Explain the equivalent mass of element,acid,base,molecule and salt? Also give the formulae for these.
Equivalent mass of a substance is that mass which is capable of donating/accepting/sharing one mole of electrons.
1) The equivalent mass of an atom = atomic mass/valency of the atom
For example:- Sodium Atom(Na) has an atomic mass of 23 g/mole and a valency of 1
Thus, equivalent mass of Na = 23/1 = 23 g/equivalent
2) The equivalent mass of ion = ionic mass/charge on that ion
For example:- Sodium ion(Na^+1) has an ionic mass of 23 g/mole and a charge of +1
Thus, equivalent mass of Na^+1 = 23/1 = 23 g/equivalent
3) The Equivalent mass of Salt = Molecular mass of salt/(No. of cations/anions*charge on that ion)
For example:- Sodium Sulfate(Na2SO4) has an molecular mass of 142 g/mole and a there are two numbers of cation Na+ each ahving a charge of +1 while there is one anion (SO4)^2- having a charge of -2
Thus, equivalent mass of the salt (using cation) = 142/(2*1) = 71 g/equivalent
equivalent mass of the salt (using anion) = 142/(1*2) = 71 g/equivalent