You think probable to a concentration (and this is expressed in mol/L, g/L etc.).
Brackets around a number mean that the number is of a negative value. Instead of saying -$40 you would express it as ($40).
It is not clear what you mean with "units of power".
It means express the slope along with its measurement units.
You use linear units to express it, such as meters or millimeters, if that's what you mean.
NaCl is sodium chloride.
NaCl has not 2 in the formula unit.
NaCl is the formula for Sodium Chloride - salt.
The text in the brackets must be a question.
I'm going to assume that you mean 23.34g of NaCl. 1 mole NaCl = 58.442g NaCl (the atomic weight of Na and Cl in grams) 23.34g NaCl x (1mol NaCl/58.442g NaCl) = 0.3994mol NaCl
It could be the definition of equivalent ratios.
These are square brackets [ ]
to put into brackets