Which of the following correctly states the relationship between temperature and the solubility of a substance in water?
a) The solubility of a substance in water increases as the temperature rises, especially for gases.
b) The solubility of a substance in water decreases as the temperature rises, especially for ionic solids.
c) The solubility of a substance in water with temperature cannot be accurately predicted, especially for ionic solids.
d) The solubility of a substance in water decreases as the temperature lowers, especially for gases.
e) Both A and D are correct.
The correct answer and explanation is :
The correct answer is a) The solubility of a substance in water increases as the temperature rises, especially for gases.
Explanation:
The relationship between temperature and the solubility of a substance in water can vary depending on the type of substance (solid, liquid, or gas). However, in general:
- Solubility of Ionic and Molecular Solids:
For most solid solutes (such as ionic compounds like salts), their solubility in water generally increases as the temperature increases. This is because higher temperatures provide more energy, which helps break the bonds or interactions between the solute particles (such as ionic bonds in salts) and allows the solute to dissolve more readily. For example, many salts like sodium chloride (NaCl) dissolve better in hot water than in cold water. - Solubility of Gases:
For gases, the solubility typically decreases as the temperature rises. This is because as temperature increases, the kinetic energy of the gas molecules also increases, making it harder for them to remain dissolved in the water. The gas molecules tend to escape from the solution to the atmosphere, leading to a decrease in solubility. This is why warm soda (which contains dissolved carbon dioxide) often fizzes more when opened, as the gas escapes more readily due to the higher temperature. Example: Carbon dioxide (CO₂) in carbonated beverages is more soluble in colder water than in warmer water. This is why soda bottles are often kept cool to retain the carbonation. - Specific Cases:
While the general rule is that solubility increases for solids with increasing temperature and decreases for gases, there are exceptions depending on the chemical nature of the solute. Some substances, especially certain salts, may exhibit unusual behavior under extreme conditions.
Thus, answer a) is correct because it reflects the general behavior of solubility for solids and gases in water. Answer d) is incorrect because it focuses only on gases and overlooks the behavior of solids.