Question

The mass of NaOH present in 40.0 mL of a 2.0 M NaOH solution is

Answer 1

Molarity = number of moles of solute present in 1L of the solution.

Molarity = no. moles/ volume in L
  
no. moles = mass of solute / Mol. weight of solute

therefore,

Molarity M = (mass of solute / mol.wt of solute)x(1/volume in Liters)

Given, Molarity M = 2.0 M ; volume = 40 mL = 0.04 L
NaOH mol. weitght = 40 g/mol

plugging these values in Molarity;

2.0 = (mass of NaOH/40 g/mol)x (1/0.04 L)

mass of NaOH = 3.2 g

Therefore, the mass of NaOH present in 40mL of a 2M NaOH solution is 3.2 g