m(AlCl3)=25 г
Найти m(Naoh)
AlCl3+NaOH=....

дано

m(AlCL3) = 25 g

------------------------

m(NaOH)-?

AlCL3+3NaOH-->Al(OH)3+3NaCL

M(AlCL3) = 133.5 g/mol

n(AlCL3) = m/M = 25 / 133.5 = 0.19 mol

n(AlCl3) = 3n(NaOH)

n(NaOH) = 3*0.19 = 0.57 mol

M(NaOH) = 40 g/mol

m(NaOH) = n*M= 0.57 * 40 = 22.8 g

ответ 22.8 г