a) nNaOH= 6/40=0,15(mol)
nFeCl3=32,5/162,5= 0,2(mol)
PTHH: 3 NaOH + FeCl3 -> Fe(OH)3 + 3 NaCl
0,15________0,05____0,05________0,15(mol)
Ta có: 0,2/1 > 0,15/3
=> NaOH hết, FeCl3 dư
=> nFeCl3(dư)= 0,2-0,05=0,15(mol)
=> mFeCl3= 162,5.0,15=24,375(g)
b)m(kết tủa)= mFe(OH)3= 0,05.107= 5,35(g)