Equivalent weight is a mass of one equivalent of any chemical element. And an equivalent, in turn, call such quantity of this element any enters direct chemical interaction (reaction) with one moths of hydrogen, or forces out one mol of hydrogen from other connections, reacting with them replacements. The name of this quantity – "equivalent" - not for nothing comes from the Greek word "equal". How equivalent weight is calculated?

## Instruction

1. This problem is solved elementary, with use of simple calculations. It is necessary to remember the rule only well: for determination of equivalent weight it is necessary to know structure of connection of an element with other element which equivalent is known. This universal rule including and calculations at connections of elements with hydrogen.

2. Consider calculations of equivalent weight on some specific objective. For example, alkaline metal sodium taken in number of two grams entirely reacted with halogen iodine, at the same time 13.04 grams of salt of iodide of sodium were formed. Calculate the equivalent mass of sodium if you know that the equivalent mass of iodine is in round figures equal 127 grams/mol.

3. Decision. First of all, define amount of the iodine which reacted with sodium. For this purpose subtract sodium from salt of iodide of sodium: 13.04 - 2.00 = 11, 04 grams.

4. That is 11.04 grams of iodine are the share of two grams of metal sodium. Respectively, 5.52 grams of iodine will fall on one gram of sodium 11.04/2 =. As you know the approximate equivalent mass of iodine (in round figures it is equal to 127), you will elementary find the equivalent mass of sodium. It becomes as follows: 127*1.00/5.52 = 23 grams/mol.

5. If you needed big accuracy, then it would be necessary to consider that the equivalent mass of iodine is equal not 127, but 126.9 grams/mol. Respectively, the specified equivalent mass of sodium would be slightly less: The 22, 989 gram/mol.