n(NaOH) = n(HCl);
C(NaOH)*V(NaOH) = C(HCl)*V(HCl);
C(HCl) = T(HCl) / M(HCl) = 0.003512 / 36.5 = 0.00009622 моль/см3
C(NaOH) = C(HCl)*V(HCl) / V(NaOH) = 0.00009622 * 20 / 21.12 = 0.00009112 моль/см3
T(NaOH) = C(NaOH)*M(NaOH) = 0.00009112 * 40 = 0.003645 г/см3