\(a,n_{H_2SO_4}=0,5\cdot0,2=0,1\left(mol\right)\\ PTHH:H_2SO_4+2NaOH\rightarrow Na_2SO_4+2H_2O\\ \Rightarrow n_{NaOH}=2n_{H_2SO_4}=0,2\left(mol\right)\\ \Rightarrow a=C_{M_{H_2SO_4}}=\dfrac{0,2}{0,2}=1M\\ b,n_{Na_2SO_4}=n_{H_2SO_4}=0,1\left(mol\right)\\ \Rightarrow C_{M_{Na_2SO_4}}=\dfrac{0,1}{0,2+0,2}=0,25M\)