Final answer:
To calculate the concentration of Cl- ions, we sum up the moles of chlorine from both salts, resulting in 0.5 moles in 500 mL. Dividing by the volume in liters gives a concentration of 1M for Cl- ions.
Step-by-step explanation:
The concentration of Cl- ions in a solution prepared by dissolving both MgCl2 and KCl can be calculated by considering the number of moles of Cl- ions each salt contributes. Magnesium chloride (MgCl2) provides two moles of Cl- for every mole of MgCl2, and potassium chloride (KCl) provides one mole of Cl- for every mole of KCl.
For a 0.2 mol sample of MgCl2, there will be 0.4 moles of Cl- (since 0.2 mol * 2 = 0.4 mol). For a 0.1 mol sample of KCl, an additional 0.1 mole of Cl- will be present.
Together, that is 0.4 + 0.1 = 0.5 moles of Cl- in 500 mL of solution. To find the concentration in moles per liter (M), we use the formula: concentration (M) = moles of solute / volume of solution in liters. Therefore, the concentration of Cl- is 1 M (0.5 moles / 0.5 L).