How can the total energy of an open system be changed?

According to the tide table below what time of day will the highest tide occur? (2 pt) the highest tide will occur at

The size (radius) of an oxygen molecule is about 2.0 ×10−10m. make a rough estimate of the pressure at which the finite volume of the molecules should cause noticeable deviations from ideal-gas behavior at ordinary temperatures (t= 300k ). assume that deviatons would be noticeable when volume of the gas per molecule equals the volume of the molecule itself.

How many formula units in 2.63 mols of nacl?