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Magnesium + Hydrochloric Acid Reactions

Q. Hi, I'd like to know more about how copper sulphate [this product on eBay or Amazon affil links] affects the reaction between magnesium and hydrochloric acid. It's for a school project--help!

Rachel J [last name deleted for privacy by Editor]
- London, UK


A. Hiya. Don't know much apart from the fact that it catalyses the reaction, presumably by forming some some of complex. Copper is good at forming complexes - being a transition metal, and having a variable oxidation state. That's about all I know. I've done the reaction just to show copper as a catalyst, and it works really well, but not the details of the exact nature of how it works.

Q. Was hoping for salvation myself -- reaction of Mg and acid. Why is it that Mg ribbon that has been cleaned reacts much slower with acid that Mg ribbon with a layer of oxide on it? And it does - very noticeable. I would have thought it would be the other way around? Any ideas?

DAVE B [last name deleted for privacy by Editor]
- London

A. I believe it has to do with the activation energy required for the particles to bond. The Oxidization of the magnesium provides the alternate means for the reaction to occur. Instead of the HCl just reacting with the raw magnesium, the oxidized magnesium is weakened. I'm not a 100% sure, I was just doing a chem lab on this reaction and found this site. Hope this helps.

Hilary A [last name deleted for privacy by Editor]
- London, Ontario

Multiple threads merged: please forgive chronology errors :-)

Magnesium Ribbon

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Q. Does anyone know where I can find out any information on the Magnesium and acid reaction? Its for my a-level practical.

Michael F [last name deleted for privacy by Editor]
- England

Q. I am 2 years below my gcses and I'm doing this practical at gcse standard, I would be grateful for any help!

Louise [last name deleted for privacy by Editor]
- Cambs

A. So Mg and HCl react together to give MgCl and H2 gas which is released in effervescence concentration increases the rate of reaction because there are more molecules of the acid to react with the magnesium however it does not increase the total volume of hydrogen gas released because there is a limited mass of magnesium which will react. If you are doing a level then try comparing mono and dibasic acids eg, HCl and H2SO4 and H2SO4 should be nearly double as fast because of hydrogen ions, however you need to take surface area of Mg into account.

Katie S [last name deleted for privacy by Editor]
- UK

Results on magnesium reacting with hydrochloric acid in the form of a graph


I am doing my course work on an experiment of magnesium strip with hydrochloric acid and I can't find anyone's previous results from the experiment in the form of a graph, could you please send me some past results of the experiment in the form of a graph?

Jon B [last name deleted for privacy by Editor]
- London, England

simultaneous replies 2002
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A. Give in order to get, Jon. E-mail your graph to for posting here, Jon, and then we'll be happy to help others get theirs to you. Or tell us your data and we can help you graph it.

But you should always "lock in" what you found from your own experiment before you consider the results that others got. If you don't do that, you quickly find yourself engaging in 'junk science' (conducting the experiment repeatedly, dismissing unfavorable results as errors, and making whatever wacky adjustments are needed to make it come out the popular way -- the way society dictates instead of the way science dictates).

Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

? A graph of what vs what? Weights, volumes, temperatures, fires, explosions, injured students or ?

James Watts
- Navarre, Florida

A. You could plot a concentration against time graph then find the half lives or if you're using the 'initial rate' method then you could just plot rate or 1/time against concentration and look at the gradient of the graph.

Nikesh Solanki
- London, UK

"A-level" acid reaction experiment generates far more gas than it should

Q. Hi there,

I am currently investigating the order of reaction with respect to reactions with monobasic and dibasic acids for my A-level investigation. I am going to react magnesium with HCl (a monobasic acid) and then H2SO4 (a dibasic acid), and measure every 10 seconds the volume of hydrogen gas produced. I intend to obtain 100 cm3 of gas, and have calculated the volume of acid to use and magnesium mass in the following way:

2HCl + Mg = MgCl2 + H2

number of moles (H2) = (100/1000) dm3 / 24 dm3 = 0.00417 moles Therefore if I want to use 20 cm3 of acid, concentration of HCl = number of moles / volume = 0.00833 / (20/1000) dm3 = 0.417 M Therefore volume of HCl used will be just over 4 cm3 and 16 cm3 distilled water will be used to make a 20 cm3 volume of 0.417 M if the 4 cm3 acid comes from a 2 M bottle of HCl Mass of Mg = 0.00417 x 24 = 0.1 g

Now I have been using 0.2 g so that it is an excess of magnesium, but am producing much much more than 100 cm3 of gas. Could you please explain if any of my calculations are wrong or if I ought to be using an excess of acid rather than magnesium (My intention with the results is to do a graph of Vfinal - Vtime against time, where vfinal - vtime should be proportional to the concentration of acid).

John R. [last name deleted for privacy by Editor]
student - Sheffield, Yorkshire, England

? Have you considered the effect of pressure and temperature on gas volume?

James Totter
James Totter, CEF
- Tallahassee, Florida

A. Okay, I'm in the same position, but from reading your introduction, you want to have the acid in excess, so that its concentration is not changed in the reaction (unless your going to a large amount of decimal places). the magnesium is a solid and can have no concentration change and therefore can have no order.

If you still have the option between mono and di or weak and strong acids, chose weak and strong, it is much much easier as we have more knowledge on how they work.

The results will be that the HCl is order 2 and H2SO4 will be order 1, with HCl having a much quicker rate (get the rate but timing how long it takes for a certain amount of gas to be given off, instead of a total amount produced.

If you have done mono and di like me, then for the theory knowledge of the acids mechanisms is needed in their reaction. I was told that the H2SO4 loses its first h+ faster as it is larger and more unstable, but it means that the second one is much harder to lose, but as I said, the mechanisms need to be analysed to get results. Anyone else reading this some help would be so appreciated,

Tom Clynes
- Chalfont St. Giles, Bucks, UK

thumbs up sign We have additional dialogs on this subject including thread 9644 and 11194.


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey
April 2018

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