Which of the following would you add to a mixture of CaCO3(s) and its saturated solution to increase the molar solubility of CaCO3: more water, Na2CO3, NaOH, NaHSO4? Explain.
Adding more water to a saturated solution will allow more CaCO3 to dissolve due to the now unsaturated mixture.
Adding NaHSO4 adds an acid to CaCO3 and that reacts with CaCO3 and the solubility will be increased.
Can you explain why adding Na2CO3 will DECREASE the solubility CaCO3? Think common ion effect and La Chatelier's Principle.
To determine which substance would increase the molar solubility of CaCO3 in a mixture, it is essential to consider the chemical reactions that occur when each substance is added.
1. More water: Adding more water to the mixture would not increase the molar solubility of CaCO3. Water is the solvent, and increasing the amount of solvent does not affect the solubility of a solute like CaCO3.
2. Na2CO3 (sodium carbonate): Sodium carbonate is a strong base, and in water, it dissociates into sodium ions (Na+) and carbonate ions (CO3²-). When Na2CO3 is added to the mixture, the carbonate ions can react with the dissolved Ca2+ ions from CaCO3 to form insoluble calcium carbonate (CaCO3). This reaction decreases the concentration of Ca2+ ions in the solution, shifting the equilibrium towards increased molar solubility of CaCO3. Therefore, adding Na2CO3 would increase the molar solubility of CaCO3.
3. NaOH (sodium hydroxide): Sodium hydroxide is a strong base, and similar to Na2CO3, it dissociates in water to produce hydroxide ions (OH-). However, NaOH does not provide carbonate ions for the reaction with Ca2+. Hence, NaOH would not increase the molar solubility of CaCO3 significantly.
4. NaHSO4 (sodium bisulfate): Sodium bisulfate dissociates in water to form sulfate ions (SO4²-) and hydrogen ions (H+). The sulfate ions do not provide any significant benefit to enhance the molar solubility of CaCO3. Therefore, NaHSO4 would not increase the molar solubility of CaCO3.
Considering the explanations above, the substance that would increase the molar solubility of CaCO3 in the mixture is Na2CO3 (sodium carbonate).