By studying the reaction it is possible to determine the proton exchange number to determine the normality of the arsenic acid. You probably remember that when a hydrogen atom is ionized and loses its electron, you are left with only a proton. So a hydrogen ion is basically a proton. When H 3 AsO 4 is neutralized by KOH, H 3 AsO 4 provides two protons to form 2H 2 O. Note that H 3 AsO 4 has three hydrogens, but K 2 AsO 4 only has one hydrogen. So, in short, while there is a relationship between the normality of a solution and the molarity of a solution, the normality can only be determined by examining reaction, determining the proton exchange and multiplying molarity by that number.
Normality is particularly useful in titrations calculations.
Percentages can be determined as percent by weight or percent by volume. In order to bring the total quantity to 1 kg, it would be necessary to add 800g water. Solutions based on percent by volume are calculated the same as for percent by weight, except that calculations are based on volume. Search the Web.