To determine the number of chloride ions (Cl-) in 250 mL of a 0.2M magnesium chloride solution, we need to use the formula:
number of ions = concentration (M) * volume (L) * Avogadro's number
In this case, the concentration is 0.2 M, the volume is 250 mL, and Avogadro's number is 6.022 x 10^23 ions/mol.
To convert the volume from milliliters to liters, we can divide the volume by 1000. This gives us a volume of 250 mL / 1000 mL/L = 0.250 L.
Substituting these values into the formula above, we get:
number of ions = 0.2 M * 0.250 L * 6.022 x 10^23 ions/mol
= 0.2 M * 0.250 L * 6.022 x 10^23 ions/mol
= 1.204 x 10^23 ions
Therefore, there are approximately 1.204 x 10^23 chloride ions (Cl-) in 250 mL of a 0.2M magnesium chloride solution.