Answer is: 8 grams of NaOH.
V(NaOH) = 1 L.
c(NaOH) = 0,1 mol/L.
n(NaOH) = V(NaOH) · c(NaOH).
n(NaOH) = 1 L · 0,1 mol/L.
n(NaOH) = 0,1 mol.
m(NaOH) = n(NaOH) · M(NaOH).
m(NaOH) = 0,1 mol · 40 g/mol.
m(NaOH) = 4 g, pure NaOH.
m(NaOH-50%) = 4 g ÷ 0,5 = 8 g.
n - amount of substance.
c - concentration.
V - volume.
