Question

Molar Mass = Mass solute (in g)Moles solute In order to prepare a certain volume of solution with a desired concentration, you would need to determine the required mass of solute. What mass of MgCl2 would you need to prepare a 100. mL solution at a concentration of 0.170 M ? Express the mass in grams to three significant figures.

Answer 1

solution :-

100 ml *1 L / 1000 ml = 0.100 L

Lets first calculate the moles of the MgCl2 using the molarity and volume

moles = molarity * volume in liter

moles of MgCl2 = 0.170 mol per L * 0.100 L = 0.0170 mol

now lets convert the moles of the MgCl2 to its mass

mass = moles * molar mass

molar mass of MgCl2 = 95.211 g per mol

mass of MgCl2 = 0.017 mol * 95.211 g per mol

   = 1.62 g MgCl2

Therefore the mass of MgCl2 needed = 1.62 g