thisbetterhelpme
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"Sodium bromide reacts with concentrated sulfuric acid in a different way from sodium chloride. Write an equation for this reaction of sodium bromide."
The markscheme says: 2NaBr + 2H2SO4 --> Na2SO4 + Br2 + SO2 + 2H2O
Can someone please explain why it's Na2SO4 and not NaHSO4?
Last edited by thisbetterhelpme; 1 month ago
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gogrizz123
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(Original post by thisbetterhelpme)
"Sodium bromide reacts with concentrated sulfuric acid in a different way from sodium chloride. Write an equation for this reaction of sodium bromide."
The markscheme says: 2NaBr + 2H2SO4 --> Na2SO4 + Br2 + SO2 + 2H2O
Can someone please explain why it's Na2SO4 and not NaHSO4?
otherwise you wouldnt have enough hydrogens, you would have 4 on the LHS and 5 on the RHS with a spare Na on the RHS
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simxne_
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I thought of a substitution reaction, so thought: NaBr + H2SO4 --> NaHSO4 + HBr.
But it seems that the bromide ions are strong reducing agents and so reduce the H2SO4 to SO2. The bromide ions will then oxidise to bromine.

This redox reaction won't happen with NaCl or NaF.
I don't know if that's what you were looking for, but hope it's helps.
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ineedhelpsohelp
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(Original post by thisbetterhelpme)
"Sodium bromide reacts with concentrated sulfuric acid in a different way from sodium chloride. Write an equation for this reaction of sodium bromide."
The markscheme says: 2NaBr + 2H2SO4 --> Na2SO4 + Br2 + SO2 + 2H2O
Can someone please explain why it's Na2SO4 and not NaHSO4?
You work it out using ionic equations IE: 2Br- ---> Br2 + 2e- and SO42- -----> SO2 +2e- (Combine the ionic equations and it'll give you the overall equation) Also, there's multiple equations that you can give. Using ionic, you should get 3H2SO4 I'm pretty sure.

There's also another way you can work it out by combining 2 different equations together. I don't remember it off the top of my head though. Those were the two ways we were taught. Hope this helps!
Last edited by ineedhelpsohelp; 1 month ago
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thisbetterhelpme
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Thanks everyone!! It was just that I'd done a similar question before and NaHSO4 was always the product from the initial acid-base reaction - i hate it when markschemes conflict:confused:
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