How many moles and grams of NaOH are needed to dissolve in water to make 4 liters of a 2.0M solution?

The answers are 8.0 moles and 320 grams.

Solution:

Since we are given the concentration of the solution expressed in molarity and the volume of solution, we can use the equation for molarity defined as the number of moles of solute divided by the volume of the solution in liters:

molarity = moles of solute / volume of solution in liters

We rearrange the expression to solve for the number of moles of the solute:

moles of solute = molarity * volume of solution in liters

Substituting the given values, we have

moles of NaOH = (2.0 mol / 1L) * 4L = 8.0 mol

To calculate for the mass of NaOH solute, we will use the molar mass of NaOH that is equal to 40.0 g/mol:

mass of NaOH = 8.0 mol * (40.0g / 1mol) = 320 grams