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Calculates pH of solutions after addition of chemicals (acids, bases, salts) Calculates the calcite-carbonate system (closed/open CO 2 system, Langelier Saturation Index) Calculates mineral dissolution, precipitation, and saturation indices; Calculates mixing of two waters; Calculates reduction-oxidation reactions; Plots titration curves
Diagram depicting the sources and cycles of acid rain precipitation. Freshwater acidification occurs when acidic inputs enter a body of fresh water through the weathering of rocks, invasion of acidifying gas (e.g. carbon dioxide), or by the reduction of acid anions, like sulfate and nitrate within a lake, pond, or reservoir. [1]
Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but acid rain has a pH level lower than this and ranges from 4–5 on average. [1] [2] The more acidic the acid rain is, the lower its pH is. [2] Acid rain can have harmful effects on plants, aquatic animals, and infrastructure.
The reaction quotient (Q r) is the ratio of the chemical activity (a i) of the reduced form (the reductant, a Red) to the activity of the oxidized form (the oxidant, a ox). It is equal to the ratio of their concentrations (C i) only if the system is sufficiently diluted and the activity coefficients (γ i) are close to unity (a i = γ i C i):
Acid-neutralizing capacity or ANC in short is a measure for the overall buffering capacity against acidification of a solution, e.g. surface water or soil water.. ANC is defined as the difference between cations of strong bases and anions of strong acids (see below), or dynamically as the amount of acid needed to change the pH value from the sample's value to a chosen different value. [1]
In the process of oxidizing the organic substances found in the water sample, potassium dichromate is reduced (since in all redox reactions, one reagent is oxidized and the other is reduced), forming Cr 3+. The amount of Cr 3+ is determined after oxidization is complete and is used as an indirect measure of the organic contents of the water sample.
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Upon exposure to oxygen (O 2) and water (H 2 O), metal sulfides undergo oxidation to produce metal-rich acidic effluent. If the pH is low enough to overcome the natural buffering capacity of the surrounding rocks (‘calcium carbonate equivalent’ or ‘acid neutralising capacity’), the surrounding area may become acidic, as well as contaminated with high levels of heavy metals.