2.5 moles of sodium chloride is dissolved to make 0.050 liters of solution

The answer is:

the molarity = 50 moles/liters

The explanation:

when the molarity is = the number of moles / volume per liters.

and when the number of moles =2.5 moles

and the volume per liters = 0.05 L

so by substitution:

the molarity = 2.5moles/0.05L

                    = 50 moles /L

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)

i don,t know so just answer mine