[1] Acidic oxides will typically have a low pKa and may be inorganic or organic.
[2] The acidity of an oxide can be reasonably assumed by its accompanying constituents.
Sulfur and nitrogen oxides are considered air pollutants as they react with atmospheric water vapour to produce acid rain.
This property is a key reason for keeping alkali chemicals well sealed from the atmosphere, as long-term exposure to carbon dioxide in the air can degrade the material.
For example, with base different aluminate salts will be formed: Silicon dioxide is an acidic oxide.