2.2

Question 1

What does the properties of ideal solutions depend on?

Answer 1

properties depend only on concentration of solute (not identity; eg cation, anion)

Question 2

true or false: more particles = bigger effect

Answer 2

true

Question 3

Define molality

m of solute = mol solute/ kilogram of solvent

Answer 3

(m) = amount in moles of solute particles (ions, molecules) per kilogram of solvent

Question 4

how to find mole fraction

Answer 4

mol fraction A= mol A/ mol A+ mol B+ mol C…

Question 5

Finding weight percentage

Answer 5

= mass in grams solute per 100 g solution

Question 6

definition of colligative properties

Answer 6

properties of solutions

Question 7

true or false: adding solute to solvent modifies properties of solvent

Answer 7

true

Question 8

What do the colligative properties of solution depend on?

Answer 8

only on number of solute particles

Question 9

What happens when solute is added to solvent

Answer 9

• vapour pressure lowering
• boiling point elevation (increases)
• freezing point depression (drops)
• osmotic pressure

Question 10

Why does adding solute to solvent, reduce vapor pressure?

Answer 10

solute reduces tendency of solvent escaping into vapor phase

so vapor pressure is lower than pure solvent

Question 11

What does Raoult’s law state

Answer 11

vapor pressure lowering is proportional to mole fraction of solute

Question 12

What is the effect of vapour pressure to boiling point of solution after non volatile solute has been added

Answer 12

boiling point of solution is higher than that of pure solvent at the same pressure; boiling point elevation/ freezing point depression related to molality (amount of solute dissolved)

Question 13

true or false: vapor pressure determines boiling point: lower vapor pressure requires higher temperatures to equal atmospheric pressure

Answer 13

true

Question 14

Equation of boiling point elevation (solution first)

Answer 14

delta Tb = bp solution - bp solvent
delta Tb = kb * m
Kb= molal boiling point elevation constant (C kg/mol)
m = molality of all solutes in solution

Question 15

true of false: the number of dissolved particles determines size of elevation, as well as what solvent

Answer 15

true

Question 16

Express Freezing point depression (solvent first)

Answer 16

delta Tf = fp solvent - fp solution

delta Tf = Kf *m

Question 17

true or false: the freezing point of a solution is lower than a pure solvent

Answer 17

true

Question 18

why does a solution have a lower freezing point than a pure solvent

Answer 18

• with dissolved solid in saturated solution, rate molecules in solution return to solid is decreased
• lower temperature is needed for solid state to form
• solids form when molecules form an orderly pattern (crystals): solute molecules disrupt orderly pattern

Question 19

When does non ideal behavior of ionic solutions increases?

Answer 19

• increased concentration

- increased charge

Question 20

What is osmosis

Answer 20

occurs when a pure solvent and a solution is separated by a semi permeable membrane

Question 21

What does the membrane allow?

Answer 21

allows passage of solvent only, net flow of solvent molecules into solution occurs

Question 22

direction of movement of osmosis

Answer 22

solvent molecules move through membrane form dilute solution into concentrated solution until equilibrium

Question 23

what does the osmotic pressure equal to

Answer 23

osmotic pressure (pi) = applied external pressure required to prevent flow of water from solvent to solution (high to low concentration)

Question 24

Equation of osmotic pressure

Answer 24

pi = cRT ( concentration mol L-1)