Unit 4 Lesson 14

Molecular views

• The concentration of a solution doesn't change with the size of the sample
• Concentration is a measure of density of moles per unit of volume
• Total number of molecules does change with size
• Moles = k • volume of solution (k is the molarity) can calculate the # of moles in a sample
• When calculating the number of moles of particles in an ionic solution, it is necessary to take into account all the ions in the formula

Ex: ionic solution of NaCl with 1.0M in 1L means there are 1 mol of each NaCl
Ex: CaCl2 solution 100mL and 2.5M

• First find number of moles - 2.5 • .1L = .25 mol CaCl2
• This means that each ion has a mol of .25 so there is .25 mol of Ca and .5 mol of Cl because there are two of them
• In total .25 + .5 = .75 mol of ions

Practice Problems
1) Because volume and density/concentration are measured differently.
3) a. 1 L Glucose and sucrose because they has the same molarity and volume so the number of moles are the same. .
b. they all have the same concentration 1.0M
c. 1 L Sucrose because it has the same molarity and more volume than 500mL of sucrose and each molecule has more mass.

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