act as dessicant.....

2008-03-29 10:10:45 補充：
it means that the sulphuric acid can only absorb the water vaporized from the sample....
for the drying process it is use a chemical to take away the water from the reactant please don't mix up these 2 different concepts......

conc. H2SO4 有吸水性，所以能夠dry 到一些氣體。無錯，H2SO4 係oxidizing agent,而 SO2 係 reducing agent，但係SO2要被oxidize為SO3，要有V2O5為catalyst，而且要在高壓環境下先可以發生。由於SO2未被oxidize，conc. H2SO4 可以 dry SO2 。
conc. H2SO4唔可以dry HCl，原因為HCl入面的Cl-可以被oxide為Cl2，HCl已不存在。
conc. H2SO4亦唔可以dryCH4，因CH4可在常溫常壓下被oxidize，CH4+2O2---＞CO2+2H2O
conc. H2SO4 可以 dry alkaline 及 reducing agent ，但呢兩種野唔可以係氣體，而且呢d chemical不可以同conc.H2SO4有直接接觸。不然，兩種野都會react。

2008-03-27 23:21:45 補充：
先回應下面果句先:
As what I knew the conc. sulphuric acid is not strong enough to oxidize chloride ion to chlorine gas neither methane gas in gereral situation.
我估你係講緊Electrochemical series入面，佢本身的背景係:Ionic concentrations are 1M in water at 25°C。
而家瓶野個concentration有十幾M，與Electrochemical series的背景大相逕庭。所以你的講法不正確。

2008-03-27 23:21:49 補充：
conc. sulphuric acid is a strong acid so it never be used to dry basic or alkaline compound because teh acid base reaction，你直接將chemical直接進過 Conc.H2SO4，當然唔得。但你可以將H2SO4放係該reactant 附近，甚至吊起該chemical係H2SO4之上，唔比chemical接觸到 conc.H2SO4就可以了。conc.H2SO4係non-volatile,所以只要兩者冇接觸，都仲係可以的。