Question

How many equivalents are in $$0.40$$ mole of $$K^{+}$$?

Answer 1

Hint: Equivalents is a term related to the valency of the atom in ionic form. It calculates the number of ions required to neutralize the ion with opposite charge.

Complete step by step answer:
The equivalent of an ion is a measure of the charge of an ion. It is equal to the product of the moles of an ion and the valency of the particular ion.
$$numberofequivalents=moles\times valency$$
The mole of an ion is the amount of the ion taken in quantity equal to the molar mass of the ion. The valency of an ion is the number of electrons which is released or accepted to attain the nearest noble gas configuration.
In this case the given ion is potassium ion which is a monovalent ion. The monovalent ions are the ones which require the unit oppositely charged ions to neutralize the charge and become neutral. As the potassium ion carries a $$+1$$ charge so it requires a unit $$-1$$ charge to neutralize.
Each mole of potassium cations produces one mole equivalents of the ion in solution. The valency of the potassium ion is given as $$+1$$ and the mole of potassium ion given is $$0.40$$ mole.
Thus using the equation for determining the number of equivalents
$=molesof{K}^{+}\times valencyof{K}^{+}$
$=0.4mole\times 1Eq/mole$
$=0.4Eq.$

Note: The number of equivalents and moles are important for calculation in setting up reactions. The number of equivalents with respect to the reference starting material is used for determining the exact amount of each of the reactants used in a reaction. The moles and equivalent calculation also derives the amount of product formed in a reaction.