Question

Name the following:
Salt used in the laboratory to prepare nitric acid.

Answer 1

• The temperature is controlled below $200°\mathrm{C}$ during the synthesis of nitric acid from sodium or potassium nitrate.
• At higher temperatures, i.e. above $200°\mathrm{C}$, the glass apparatus may be destroyed, and a hard crust of sodium sulphate or potassium sulphate clings to the glass apparatus, making removal difficult.
  ${\mathrm{KNO}}_3\left(\mathrm{aq}\right)+{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\left(\mathrm{conc}.\right)\stackrel{\mathrm{Below}200°\mathrm{C}}{\to }{\mathrm{KHSO}}_4\left(\mathrm{aq}\right)+{\mathrm{HNO}}_3\left(\mathrm{aq}\right)$
  ${\mathrm{NaNO}}_3\left(\mathrm{aq}\right)+{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\stackrel{\mathrm{Below}200°\mathrm{C}}{\to }{\mathrm{NaHSO}}_4\left(\mathrm{aq}\right)+{\mathrm{HNO}}_3\left(\mathrm{aq}\right)$
• Hence, nitric acid $\left({\mathrm{HNO}}_3\right)$ can be prepared using sodium nitrate $\left({\mathrm{NaNO}}_3\right)$ or potassium nitrate $\left({\mathrm{KNO}}_3\right)$.