Answer
0.559 L
Work Step by Step
$M_{1}V_{1}=M_{2}V_{2}$
$\implies M_{2}=\frac{M_{1}V_{1}}{V_{2}}=\frac{5.8\,M\times45.8\,mL}{1000\,mL}$
$=0.26564\,M$
Molarity= $\frac{\text{moles solute}}{\text{liters solution}}=0.26564\,M$
$\implies \text{liters solution}=\frac{\text{moles }\,KNO_{3}}{0.26564\,M}$
$=\frac{\frac{15.0\,g}{101.1\,g/mol}}{0.26564\,M}=0.559\,L$
