Find the weight of \(\mathrm{NaOH}\) in its 60 milli-equivalents.

Equivalent weight is a crucial concept in chemistry that pertains to the mass of a substance that will combine with or displace a fixed amount of another substance. It is often used in reactions involving acids, bases, and salts. To find the equivalent weight, one must divide the molar mass of the compound by its valency.

For example, in the given exercise, sodium hydroxide (NaOH), a base, has a molar mass of approximately 40 g/mol. In a chemical equation, the valency of NaOH is determined by the number of hydroxide ions (OH^-) it can provide, which is one. Hence, its equivalent weight is calculated as 40 g/mol divided by 1, resulting in 40 g/equivalent.

The concept of equivalent weight is applied when dealing with titration and stoichiometric calculations in various chemical reactions. This simplifies the process of understanding how different substances will react in equivalence based on their weights rather than dealing with the number of moles directly.

Valency is a fundamental concept in chemistry that plays a role in determining how atoms bond and react with each other. It refers to the combining capacity of an element, which is the ability of its atoms to bond with a certain number of atoms of another element. Valency is determined by the number of electrons an atom can donate, accept, or share when forming chemical bonds.

In the step-by-step solution for the exercise, NaOH has a valency of 1. This means that each sodium hydroxide molecule can donate one hydroxide ion (OH^-) in reactions. Understanding valency is key to predicting the formulas of the compounds formed in reactions and is vital for balancing chemical equations. For instance, the valency of NaOH is utilized in the calculation of its equivalent weight and is a building block for understanding stoichiometry in chemical reactions.

Stoichiometry involves the calculation of reactants and products in chemical reactions. It is based on the law of conservation of mass, which states that in a chemical reaction, mass is neither created nor destroyed. Stoichiometry takes into account the molar ratios of the reactants and products as shown in the balanced chemical equation.

In practice, stoichiometry is used to calculate the amounts needed or produced in a reaction. The calculation from the exercise uses stoichiometric principles to find the weight of NaOH. By multiplying the equivalent weight of NaOH by the number of equivalents (which in this case are milli-equivalents), we can determine the actual weight of the substance that will react. Stoichiometry is not just about calculations; it is integral in predicting yield, understanding reaction mechanisms, and even in industrial applications for scaling up reactions.