How Does HCl Concentration Affect the Rate of Mg Reaction?

[gsingh2011]

I have to do a lab investigating factors that affect the rate of reaction between Mg(s) and HCl(aq). I decided to change the concentration of HCl. I timed how long it took for the Mg to completely disappear when the HCl was in excess and the amount of Mg used is constant. Obviously the higher the concentration, the lower the time, the faster the rate of reaction. My question is that since I'm using solid Mg, I can't really talk about the concentration of that... so is it simply enough to say that the lower times means that the rate is faster? I can't say rate=Delta[Mg]/Delta(t) if there's no concentration of Mg. I'm just confused on how to correctly explain this without a concentration, what do I do?

 

[gsingh2011]

Nevermind, I figured out the moles of a product using stoich. and then I could find the molarity of that :)

 

[Gokul43201]

Nevertheless, things do get tricky when it comes to defining concentrations (or activities) of solids. For the scope of this lab, I think you would be well-advised to be consistent with your use of Mg ribbons between different runs - make sure they have the same mass and roughly the same surface area.