Question

Acid rain is primarily caused by the emission of which two gases into the atmosphere?

• A. Nitrogen oxides and sulfur dioxide
• B. Carbon monoxide and methane
• C. Ozone and carbon monoxide
• D. Hydrogen sulfide and ammonia

Hint:

• Acid rain is mainly caused by sulfur dioxide (SO$_2$) and nitrogen oxides (NO$_x$). % Corrected
• These gases are released from burning fossil fuels and other industrial/natural processes.
• In the atmosphere, SO$_2$ converts to sulfuric acid (H$_2$SO$_4$). % Corrected
• NO$_x$ converts to nitric acid (HNO$_3$). % Corrected
• These acids lower the pH of precipitation.

Answer 1

The Correct Option is A

Acid rain is a form of precipitation that is unusually acidic, meaning it has elevated levels of hydrogen ions (low pH). It is primarily caused by atmospheric pollution from certain gases that react with water, oxygen, and other chemicals to form various acidic compounds. The two main precursors are: Option (A) Sulfur Dioxide (SO$_2$): % Corrected to SO$_2$

Option (B) Sources: Primarily from the burning of fossil fuels (especially coal) in power plants and industrial facilities, as well as from volcanic eruptions. Option (C) Reactions: SO$_2$ reacts in the atmosphere to form sulfur trioxide (SO$_3$), which then dissolves in water to form sulfuric acid (H$_2$SO$_4$). % Corrected $2\text{SO}_2\text{(g)} + \text{O}_2\text{(g)} \rightarrow 2\text{SO}_3\text{(g)}$ % Assuming \text{} is desired for (g), (l), (aq) $\text{SO}_3\text{(g)} + \text{H}_2\text{O(l)} \rightarrow \text{H}_2\text{SO}_4\text{(aq)}$ % Corrected

Option (D) Nitrogen Oxides (NO$_x$): This term primarily refers to nitric oxide (NO) and nitrogen dioxide (NO$_2$). % Corrected

Option (E) Sources: Primarily from high-temperature combustion processes, such as in vehicle engines and power plants, as well as from natural sources like lightning. Option (F) Reactions: NO$_x$ reacts in the atmosphere to form nitric acid (HNO$_3$) and nitrous acid (HNO$_2$). % Corrected $2\text{NO}_2\text{(g)} + \text{H}_2\text{O(l)} \rightarrow \text{HNO}_3\text{(aq)} + \text{HNO}_2\text{(aq)}$ (simplified) % Corrected Or, NO is oxidized to NO$_2$, then NO$_2$ reacts with hydroxyl radicals or water. % Corrected

Sulfuric acid and nitric acid are strong acids that, when dissolved in atmospheric water droplets, lower the pH of rain, snow, fog, or dry deposition. Options (b), (c), and (d) list gases that are air pollutants but are not the primary precursors of acid rain:

• Carbon monoxide (CO) is a toxic gas but does not form strong acids.
• Methane (CH$_4$) is a greenhouse gas. % Corrected
• Ozone (O$_3$) is a component of smog and a greenhouse gas. % Corrected
• Hydrogen sulfide (H$_2$S) can be oxidized to SO$_2$ and then contribute, but SO$_2$ itself is the major direct precursor. % Corrected
• Ammonia (NH$_3$) is a base and can neutralize acids in the atmosphere, forming ammonium salts. % Corrected

% Using \text{} inside \boxed{} for better line breaking if needed, or a parbox for very long ones. \[ \boxed{\text{Nitrogen oxides and sulfur dioxide}} \]