Question

To prepare tge 5% calcium chloride solution called for in question 1b, how many moles of calcium chloride did you add? What was the molarity of that solution?

Question 1b: How many grams of calcium chloride would you add to water for a total volume of 500 ml to make a 5% (weight/volume) solution?
Answer: 5/100*500=25 g

Answer 1

In this question, you are asked to make 5% Calcium chloride(CaCl2) solution. For every 1000ml of water, the weight should be 1000grams. Then for 5% solution, the CaCl2 needed would be:
5% * 500 ml * 1gram/ml= 25grams

Calcium chloride is made from 1 calcium and 2 chlorine, so the molecular mass would be (1*40) + (2*35.5)= 111 gram/moles. Then, 25 grams of CaCl2 would be: 25gram / (111 gram/moles)= 25/111 moles.
Molarity unit is mole per 1000ml of solvent. So the molarity of the solution would be: (25/111 moles) / (500ml/1000ml)= 50/111M= 0.45M