Q1: Color of nitric acid is light yellow due to the presence of

ANS:B - NO₂

Nitrogen dioxide (NO2) is a reddish-brown gas at room temperature with a pungent odor. It is a nitrogen oxide and a significant air pollutant, primarily emitted from combustion processes such as vehicle engines and power plants. In the context of nitric acid (HNO3), nitrogen dioxide is dissolved in the solution, contributing to the characteristic yellowish or reddish-brown color of the acid. When nitric acid is exposed to air, it can absorb nitrogen dioxide, forming what's known as "red fuming nitric acid" due to the dissolved nitrogen dioxide. This coloration can vary depending on the concentration of nitrogen dioxide and other impurities present. Nitrogen dioxide itself is a toxic gas and a component of smog. Exposure to high levels of nitrogen dioxide can cause respiratory issues and other health problems. Therefore, controlling emissions of nitrogen oxides like NO2 is important for both environmental and public health reasons.