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monokekie

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sulfuric acid reactions
« on: August 19, 2009, 11:23:48 PM »
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heya guys, there's a question stuck in my mind atm,

does dilute sulfuric acid and concentrated sulfuric acid react differently with particular substances? as in, does sulfuric undergo different reactions with a thingo depending on their concentration?


i saw these info:

      when sulfuric concentrated:
        sulfuric reacts with zinc to produce SO2, S and H2S

      when they are diluted:
        reacts with zinc to form ZnSO4, reacts with magnesium to form MgSO4, reacts with Fe to form  FeO4,       
        reacts with NaOH to form Na2SO4
     


whywhywhywhywhywhy??????

Offline TrueTears

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Re: sulfuric acid reactions
« Reply #1 on: August 20, 2009, 04:17:33 PM »
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Sulfuric acid does indeed react with zinc to form those 3 substances, each formula has products as and but the only difference is , S and . To form these 3 different substances, it depends on the temperature, concentration and other reaction conditions.
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monokekie

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Re: sulfuric acid reactions
« Reply #2 on: August 20, 2009, 06:33:21 PM »
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Sulfuric acid does indeed react with zinc to form those 3 substances, each formula has products as and but the only difference is , S and . To form these 3 different substances, it depends on the temperature, concentration and other reaction conditions.
oooh tkx for summing that up for me.TT =D

but how do we tell hows sulfuric acid gonna react by just looking at its conditions? sulfuric is involved in too many reactions. ( i know this question is quite broad  and is quite hard to explain) but how do we distinguish which falls within which category and how it happens?

arh, do we really needa no that stuff?

Offline Mao

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Re: sulfuric acid reactions
« Reply #3 on: August 20, 2009, 11:34:55 PM »
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There are four ways sulfuric acid can react, these mainly depend on the amount of reactants available, and how concentrated sulfuric acid is. You are not expected to judge which reaction will take place, as they usually all react to a certain extent. If you need to balance an equation, the question will tell you what key product is formed.

H2SO4(aq) + Zn(s) --> ZnSO4(aq) + H2(g), this reaction usually take place in solutions (i.e. not pure or highly concentrated H2SO4)
2H2SO4 + Zn --> ZnSO4 + SO2 + 2H2O, half eqn SO4 2- + 4H+ + 2e- --> SO2 + 2H2O
4H2SO4 + 3Zn --> 3ZnSO4 + S + 4H2O, half eqn SO4 2- + 8H+ + 6e- --> S + 4H2O
5H2SO4 + 4Zn --> 4ZnSO4 + H2S + 4H2O, half eqn SO4 2- + 10H+ + 8e- --> H2S + 4H2O
The above three occur with extremely strong solutions of sulfuric acid. The extent of each reaction depends on the amount of metal available. Note that zinc can be replaced by other metals.
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monokekie

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Re: sulfuric acid reactions
« Reply #4 on: August 20, 2009, 11:38:29 PM »
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There are four ways sulfuric acid can react, these mainly depend on the amount of reactants available, and how concentrated sulfuric acid is. You are not expected to judge which reaction will take place, as they usually all react to a certain extent. If you need to balance an equation, the question will tell you what key product is formed.

H2SO4(aq) + Zn(s) --> ZnSO4(aq) + H2(g), this reaction usually take place in solutions (i.e. not pure or highly concentrated H2SO4)
2H2SO4 + Zn --> ZnSO4 + SO2 + 2H2O, half eqn SO4 2- + 4H+ + 2e- --> SO2 + 2H2O
4H2SO4 + 3Zn --> 3ZnSO4 + S + 4H2O, half eqn SO4 2- + 8H+ + 6e- --> S + 4H2O
5H2SO4 + 4Zn --> 4ZnSO4 + H2S + 4H2O, half eqn SO4 2- + 10H+ + 8e- --> H2S + 4H2O
The above three occur with extremely strong solutions of sulfuric acid. The extent of each reaction depends on the amount of metal available. Note that zinc can be replaced by other metals.

oh okay, i get it now.

thanks for your help Mao!!!