Question

Indicate whether each statement is true or false: (a) If you compare the solubility of a gas in water at two different temperatures, you find the gas is more soluble at the lower temperature. (b) The solubility of most ionic solids in water decreases as the temperature of the solution increases. (c) The solubility of most gases in water decreases as the temperature increases because water is breaking its hydrogen bonding to the gas molecules as the temperature is raised. (d) Some ionic solids become less soluble in water as the temperature is raised.

Short answer

(a) True (b) False (c) False (d) True

Step-by-step solution

Statement (a)

We need to determine if it's true or false that the solubility of a gas in water is more at lower temperature compared to a higher temperature. It is generally true that the solubility of gases in water decreases as the temperature increases. This is because gas molecules have a higher kinetic energy at higher temperatures, making it more difficult for them to be trapped by the water molecules. Thus, statement (a) is true.

Statement (b)

We need to determine if it's true or false that the solubility of most ionic solids in water decreases as the temperature of the solution increases. In general, the solubility of ionic solids in water increases with increasing temperature due to the increased kinetic energy of the water molecules and the increased ability to break the ionic bonds in the solid. However, there are some exceptions where the solubility of ionic solids can decrease with increasing temperature. Thus, statement (b) is false.

Statement (c)

We need to determine if it's true or false that the solubility of most gases in water decreases as the temperature increases because water is breaking its hydrogen bonding to the gas molecules as the temperature is raised. The solubility of most gases in water decreases as the temperature increases, but this is not due to the breaking of hydrogen bonds between water and gas molecules. Rather, it is due to the increased kinetic energy of gas molecules at higher temperatures, making it more difficult for them to be trapped by the water molecules. Thus, statement (c) is false.

Statement (d)

We need to determine if it's true or false that some ionic solids become less soluble in water as the temperature is raised. While it is generally true that the solubility of ionic solids in water increases with increasing temperature, there are exceptions where certain ionic solids become less soluble as temperature increases (e.g., calcium sulfate). So statement (d) is true.

Key concepts

Gas Solubility

Gas solubility refers to the extent to which a gas can dissolve in a liquid, like water. This can be impacted by various factors, with temperature being a key one. When a gas dissolves, its molecules become trapped within the liquid. The general rule of thumb for gases is that they dissolve better at lower temperatures.

- At lower temperatures, gas molecules have lower kinetic energy. - This means they move slower and are more easily captured by liquid molecules. - As temperature increases, gas molecules move faster and tend to escape into the air. Therefore, cooler water can hold more gas because the molecules aren't escaping as quickly. This principle is why beverages are usually carbonated at lower temperatures, ensuring that the fizz, which is essentially dissolved gas, remains in the drink.

Temperature Effects on Solubility

Temperature has a distinct influence on solubility, but the impact differs depending on whether you're dealing with gases or solids. For gases, solubility generally decreases with an increase in temperature.

- Higher temperatures give gas molecules more kinetic energy, encouraging them to escape from the liquid. - Thus, heating a solution often leads to less dissolved gas. However, when it comes to most ionic solids, such as salts, the opposite is often true.

- Typically, solubility increases with temperature for ionic solids. - This happens because increased kinetic energy in the liquid helps break down solid particles, allowing them to dissolve. Despite these general trends, there are exceptions, which students should be aware of. Some ionic compounds, like calcium sulfate, show decreased solubility at higher temperatures.

Ionic Compounds Solubility

Ionic compounds are composed of positively and negatively charged ions bonded together. When these solids dissolve in water, they dissociate into their respective ions. Solubility of ionic compounds can vary significantly depending on temperature.

- In most cases, solubility increases as temperature rises. This is because water molecules, which move faster at higher temperatures, can more effectively disrupt the ionic lattice of the solid. - However, an exception is calcium sulfate, where its solubility decreases at higher temperatures. It’s essential to understand these exceptions because they can affect calculations and experiments in fields like chemistry and environmental science. Knowing which compounds have unusual solubility profiles can also guide practical applications, such as mineral extraction and material use.

Kinetic Energy and Solubility

Kinetic energy is a key player in the solubility of substances. It refers to the energy that particles possess due to their motion.

- At higher temperatures, all molecules, including those of gases and solvents, have more kinetic energy. - For gases, this increase in energy means their molecules are moving too rapidly to stay trapped in the liquid, reducing solubility. In contrast, higher kinetic energy in water molecules at elevated temperatures typically allows ionic solids to dissolve more readily, because: - Water molecules move faster, colliding more effectively with the ionic lattice. - This increased movement helps break the ionic bonds, releasing the ions into the solution. Understanding how kinetic energy affects molecular motion gives insight into why certain solubility trends occur, aiding in the prediction and manipulation of solubility in various conditions.