Respuesta :

n(NaOH) = N(NaOH) / NA = 2.40 × 1022 / 6.02 × 1023 mol-1 = 0.0399 mol.
m(NaOH) = n(NaOH) × M(NaOH) = 0.0399 mol × 40 g/mol = 1.596 g ≈ 1.60 g.
Hope this helps :)

1.39 g

the mass of 2.10×10^23

molar mass 40.0 g/mol