A solution of \(\mathrm{NaCl}\) is 1 \(\mathrm{M.}\) Why is the concentration of particles 2 \(\mathrm{M} ?\)

Imagine you're preparing a glass of lemonade. The amount of lemon juice in the water determines how strong the flavor will be. This is similar to the concept of concentration in chemistry, where the focus is on how much solute (like lemon juice) exists within a solvent (like water), in the context of solutions.
Molarity, denoted by the letter M, is a unit that expresses concentration. Specifically, it tells us how many moles of a substance are present in one liter of solution. In the classroom problem, a 1 M solution of NaCl means you have one mole of NaCl in one liter of the mixture. Understanding the concentration of a solution is essential because it can influence the outcome of chemical reactions, the properties of the solution, and its overall behavior.
To clarify, consider that a higher molarity indicates a more concentrated solution. If recipes talk about strong or weak lemonade, in chemistry, we talk about high or low molarity. Importantly, the molarity doesn't factor in how ions break apart in the solution, which transitions us to the topic of dissociation of ionic compounds.

In the realm of chemistry, compounds are like teams where elements combine to achieve stability. Among them, ionic compounds stand out as they are formed by the electrostatic force between positively and negatively charged ions.
Salt, or sodium chloride (NaCl), is the star of our exercise and a prime example of an ionic compound. When it enters water, it doesn't just float around as pieces of NaCl. Each NaCl team splits up, or dissociates, into a sodium ion (Na+) and a chloride ion (Cl-), both of which go their separate ways. It's like when you mix players from different teams, they start to interact in new ways. This dissociation is crucial because it doubles the number of individual entities we have in a solution from what we'd expect if they stayed together as NaCl molecules.
The concept of dissociation is key, especially in how we consider concentration. When measuring the concentration of NaCl, one must account for both the sodium and chloride ions released into the solution. Understanding dissociation helps us realize that molarity is not just about the compound we dissolve but also about the individual ions that result from it.

If you're baking, you likely know the importance of measuring your ingredients correctly. In chemistry, we use stoichiometry in solutions to precisely measure and understand the relations between the amounts of reactants and products in a chemical reaction.
This concept applies to our example of the NaCl solution. The stoichiometry of the dissociation reaction of NaCl tells us that for every one NaCl formula unit that dissolves, we get one Na+ ion and one Cl- ion. So, there's a 1:1:1 relationship or ratio among NaCl, Na+, and Cl-. Just like a recipe would direct you to use one scoop of sugar for one glass of lemonade to maintain that perfect sweet taste.
Application of stoichiometry involves understanding reactions at the mole level. It involves calculations, conversions, and a clear comprehension of molecular interactions. With NaCl dissociating into two types of particles, stoichiometry helps us tally up the complete concentration of all particles, leading to the 2M particle concentration as seen in our problem. This counting of the final total of particles, or ions in the case of dissolved NaCl, is at the heart of chemical solution stoichiometry.