[irischild22]

 im trying to decided which i unit of measurement i shud use for researching the affect the nature of reactants has on the rate of a reaction. im using 9M HCl and zinc strips and my variabe is the metal so the other metal im using is aluminum strips, i cant decide whether i shud use strips of the same mass or with the same number of atoms (or moles i guess?? im not sure im kind of confused) if i use the same mass then wudnt i b changing the nature of the reactants AND the concentration?? is that too many variables or shud i go by atomic mass and convert equal atomic masses to grams even if the mass in grams is different   bc that wud mean different surface areas. maybe iv completely lost u please respond

[jdurg]

I think it would be best if you used identical surface areas on the strips of metal that you use.  If the Zinc has a surface area of 5 cm², then make sure your Aluminum has a surface area of 5 cm² as well.  This way the surface area of the metal will not alter your results.  (As surface area plays a HUGE role in the rate of a reaction).  Now the same surface area of those two different metals will have a different mass, so it's crucial that you get an accurate mass of each metal as well.  Then just run your reactions and get your data.

With the masses of each metal you can determine the number of moles you have.  You'll also have the time it took for the reaction to complete, so you can then report your answer as X-Moles/Minute.  These values will be absolute comparisons and because the surface areas would be the same, it would be a pretty good indication of which one reacts quicker.