How many grams of solid K2CO3 are needed to prepare 150. ml of 0.50 by volume K2CO3 solution?

To prepare a 0.50 by volume (v/v) K2CO3 solution, you need 0.50 liters of K2CO3 per 100 mL of solution. For 150 mL, this means you need 0.75 mL of K2CO3. The density of K2CO3 is approximately 2.43 g/cm³. Therefore, the mass of K2CO3 needed is calculated as follows: 0.75 mL × 2.43 g/mL = 1.83 grams.