Hey there!
For SN1 mechanism; the activation barrier is the C-I bond energy which is broken in the first step of the reaction.
The activation barrier is : 56 kcal/ mol = 5.6 kcal/ mole ( nearest 0.1)
Yes. A mixture can be made up of just elements without the use of a compound, you can also just use compounds in a mixture without any elements
D. Dependent on an objects position
I think it would be:
Is the author stating fact or opinion?
Does the author have evidence for the given facts?
Maybe
How many article has the author written before?
Ones you add if you wanted to is
Does the author give any sources? (Like where they got the info)
