why is unpolluted rain acidic?
824709
even if the air isnt polluted, there is still carbon dioxide and water vapor in the air.  When carbon dioxide(CO2) and water(H2O) react in air, they form Carbonic Acid (H2CO3).  Since it is an acid, it is acidic
311001
It does, tho not necessarily rain that's made of water. It could be acid rain or something like that.
841635
The process that leads to acid rain begins with the burning of fossil fuels. Burning, or combustion, is a chemical reaction in which oxygen from the air combines with carbon, nitrogen, sulfur, and other elements in the substance being burned. The new compounds formed are gases called oxides. When sulfur and nitrogen are present in the fuel, their reaction with oxygen yields sulfur dioxide and various nitrogen oxide compounds. In the United States, 70 percent of sulfur dioxide pollution comes from power plants, especially those that burn coal. In Canada, industrial activities, including oil refining and metal smelting, account for 61 percent of sulfur dioxide pollution. Nitrogen oxides enter the atmosphere from many sources, with motor vehicles emitting the largest share—43 percent in the United States and 60 percent in Canada.\n\nOnce in the atmosphere, sulfur dioxide and nitrogen oxides undergo complex reactions with water vapor and other chemicals to yield sulfuric acid, nitric acid, and other pollutants called nitrates and sulfates. The acid compounds are carried by air currents and the wind, sometimes over long distances. When clouds or fog form in acid-laden air, they too are acidic, and so is the rain or snow that falls from them. \n\nAcid pollutants also occur as dry particles and as gases, which may reach the ground without the help of water. When these “dry” acids are washed from ground surfaces by rain, they add to the acids in the rain itself to produce a still more corrosive solution. The combination of acid rain and dry acids is known as acid deposition.\n\nKKG
509217
Mostly water (!), dissolved atmospheric gases, including CO2 which makes it slightly acidic, NOx and SOx compounds which also make it acidic and particulates. The significance of the dissolved and particulate compounds cannot be underestimated in this day and age, for example it is now true that the majority of pollutants enter Lake Superior (which, granted, has a small, forested watershed) through atmospheric deposition rather than inflow off the watershed.
704222
rain water is mildly acidic (carbonic acid) and so will dissolve minerals found in rock.  For example, if you look at an old building made from limestone the corners will be slightly round and the surface will be pitted.  This is because limestone is made from calcium carbonate which is easily dissolved by acids.\nThis is also the same effect which produces limstone caves and why the surface of rocks appear discoloured and weathered.
318259
soil pH typically varies on a much smaller scale than country or climate zone.  Here in the Blue Ridge Mountains, some valleys have acid soil ("sour" to the old-school farmers who didn't have a meter fancier than their tongue) while over the next hill it may be "sweet," that is, neutral to basic.  Here it depends on the kind of rock under the soil.
701551
No. It is a chemical compound. All rain water is a compound of two elements hydrogen and oxygen. The chemical formula for water is h2o - meaning two hydrogen atoms and one oxygen. Usually when rain becomes acid it has sulfur dioxide (another compound formed of sulfur and oxygen) and nitrogen oxide (yet another compound formed from the combination of the elements nitrogen and oxygen as well). These chemicals combine with the water to form sulphuric acid and nitric acid.
293854
Rain forces down cooler air from the atmosphere.
474398
HOW ACID RAIN IS FORMED\n\nAcid rain is caused by the release of the gases SO2 (sulphur dioxide) and NOX (nitrous oxides). The main sources of SO2 in South Africa are coal-fired power stations and metal working industries. The main sources of NOX emissions are vehicles and fuel combustion.\n\nSulphur dioxide reacts with water vapour and sunlight to form sulphuric acid. Likewise NOX form nitric acid in the air. These reactions takes hours, or even days, during which polluted air may move hundreds of kilometres. Thus acid rain can fall far from the source of pollution. \n\nWhen mist or fog droplets condense they will remove pollutants from the air and can become more strongly acid than acid rain. Even snow can be acid. Gases and particles, not dissolved in water, with a low pH can also be deposited directly onto soil, grass and leaves. It is possible that even more acidity is deposited in this way than by rain! Not much is known about this process, and it is particularly difficult to study.\n\nhttp://www.botany.uwc.ac.za/Envfacts/facts/acidrain.htm\n\nhttp://www.botany.uwc.ac.za/Envfacts/facts/acidrain.htm
439975
Acid rain is caused by the combustion of fossil fuels, primarily the burning of coal but gasoline combustion also contributes. Burning of fossil fuels produces nitrogen oxide and sulfur dioxide which after emission transform into Sulfate and nitrate particles which combine in the air to form sulfuric and nitric acids. These acids fall to the earth as rain or other precipitation and get deposited in lakes and rivers and soil. \nA short term solution to problems associated with acid rain is to add a buffer to lakes other water sources to neutralize the acid but this is an expensive and temporary solution. The best way to prevent acid rain is to reduce emissions of the harmful substances by reducing the combustion of fossil fuels and practicing energy conservation or using other cleaner energy sources, like wind or solar power.
527182
The pH of acid rain can be anything less than the pH of normal rain, which actually tends to be around 5-6 (rather than 7 as you might expect).  There's no magic pH at which it becomes acid rain; it just depends on how much acid is around.  Sometimes the pH can be as low as 2, or even 1, other times it will be more like 3 or 4, it really just depends how much pollution there is.  If you want us to find the concentration of H+ in the acid rain, you have to tell us what pH you're thinking of!\n\nAs for the coffee thing, you should be able to figure that out yourself for any given pH using the formula pH = -log[H+] and solving for [H+].
547960
The water is in the form of a vapor or gas, like steam.  When the vapor becomes concentrated enough to form droplets, it turns to rain.
159953
When moist air cools (air collects moisture through evaporation) that moisture starts to condense (think the side of your can of pop in the summer with all the droplets on it).  That's what clouds are, condensation.  Back to the pop can, when too much moisture collects on the side, it starts to run down the can.  That's what happens in the cloud -- too much moisture causes precipitation (rain).
295876
See the reference below for a more complete description.\n\nHowever, consider a factory which emits sulfur dioxide\nwhich then mixes with water in the air:\n\nS02 + H20 ==> H2SO3      (the numbers should be subscripts)\n\nMy understanding is that with one more interaction with\nwater, it creates sulfuric acid and hydrogen:\n\nH2S03 + H20 ==> H2SO4 + H2\n\nThus, you have acid in the air which is carried down\nwith rain to be acid rain.
925984
YES, EG. SALIVA FOR EXAMPLE IS MORE BASIC THAN ACIDIC, AS IS ALSO  HUMAN BLOOD. THE Ph OF BLOOD IS 7.62,  NEUTRAL Ph IS 7.0.
467833
In some countries, they spray the top of the clouds ("seed the clouds") with chemicals (AgI or AgCl).  This causes the small water droplets in the cloud to grow, and finally the drops are big and heavy enough to fall to the ground in the form of rain.\n\nThe reason for doing this could be that you really don't want rain in a certain area, and you think it is a better idea to make the potential rain clouds "release the rain" in another area, before they have moved with the wind to the area you want to protect.\n\nSo, the rain is not really artificial, but the cause of the rain is artificial.
211023
wow, well put mrjeffy! I have one thing to add though. Because all acids and bases are electrolytes, you can use pH to determine what is and isn't an electrolyte in a solution. If it come out as acidic or basic, it is and electrolyte(the darker, the more basic or acidic). If it comes out neutral, like Distilled Water, it is not. Also don't forget that non-electrolytes will not completely dissolve into solution in water.