The weight loss of an aluminum (Al) alloy corroding in HCI acid was observed to be 0.250 g/cm2 after an 8 h immersion period. What is the corresponding corrosion current density in mA/em2, assuming that all the corrosion is due to the reaction: Al → Al3+ + 3e
The atomic weight of Al is 26.98 g/mol.

I = 0.0931 A/cm^2 or 93.1 mA/cm^2

Explanation:

The computation of the corresponding corrosion is shown below:

As we know that

The mathematical form  is

where,

m =  substance mass

Q= total electric charge

F= Faradays constant i.e. = 96,500 C/mol

M = Substance molar mass

z = number of electrons transferred

Now  

Q = It

where

I = current

And t = time

So,

Now it is mentioned that

z=3, M=26.98 g/mol, m=0.25 g/cm2

So,

Hence,

I = 0.0931 A/cm^2 or 93.1 mA/cm^2

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.