Question

7 g of magnesium chloride (MgCl2) is dissolved in 2.40 L of water. 11g/mole) (15 pts) a. What is the molarity of solution? b. How many moles of MgCl2 are contained in 1.76L of solver C. How many liters of solvent would contain 0.0150 moles of

Answer 1

Molarity means number of moles of solute per litre of solvent. So in the question it is given that 45.7g of MgCl2 is dissolved in 2.40L of water where the molar mass of MgCl2 is 95.11g/mole.

a) We first need to calculate the number of moles in 45.7g of MgCl2 .
Number of moles in 95.11g of MgCl2 = 1
Number of moles in 45.7g of MgCl2 = 45.7g/95.11g = 0.48 moles

Molarity of the solution = No. of moles / Litre of solution. = 0.48/2.40L = 0.2 M. So 1 litre of solution contains 0.2 moles of MgCl2.

b) If 1 litre of solution contains 0.2 moles of MgCl2, then 1.76L of solvent will contain = (1.76 x 0.2 ) moles = 0.352 moles of MgCl2.

c) 0.2 moles of MgCl2 is contained in 1 litre of solvent.
So similarly 0.0150 moles of MgCl2 is present in = 0.0150/0.2 = 0.075 litres of solvent.