a, nNaOH=12/40=0,3 mol
nMgSO4=12/120=0,1 mol
\(\text{MgSO4+2NaOH=Mg(OH)2+Na2SO4}\)
\(\rightarrow\)nMg(OH)2=nMgSO4=0,1 mol
\(\rightarrow\) mMg(OH)2=0,1.58=5,8g
b, CM NaOH dư= 0,1/0,1=1M
CM Na2SO4= 0,1/0,1=1M
c,\(\text{ Mg(OH)2+2HNO3=Mg(NO3)2+2H2O}\)
nMg(OH)2=0,1 mol
\(\rightarrow\) nHNO3=0,2 mol
\(\rightarrow\) mdd HNO3 25,2%= 0,2.63.100:25,2=50g
\(\rightarrow\) V HNO3=50:1,25=40 ml