Can you Give me Feedback on My Exam Question

[DrSims]

Hello,
I am teaching for my first time this semester. In writing my exam, I felt pretty good about most of my questions except one.
I was wondering if anyone could provide feedback on their initial assessment of the question. My hope is that the students will use a shortcut to show that at unit activity the corrosion process still moves forward in 0.1M instead of doing a second full calculation.
Any thoughts?

1) Will pure cobalt react with 0.1M HCl? Assume a starting concentration of 1x10-12 Co2+ ions in solution. Is there an activity/concentration of Co2+ ions that will cause the reaction between 0.1MHCl and pure cobalt to stop? (40 points)

 

[bimr]

Don't like the question. I would answer yes/no. There is a chemical reaction. When a chemical reaction goes to completion, that means the reaction will stop. That also implies that all of the initial reactants are used up to form the products. This implies that the concentration of the products is much greater than the concentration of the reactants.