9. The solubility of ______ decreases as the temperature is raised. (A) CaO (B) CaCO₃ (C) Ca(OH)₂ (D) NaCl 10. How does stirring affect the solubility of a solid? (A) Increase the pressure (B) Increase the temperature (C) Increases the rate of dissolution of the solute in the solvent (D) Increase the reactivity of the solute and solvent
Answer (1)
The solubility of some substances actually decreases as the temperature increases. Among the given options, calcium carbonate CaCO 3 is such a substance.
For many solids, solubility tends to increase with temperature, but there are exceptions like CaCO 3 , where the opposite is true. This behavior is because the dissolution process of CaCO 3 in water is exothermic, meaning it releases heat. As the temperature rises, this equilibrium shifts to favor the formation of solid CaCO 3 , thus reducing its solubility.
Chosen Option: (B) CaCO 3
Stirring affects the solubility of a solid by increasing the rate at which the solute dissolves in the solvent. While stirring does not change the solubility itself (the maximum amount of solute that can dissolve), it helps disperse dissolved solute particles more quickly throughout the solvent, allowing more solute to come into contact with the solvent at any given time. This enhances the rate of dissolution significantly.
Chosen Option: (C) Increases the rate of dissolution of the solute in the solvent
In summary, temperature and mechanical actions like stirring can both impact the process of how substances dissolve, each in its own way. Temperature can affect the overall solubility depending on the nature of the solute, while stirring primarily accelerates the process of dissolution.
