Some laboratory procedures involving oxygen-sensitive reactants or products call for using preboiled (and then cooled) water. Explain why this is so.

The concept of solubility is foundational to chemistry and pivotal to various scientific processes. Solubility refers to the amount of a substance—solid, liquid, or gas—that can be dissolved in a solvent, such as water, at a specific temperature and pressure. For gases, solubility in water is influenced by temperature; as the temperature increases, the solubility usually decreases. This inverse relationship occurs because higher temperatures energize the water molecules, causing them to move faster and reducing their ability to 'cling' onto the gas molecules.

When discussing gas solubility, it's important to consider Henry's Law, which states that at a constant temperature, the amount of gas that dissolves in a liquid is directly proportional to the partial pressure of that gas above the liquid. This principle explains why carbonated beverages stay fizzier longer when kept chilled and why divers must be cautious of decompression sickness, where decreased pressure can cause gases to come out of solution in the body.

Boiling water is a common laboratory technique with significant effects on the solubility of gases. Boiling occurs when the water temperature reaches a point that allows it to change from a liquid to a vapor. This transition causes the dissolved gases, such as oxygen, to be released from the water. As the water is heated, its molecules move more vigorously, breaking the intermolecular forces that hold them together. They also confront and expel the gas molecules, forming bubbles that rise and release the gas into the atmosphere.

The boiling process is a practical demonstration of how changes in temperature affect the capacity of water to hold gases. It is an application of Le Chatelier's Principle, which predicts how changes in conditions, such as temperature, can shift chemical equilibria—such as the equilibrium between dissolved gas and its gaseous state.

Oxygen-sensitive reactions are an essential consideration in many scientific fields, including chemistry and biology. These reactions can be disrupted by the presence of oxygen, leading to unwanted side effects or entirely different outcomes. For instance, oxygen can cause the oxidation of certain reactants, which might interfere with the reaction or produce undesired products. This is why laboratories sometimes use inert atmospheres or solvents with reduced oxygen content to prevent these unintended occurrences.

In biological contexts, enzymes and cells can also be highly sensitive to oxygen levels, affecting experimental results. Therefore, controlling oxygen concentrations becomes necessary to accurately study aerobic and anaerobic processes in living organisms.

In laboratories, procedures and protocols must be strictly followed to ensure safety, accuracy, and efficiency. The use of preboiled water in handling oxygen-sensitive reactants or products is one such protocol. This is done as a precautionary step to minimize the concentration of dissolved oxygen, which, as we've discussed, can interfere with reactions. After boiling and cooling, the water retains a negligible amount of oxygen because it has not yet re-equilibrated with the atmosphere to regain its original dissolved oxygen content.

For experiments sensitive to oxygen, this reduction in dissolved oxygen allows for more controlled conditions. The practice of using preboiled water exemplifies how an understanding of solubility and boiling can directly impact the procedures used in scientific experimentation. It's a strong reminder of the interconnected nature of scientific concepts and their practical applications in a laboratory setting.