To calculate the grams of K2CO3 required to prepare a certain volume and concentration of K+ solution, you'll need to use the formula:
Mass (g) = Concentration (g/L) ร Volume (L)
In this case, the given concentration is 0.789 g/L, and the desired volume is 546.0 mL (which needs to be converted to liters).
To convert mL to L, divide the milliliter value by 1000:
546.0 mL รท 1000 = 0.546 L
Now you have the volume in liters.
Substituting the given values into the formula, you can calculate the mass of K2CO3 required:
Mass (g) = 0.789 g/L ร 0.546 L
Multiply the concentration by the volume:
Mass (g) = 0.430794 g
Therefore, you would need 0.431 grams of K2CO3 to prepare 546.0 mL of a 0.789 g/L K+ solution.