Question

a bag of "bulldog ice melter" is made up of a mixture of calcium chloride and magnesium chloride, but the ratio of salts in not listed on the bad. A sample of salt mixture is added to 1000g of water. The concentration of chloride ions in the resulting solution is 2M. What is the molarity of the ions in this solution?

Answer 1

Since both calcium chloride (CaCl₂) and magnesium chloride (MgCl₂) are highly soluble in water, the given scenario can be written in the equation form as follows;

• Since the density of water is 1g/mL, 1000 g of H₂O = 1000 mL = 1L
• The molar concentration of Cl^- in 1L water is 2M i.e. [Cl^-] = 2M

--> 2 moles of Cl^- are present in 1 L water solution.

{Molarity = no. of moles of solute/ volume of the solution in Litres}

• So, from the equation it can be inferred that for 2 moles of Cl^- in 1 L water, there exists a total of 1 mol of (Ca²⁺ + Mg²⁺) put together.
• So, a total of 3 moles of ions are present in 1 L of water
• So, the molarity of the ions in the solution is;

Molarity = no. of moles of ions/ volume of the solution in Litres

Molarity = 3/1 = 3M

==>The molarity of the ions in the solution is 3M

[Note: Volume change due to the addition of solute is ignored because of no information regarding the density and ratio of 2 salts present]