ms = 800g , c% = 20%
stim ca c% = mdx100/ms
=> md = msxc%/100
= 800x20/100 = 160 g NaOH
160 g md n moli
NaOH + HCl --> NaCl + H2O
40 36,5 1
=> md = 160x36,5/40 = 146 g HCl
=> ms = mdx100/c%
= 146x100/20% = 730 g sol. HCl
ro = ms/Vs
=> Vs = ms/ro = 730/1,1 = 663,64 cm3 sol. HCl
=> n = 160x1/40 = 4 moli NaCl