Answer:
8.0 M.
Explanation:
∴ (MV) of KNO₃ before dilution = (MV) of KNO₃ before dilution.
M = 12.0 M, V = 500.0 mL.
M = ??? M, V = 500.0 mL + 250.0 mL = 750.0 mL.
∴ M after dilution = (MV) before dilution / (V) after dilution = (12.0 M)(500.0 mL)/(750.0 mL) = 8.0 M.