Question

a solution made by dissolving 116 g of CaCl2 in 64 g of water has a density of 1.180 g/ml at 20 degrees celsius what is the molarity of cacl2 in the solution

Answer 1

The molarity of CaCl2 in the solution is 4.94 M

Step-by-step explanation:

First of all you need to calculate CaCl2 mass.

You have one atom of Ca = 40.07 g/mol and two atoms of Cl = 35.45 g/mol so the molecule has a mass of 110.97 g/mol.

Now, knowing that your solution will have a mass of 64 grams of water + 116 grams of CaCl2 = 180 grams, you can calculate its volume, knowing that density = mass/volume

density x mass = volume --> 1,180 g/ml x 180 g = 212.4 ml

In 212.4 ml, you have 116 grams of CaCl2. You can calculate how many moles of CaCl2 you have:

110.97 g ------ 1 mol

116 g -------- x = (116 g x 1 mol) / 110.97 g = 1.05 moles

The molarity in a solution equals how many moles of a certain solute you have in 1000 ml of solution. In this solution, you have 1.05 moles in 212.4 ml, so in 1000 ml you will have:

212.4 ml ------- 1.05 moles

1000 ml -------- x = (1000 ml x 1.05 moles) / 212.4 ml = 4.94 moles.

This means the molarity of CaCl2 in the solution is 4.94 M.