Answer: Because the acre is a measure of area, it has no definite perimeter. For example, using the examples in question one, the perimeter of the long, skinny sidewalk acre would be 17,434 feet (more than 3 miles), but the perimeter of the square acre would be 835 feet.
No other molecular fluoride of krypton has been isolated, so all krypton compounds are derived from KrF 2, where Kr is in the +2 oxidation state. Krypton difluoride is a powerful oxidative fluorinating agent. (Its oxidizing power means that it extracts electrons from other substances and confers on them a positive charge.
In Post Crisis continuity, Kryptonite only affects Kryptonians that originate from the same reality. Superman once visited a Pocket Universe wherein he discovered that three Kryptonian conquerors had devastated the Earth, ultimately conquering it. Superman used gold Kryptonite to remove their powers.