Re: RE:speed of reaction -- Chemistry

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Date Posted: 19:35:25 11/04/01 Sun
Author: Mr. Yeo Woei Ter
Subject: Re: RE:speed of reaction
In reply to: Lim Yee Lian 's message, "RE:speed of reaction" on 01:01:31 11/04/01 Sun

I think you changed the question a little.

You have to specify which reagent is in excess, the hydrochloric acid or zinc powder?

If in the first reaction, the acid is in excess, then the volume of hydrogen gas collected in both experiment will be the same if we use the same mass of zinc powder.

However, the speed of reaction with sulphuric acid will be faster. Because sulphuric acid is a dibasic acid, so it will have a higher concentration of H⁺ ions.

HCl(aq) ---> H⁺(aq) + Cl^-(aq)
H₂SO₄ ---> 2H⁺(aq) + SO₄^2-(aq)

So one mole of HCl produces 1 mole of H⁺ ion
whereas one mole of H₂SO₄ produces 2 moles of H⁺ ions.

So if the concentration of HCl and H₂SO₄ is both 1 mol/dm³, then the concentration of H⁺ ion in sulphuric acid will be double that in hydrochloric acid.

Hope that answer your question!

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Replies:

[> [> Re: RE:speed of reaction(THANK U) -- Lim Yee Lian, 04:32:59 11/08/01 Thu

HI MR YEO
Thanks for ur reply.. ur prmpt reply has helped me greatly...The "O" level exam came out an exactly same question i ask u ..... Those who have seen my question will defintely benefit too...
Thank u SO MUCH!!

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[> [> [> Re: RE:speed of reaction(THANK U) -- Mr. Yeo Woei Ter, 06:16:18 11/10/01 Sat

Hi there!

The 'O' level question uses excess zinc, so it's a bit different. So the volume of hydrogen should be double for sulphuric acid.

However, the speed of reaction will still be faster for sulphuric acid because it has a higher concentration of H⁺ ion.

Hope you got it right!

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