Select the correct alternative from the given choices. \(44 \mathrm{~g}\) of \(\mathrm{CO}_{2}\) contains (a) 2 moles of oxygen atoms (b) 1 mole of oxygen atoms (c) \(1.5\) moles of oxygen atoms (d) 2 moles of oxygen molecules

Understanding the molar mass is crucial when dealing with chemical reactions and formulae. The molar mass is defined as the mass of one mole of a given substance (chemical element or chemical compound) expressed in grams per mole (g/mol). It corresponds to the mass of 6.022 x 10²³ (Avogadro's number) of its particles - be they atoms, molecules, ions, or others.

For example, in the exercise, the molar mass of carbon dioxide (CO₂) is calculated by adding the mass of one carbon atom (12.01 g/mol) to the mass of two oxygen atoms (2 x 16.00 g/mol), yielding approximately 44.01 g/mol. This figure is pivotal when converting between the mass of a substance and the equivalent number of moles.

Stoichiometry can be considered the 'accounting' of chemistry. It deals with the quantification of substances involved in chemical reactions based on balanced chemical equations. By using stoichiometry, we can predict how much reactant is needed or product is formed in a given chemical reaction.

The stoichiometric coefficients in a chemical equation give the ratio in which substances react or form. To solve problems using stoichiometry, one must first balance the chemical equation, determine the molar ratio, and then apply these ratios to find the desired quantity. In the exercise, the stoichiometry of the reaction tells us that for every mole of CO₂, there are exactly two moles of oxygen atoms.

The chemical composition of a substance provides information about the elements present and their relative proportions. Knowing the chemical composition is vital for understanding the properties and behavior of the substance.

For CO₂, its chemical composition is made of one carbon atom and two oxygen atoms. The mass ratio of these atoms defines its composition and determines physical properties such as density and molecular weight. Accurately calculating the composition can also help in identifying substances and predicting their reactivity.

Avogadro's number, an essential constant in chemistry, is defined as the number of constituent particles (usually atoms or molecules) found in one mole of a substance. Its value is approximately 6.022 x 10²³ entities per mole.

This large number allows chemists to use the mole as a bridge between the microscopic world of atoms and molecules and the macroscopic world we experience. In mass and number of moles calculations - as seen in the exercise with CO₂ - Avogadro's number helps us understand that a mole of any substance contains the same number of particles as a mole of any other substance.