Answer:
[tex]\boxed {\boxed {\sf B. \ 0.5 \ M}}[/tex]
Explanation:
Molarity is a measure of concentration in moles per liter. The formula for calculating molarity is:
[tex]molarity= \frac{moles \ of \ solute}{ liters \ of \ solution}[/tex]
There are 2 moles of a compound or the solute. There are 4 liters of water or the solution.
Substitute the values into the formula.
[tex]molarity = \frac{ 2 \ mol}{ 4 \ L}[/tex]
Divide.
[tex]molarity= 0.5 \ mol /L[/tex]
1 mole per liter is equal to 1 Molar, so the solution's molarity of 0.5 mol/L is equal to 0.5 M.
[tex]molarity = 0.5 \ M[/tex]
The molarity of the solution is 0.5 Molar and choice B is correct.