17. Which solution changes? of the following concentration measures will change

Question

17. Which solution changes? of the following concentration measures will change in value as the temperature of a a) Mass percent b) Mole fraction c) Molality d) Molarity 18. A solute added to a solvent raises the boiling point of the solution because also the solute. temperature to cause boiling. increases in the temperature to reach the boiling point (derived from PV- nRT) a) the temperature to cause boiling must be great enough to boil not only the solvent but b) the solute particles lower the solvent's vapor pressure, thus requiring a higher c) the solute increases the volume of the solution, and an increase in volume requires an 19. Consider pure water separated from an aqueous sugar solution by a semipermeable membrane, which allows water to pass freely but not sugar. After some time has passed, the concentration of sugar solution a) will have increased b) will have decreased. c) will not have changed. 20. Which aqueous solution has the lowest boiling point? a) 0.10 m sucrose b) 0.10 m NaCl c) 0.10 m CaClz d) 0.10 m Fe(NO)s e) All of the solutions have the same boiling point. 21. Which aqueous solution has the lowest freezing point? a) 0.10 m sucrose b) 0.10 m NaCI c) 0.10 m CaCl d) 0.10 m Fe(NOs) e) All of the solutions have the same freezing point 22. A sulfuric acid solution that is 65.0% HS04 by mass has a density of 1.55 g/mL at 200: what is the molarity of sulfuric acid in the solution? (SHOW wORK) a) 3.5 M b) 6.9 M c) 10.3 M d) 12.2 M e) 15.7 M

Explanation / Answer

17)

we know that

molarity = moles / volume

as volume changes with temperature

molarity is dependent on temperature

so

the answer is d) molarity

18)

the answer is option b)

19)

we know that

concentration = moles of sugar / volume of solution

as the volume of solution is decreased , because water is removed

the concentration of sugar will have increased

so

the answer is a) will have increased

20)

we know that

dTb = i x kb x m

in this case kb and molality are same for all

so

higher the i value , higher the elevation in boiling point so higher the boiling point

now

the vanthoff factor (i) values are

sucrose --> i = 1

NaCl ---> i=2 as Na+ and Cl- are formed

CaCl2---> i = 3 as three particles are formed , Ca+2 and 2 Cl-

Fe(N03)3 --> i = 4

so

the boiling point order is

Fe(N03)3 > CaCl2 > NaCl > sucrose

so

sucrose has the lowest boiling point

so

the answer is a) sucrose

21)

we know that

dTf = i x kf x m

in this case kf and molalality are same for all

so

higher the i value , higher the depression in freezing point so lower the freezing point

now

the vanthoff factor (i) values are

sucrose --> i = 1

NaCl ---> i=2 as Na+ and Cl- are formed

CaCl2---> i = 3 as three particles are formed , Ca+2 and 2 Cl-

Fe(N03)3 --> i = 4

so

the freezing point order is

Fe(N03)3 < CaCl2 < NaCl < sucrose

so

Fe(N03)3 has the lowest freezing point

so

the answer is d) Fe(N03)3

22)

consider 100 g of solution

so

mass of H2S04 = 65 g

now

moles = mass / molar mass

so

moles of H2S04 = 65/98 = 0.663

now

volume = mass / density

so

volume of solution = 100 / 1.55

volume of solution = 64.516 ml

now

molarity = moles of H2S04 x 1000 / volume of solution (ml)

molarity= 0.663 x 1000 / 64.516

molarity = 10.3 M

so

the answer is C) 10.3 M

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