A chemist makes \( 520 . \mathrm{mL} \) of sodium nitrate \( \left(\mathrm{NaNO}_{3}\right) \) working solution by adding distilled water to 90.0 mL of a \( 6.88 \frac{\mathrm{~mol}}{\mathrm{~L}} \) stock solution of sodium nitrate in water.
Calculate the concentration of the chemist's working solution. Be sure your answer has the correct number of significant digits.
\( \square \)
\( \frac{\mathrm{mol}}{\mathrm{L}} \) \( \square \) 100