<h2>The answers are

and

</h2>
Explanation:
Given -
a) The molecular formula of ethylene glycol -

∴ The empirical formula of ethylene glycol will be -

Given -
b) The molecular formula of per-oxo-disulfuric acid (a compound used in bleaching agents) -

∴ The empirical formula of per-oxo-disulfuric acid will be -

Hence, the answers are
and
.
A chemical change changes the bonds by forming or breaking them, and cannot be brought back to it's original form.
b. milk souring
Answer: I think it would be false but im not 1000% sure
Chromium sulfate.
Cr is chromium, and SO4 is sulfate.