[beartear]

Hello,

If I were to create an investigation of the effects of HCl concentration on the rate of reaction of magnesium. When I increase the concentration of HCl, the rate of reaction should increase, and vice versa. Correct?  Is it possible to calculate the amount of time needed to dissolve the magnesium in different concentrations of HCl? Thanks 

[Fluorine]

If I were to create an investigation of the effects of HCl concentration on the rate of reaction of magnesium. When I increase the concentration of HCl, the rate of reaction should increase, and vice versa. Correct?

Yes, if temperature is the same.

Is it possible to calculate the amount of time needed to dissolve the magnesium in different concentrations of HCl?

Mathematically
If you want to punch out the numbers you can follow a chemical kinetic rate equation if you know the rate constant k or are capable of rearranging to solve for it.



Experimentally

2HCl_(aq) + Mg_(s) MgCl_2(aq) + H_2(g)

If you want to do this experimentally, with chemical equation you can see it goes from an acidic to a neutral solution. So one way is timing the reaction of a certain mass of Mg in a specific concentration of HCl with an indicator.Phenolphthalein would be a good choice, which is a vibrant pink when acidic and becomes clear when neutralized. There are other methods, though I don't know any simpler experimental ones personally.

[beartear]

The reaction produces hydrogen gas. To measure the volumes of hydrogen gas, I would have to use an eudiometer. I was wondering how an eudiometer works. Can someone explain it to me? Thanks 

[Fluorine]

You don't need to calculate the volume of hydrogen produced to know the rate of reaction. It is possible by this method but I'd say it's far less effective because gas escaping can throw out your calculations.

I was wondering how an eudiometer works. Can someone explain it to me?

This image explains it more or less; the hydrogen gas produced displaces the solution in the eudiometer. If you know the initial and final volume of the solution you'll get volume of gas produced. However you should know the pressure and temperature to properly complete your calculations. Simply assuming 1atm and 25 ^oC is not going to give you a reliable answer. From their you could use PV/nT=R to see how well you preformed it.

[beartear]

What would another method be?  
And how would I attach the magnesium to the eudiometer? Would I have to use a wire of some sort? How should I wrap the wire around the magnesium if so? 

[Fluorine]

What would another method be?

I explained already;

Experimentally

2HCl_(aq) + Mg_(s) MgCl_2(aq) + H_2(g)

If you want to do this experimentally, with chemical equation you can see it goes from an acidic to a neutral solution. So one way is timing the reaction of a certain mass of Mg in a specific concentration of HCl with an indicator.Phenolphthalein would be a good choice, which is a vibrant pink when acidic and becomes clear when neutralized. There are other methods, though I don't know any simpler experimental ones personally.

How should I wrap the wire around the magnesium if so?

Get copper wire and wrap the magnesium piece around it. Roll up the magnesium (fairly soft metal) if it's a strip form. Copper, if you check the reactivity series, is below hydrogen meaning it is not reactive enough to displace hydrogen to get with chlorine. However magnesium is more reactive than hydrogen and will react with the acid.

Get a rubber stopper with a small hole in it (see this image) put the caged magnesium on the bottom side and pull a bit of the wire out and back in from the side. When you try closing the stopper it will trap the free end of the copper wire between it and the glass holding the magnesium in place.

Here are some pictures of my Mg/HCl eudiometer lab;

- Cu caged Mg in eudiometer
- Complete set up
- Eudiometer measurements

[beartear]

Should I wrap the whole strip of magnesium around the copper wire? Or should I wrap the magnesium around the copper wire once? I couldn't really tell from the picture because of the flash 

[Fluorine]

Copper cages the magnesium not magnesium caging the copper. The only purpose the copper serves is to prevent the magnesium from falling through the stopper hole. The stopper hole is there to allow gas to displace the solution. If you cover up the stopper hole "you've [potentially] made a bomb", as my professor would always say.

One last time;


1) Roll/curl the magnesium up - if it's been oxidized use sandpaper to clean then weight it.
2) Get a copper wire and twist it around the magnesium to protect it from falling through the stopper hole. Magnesium will be "chewed up", in a respect, by the HCl and start to break apart. If you lose any material it's experimental error.
3) Make a hook coming out and back in from the side of the stopper and then cap it.

This is not a effective method to calculate rate of a reaction due to product/reactant potential loss.

[beartear]

Thank you very much!  
How much I determine the volume of hydrogen gas produced?
I've tried doing this:

V_H2 = L / 1 mol HCl * mol HCl / 36.49g * 24.31g / mol Mg * 1 mol Mg / 1 mol H₂ , but the answer doesn't come out to be in the right units.