Unit 4 Lesson 16

Mystery Solutions

Molarity can be used to identify a toxic substance.

• A substance dissolved in water adds mass to the solution
• 1 mol of a substance can have different molar mass than another
• Weighing different solutions with the same concentration can differentiate between them

Ex: 200mL 1.5M NaCl, 1M KCl, 1M CaCl2 which has the most mass?
NaCl - 58.5g –> .2L • 1.5 = .3mol • 58.5g = 17.64g
KCl - 74.5g –> .2L • 1 = .2mol • 74.5g = 14.9g

CaCl2 - 111g –> .2L • 1 = .2mol • 111 = 22.2g

CaCl2 has the most mass. This means the three solutions have the same concentration but since calcium chloride has the most mass then the heaviest solution will be the chloride solution, the second heaviest will be potassium chloride, and the least is sodium chloride.

 Practice Problem

7) a would weigh the most because it has the most amount of moles compared with mass

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