All acids, irrespective of their origin, are united by the general property – they contain the hydrogen atoms capable to react. In this regard acids can give the following definition: "Acid is a complex substance in which molecule there are one or several atoms of hydrogen and the acid rest". They are strong and weak. Their force is understood as its ability to give hydrogen ions. If acid easily gives these ions (enters chemical reaction), then it is strong. How it is possible to learn, weak acid, or strong?
Instruction
1. The easiest and evident way (though not really exact) is use of special indicator strips which can be got in shop. It is necessary to apply a drop of acid on such strip and after a while to compare color and intensity of the shown coloring to the samples specified on packing. Than the sample will have brighter, "saturated" red-burgundy color – the acid, and, on the contrary is stronger.
2. If there is no indicator paper or more exact result is necessary, then "the dissociation constant", that is the indicator characterizing ability of substance will come to the rescue (in this case, acids) to break up to ions in water solution. Acids dissociate on a hydrogen cation (proton) and anion of the acid rest. Than this size is higher, that is than ionic disintegration, especially strong acid more proceeds. It is easy to find constants of dissociation of the majority of the known acids in any chemical reference book.
3. It is necessary to consider that for polybasic acids (for example, sulfuric, coal, orthophosphoric and others) which dissociation takes place in several stages, operate with different constants for each stage of dissociation.
4. Force of acid can be determined also how some chemical reactions proceed. For example, if to mix hydrochloric acid with phosphate potassium, chloride potassium and phosphoric acid is formed. If to mix sulfuric acid with carbonic sodium, then sulfate of sodium and coal acid is formed (which is so unstable that will at once break up to water and carbon dioxide). In either case stronger acids (salt and sulfuric) forced out weaker (phosphoric and coal) from their salts. This rule is universal: strong acid always forces out weak of its salt.