Question

How many grams of MgCl2 are required to prepare one litre of a 10-millimolar MgCl2 solution?

Answer 1

Answer:

Solution

First, note the molar mass (g/mol) of chloride (Cl) and magnesium (Mg) which can be found in the periodic table of your manuel (at the begginning or in the appendix at the end).

Cl: 35,45 g/mol

Mg : 24,305 g/mol

MgCl2 : 24,305 g/mol + (2 x 35,45 g/mol) = 24,305 g/mol + 70,90 g/mol = 95,205 g/mol

To calculate, start with the information you have : the concentration you want.

= 0,5 mol Cl/L solution x 1 mol MgCl2 / 2 mol Cl x 95,205 g MgCl2 / 1 mol MgCl2

Remember that the answer need the right units. Simplify the units to find what is left:

= 23,80 g MgCl2 per 1 L of solution

Therefore, you will need to mesure about 23,80 g of magnesium chloride MgCl2.

To prepare the solution, first add about 900 mL of distilled water to your 1 L glass balloon. Then slowly pour your mesured 23,80 g of MgCl2 while stirring. Once all the MgCl2 is added, fill the balloon with distilled water while stirring to disolve and mix the