Answer: The moles of substance present is 0.1 mol and molarity of the solution is 0.4 M.
Explanation:
Given: Mass = 4 g
Volume = 250 [tex]cm^{3}[/tex] (1 [tex]cm^{3}[/tex] = 0.001 L) = 0.250 L
Moles is the mass of a substance divided by its molar mass.
So, moles of NaOH (molar mass = 40 g/mol) is calculated as follows.
[tex]Moles = \frac{mass}{molar mass}\\= \frac{4 g}{40 g/ml}\\= 0.1 mol[/tex]
Molarity is the number of moles of a substance present in liter of a solution.
Hence, molarity of given NaOH solution is as follows.
[tex]Molarity = \frac{moles}{Volume (in L)}\\= \frac{0.1 mol}{0.250 L}\\= 0.4 M[/tex]
Thus, we can conclude that moles of substance present is 0.1 mol and molarity of the solution is 0.4 M.
