Hydrogen reactivity question???

Question

for lab i need to answer the following question: explain why the position of hydrogen cannot be fixed exactly with respect to other metals listed in the reactivity series?

i guess i need to explain why Hydrogen's reactivity cannot be pinpointed exactly........

Answer 1

it can be , & has been positoned.

however in traditional single replacement labs, in which the goal is to establish a reactivity series for metals, we usually use Mg, Zn, Pb, Cu, Ag , & Hydrogen

all of the reaction that we are asked to do react noticably.  

& we find out that

Magnesium is more reactive than Zn

Zinc is more reacive than Lead

Lead is more reactive than copper

and that copper is more reactive than silver

but when we are asked to  position Hydrogen, we find that we have a problem.

that is, though we were able to learn that:

hydrogen is less reactive than Mg & Zn... and that

hydrogen is more reactive than copper & silver

what we realize is that traditionally were we not asked to react it with lead, and so we we don't know whether it is more or less reactive than Lead

had we taken Pb & H2SO4 --> we would have found that it is an extremely slow reaction, but that it does work, showing that Pb is more reactive than Hydrogen

experiments use this omission to test people on single replacement reactions , by asking them what they would chose, in order to test lead vs. hydrogen

well I hope that what I have traditionally seen asked in labs experiments is similar to what you were asked to do