Final answer:
The most likely pH of acid rain is 4, as normal rainwater has a pH of 5 to 6, and the most acidic rain recorded had a pH of about 4.3. Acid rain becomes acidic due to sulfur dioxide and nitrogen oxides from fossil fuel emissions.
Step-by-step explanation:
Acid rain is a form of precipitation with a significantly lower pH, which indicates a higher level of acidity. Normal rainwater is slightly acidic with a pH between 5 and 6 due to the presence of dissolved carbon dioxide (CO2) forming carbonic acid. However, when looking at acid rain, which is rainwater with a pH of less than 5, we find that other non-metal oxides like sulfur dioxide (SO2) and nitrogen oxides (NOx) can dissolve in the water to form stronger acids such as sulfuric acid and nitric acid.
Given the historical data, the pH of the most acidic rain recorded in the U.S. is about 4.3. Therefore, the most likely pH of acid rain from the provided options would be B. 4. This acidic precipitation occurs due to the emissions from burning fossil fuels, mainly emitting SO2 and NOx. These compounds react with water in the atmosphere and lower the pH of the precipitation, leading to acid rain.