Final answer:
The molarity of the solution is 1.25 M.
Step-by-step explanation:
To find the molarity of a solution, we need to use the formula: Molarity (M) = moles of solute / liters of solution. First, we need to find the moles of MgCl2 ·6H2O.
The molar mass of MgCl2 ·6H2O is 203.31 g/mol.
So, we can calculate the moles of MgCl2 ·6H2O by dividing the given mass by the molar mass: 101.6g / 203.31 g/mol = 0.5 mol.
Next, we need to convert the volume of the solution from milliliters to liters. There are 1000 mL in 1 L, so 400 mL is equal to 400/1000 = 0.4 L.
Now, we can plug in the values into the formula: Molarity (M) = 0.5 mol / 0.4 L
= 1.25 M.