Maximum percentage of available chlorine on the basis of \(\mathrm{CaOCl}_{2} . \mathrm{H}_{2} \mathrm{O}\) formula is: (a) 40 (b) 35 (c) 49 (d) 45

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the reactants and products in chemical reactions. It is essentially the calculations around converting moles from one substance to moles of another, based on the balanced chemical equation. Understanding stoichiometry is crucial because it ensures that the equations are balanced in terms of both mass and charge. For example, knowing the stoichiometry of a chemical compound such as calcium oxychloride, CaOCl2⋅H2O, can inform us of how much chlorine we can 'access' or utilize from the compound, which is particularly important in applications such as disinfection.

To solve problems involving stoichiometry, you begin by balancing the chemical equation, then convert quantities of known substances into moles using their molar masses before applying the mole ratio from the balanced equation to find the amount of the desired substance.

The molar mass of a substance is the mass of one mole of its particles (atoms, molecules, ions, etc.) and is expressed in grams per mole (g/mol). Calculating molar mass is a fundamental step in stoichiometric calculations as it directly relates mass to the number of moles. To calculate the molar mass of a compound, like CaOCl2⋅H2O, you simply sum the atomic masses of all the atoms present in one molecule of that compound. Here's a simplified visual breakdown:

• One calcium (Ca): 40.08 g/mol
• One oxygen (O): 16.00 g/mol
• Two chlorines (Cl), each 35.45 g/mol, thus 70.90 g/mol for both
• Two hydrogens (H) and one oxygen (O) in the water molecule, comprising 18.016 g/mol

Adding these amounts gives you the total molar mass of the compound. For compounds involved in reactions or applications where specific elements are of interest, like the percentage of chlorine available in chlorine-based disinfectants, focus primarily on the molar mass of the element of interest after determining the molar mass of the whole compound.

The chemical composition of a substance defines what elements it contains and in what proportions. Knowing the chemical composition helps to understand the properties, usage, and behavior of the substance in various reactions. For example, calcium oxychloride, CaOCl2⋅H2O, contains calcium, oxygen, chlorine, and hydrogen. The proportion of the chlorine element within the compound determines its 'available chlorine content'—this is the amount of chlorine that can be utilized for its oxidizing power. The percentage calculation ties stoichiometry and molar mass concepts together. By understanding chemical composition, we can deduce the roles different elements play, whether it's in forming compounds, reacting with other substances, or in providing specific functional characteristics to materials and products.

To accurately assess the chemical composition, it's essential to account for all constituents and their proportions. This is pivotal for applications such as calculating available chlorine in disinfectants, where the effectiveness of the product depends on the concentration of active chlorine in the compound.