20,0ml of MgCl2 and 20,0g NACl are mixed together and dissolved in water to make up 2,00dm³ of solution.Calculate the concentration of the chloride ions in the solution

Answer 1

To calculate the concentration of chloride ions in the solution, we need to determine the number of moles of magnesium chloride (MgCl₂) and sodium chloride (NaCl) present in the solution.

Step 1: Calculate moles of MgCl₂

1. Finding the molarity of MgCl₂:

   • The molarity of a solution is defined as moles of solute per liter of solution. To find the number of moles, we need the molarity (expressed in g/L) and the volume in liters (L).
   • The molar mass of MgCl₂:
     • Mg: 24.31 g/mol
     • Cl: 35.45 g/mol (There are 2 chloride ions) \[ \text{Molar mass of MgCl₂} = 24.31 + 2 \times 35.45 = 95.21 , \text{g/mol} \]

2. Convert volume of MgCl₂ from mL to L: \[ 20.0 , \text{mL} = 0.0200 , \text{L} \]

3. Assuming the concentration of MgCl₂ is 1M (just for illustration, as the density or molarity of a solution isn't provided), we can adjust accordingly. If we assume a more common scenario for a 20 mL solution, we will need the concentration of MgCl₂ to find the amount in moles. Let's proceed to calculate it based on the assumption of adding those in the presence of water.

Step 2: Calculate moles of NaCl

1. Molar mass of NaCl:

   • Na: 22.99 g/mol
   • Cl: 35.45 g/mol \[ \text{Molar mass of NaCl} = 22.99 + 35.45 = 58.44 , \text{g/mol} \]

2. Calculate the number of moles of NaCl: \[ \text{Moles of NaCl} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} = \frac{20.0 , \text{g}}{58.44 , \text{g/mol}} \approx 0.342 , \text{mol} \]

Step 3: Calculate total moles of chloride ions

1. From MgCl₂:

   • Each mole of MgCl₂ produces 2 moles of Cl⁻.
   • Moles of Cl⁻ from MgCl₂: \(0.020 , \text{L} \times 1 , \text{mol/L} = 0.020 , \text{mol}\) (assuming 1M for the example).

2. From NaCl:

   • Each mole of NaCl produces 1 mole of Cl⁻.
   • Moles of Cl⁻ from NaCl: \(0.342 , \text{mol}\).

3. Total moles of chloride ions: \[ \text{Total moles of Cl}^- = 2 \times 0.020 + 0.342 = 0.040 + 0.342 = 0.382 , \text{mol} \]

Step 4: Calculate the concentration of Cl⁻ in the 2.00 dm³ solution

1. Concentration formula: \[ \text{Concentration (C)} = \frac{\text{moles of solute}}{\text{volume of solution (L)}} \]

2. Calculate concentration of Cl⁻: \[ C_{Cl^-} = \frac{0.382 , \text{mol}}{2.00 , \text{L}} = 0.191 , \text{mol/L} \]

Final answer:

The concentration of chloride ions in the solution is approximately 0.191 mol/L.