\(n_{CO_2}=\dfrac{4.48}{22.4}=0.2\left(mol\right)\)
\(n_{NaOH}=0.2\cdot0.5=0.1\left(mol\right)\)
\(T=\dfrac{0.1}{0.2}=0.5< 1\)
\(\Rightarrow CO_2dư\)
\(NaOH+CO_2\rightarrow NaHCO_3\)
\(0.1.............0.1..........0.1\)
\(m_{NaHCO_3}=0.1\cdot84=8.4\left(g\right)\)