Calculate the molarity of each solution. (a) \(33.2 \mathrm{~g}\) of \(\mathrm{KCl}\) in \(0.895 \mathrm{~L}\) of solution (b) \(61.3 \mathrm{~g}\) of \(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}\) in \(3.4 \mathrm{~L}\) of solution (c) \(38.2 \mathrm{mg}\) of \(\mathrm{KI}\) in \(112 \mathrm{~mL}\) of solution

Molar mass is a fundamental concept in chemistry that represents the mass of one mole of a given substance. It is typically expressed in units of grams per mole (g/mol). To calculate the molar mass of a compound, you sum the atomic masses of each element present in the compound, multiplied by the number of atoms of that element in the molecular formula. For instance, in one molecule of potassium chloride (KCl), there is one atom of potassium (K) and one atom of chlorine (Cl). Using the atomic masses from the periodic table, potassium has an approximate atomic mass of 39.1 g/mol and chlorine has an atomic mass of 35.5 g/mol. Therefore, the molar mass of KCl is calculated by adding these two atomic masses, resulting in 74.6 g/mol.
The ability to calculate molar mass is essential when converting between the mass of a substance and the number of moles. When faced with an exercise requiring molar mass, always start by identifying the chemical formula of the substance and then use the periodic table to find the atomic masses of each element. With practice, determining molar mass becomes a straightforward task that is the first step in many stoichiometric calculations, including molarity.

The mole is a basic unit in chemistry that provides a bridge between the atomic world and the macroscopic world we live in. One mole corresponds to Avogadro's number, which is approximately 6.022 x 10²³ particles - atoms, molecules, ions, or electrons. The moles of a compound represent the amount of substance containing this many discrete particles.

To calculate the number of moles from the mass of a compound, you divide the given mass by the molar mass of the compound. For example, if you have 33.2 grams of KCl, and you know from the calculation of molar mass that one mole of KCl weighs 74.6 grams, then you can calculate the moles of KCl by dividing the mass of the potassium chloride (33.2 g) by the molar mass (74.6 g/mol), which gives you approximately 0.445 moles. Understanding the concept of moles is crucial because it allows you to count particles by weighing them, which is necessary for quantifying reactions and concentrations in solutions.

Solution concentration is a measure of how much solute is dissolved in a given volume of solvent. Common units for expressing concentration include molarity (M), which is moles of solute per liter of solution. Molarity is a commonly used concentration unit because it directly relates to the number of moles of a solute in a specific volume, making it valuable for reaction stoichiometry in solutions.

To calculate molarity, divide the number of moles of the solute by the volume of the solution in liters. For example, if you dissolved 1.330 moles of ethanol (C2H6O) in 3.4 liters of water, the molarity would be calculated as 1.330 moles divided by 3.4 liters, yielding a molarity of 0.391 M. When performing molarity calculations, be sure to pay attention to units, converting mass to moles, and volume to liters if necessary. This standardized approach simplifies the comparison of concentrations across different solutions. Through understanding molar mass, moles, and solution concentration, students can grasp the fundamental aspects of solution chemistry vital for laboratory work and detailed analysis of reactions.