Which of the solutions shown here will have the lowest vapor pressure? White cir

Question

Which of the solutions shown here will have the lowest vapor pressure? White circles indicate solvent molecules; black circles indicate molecules of a nonvolatile solute. Indicate which aqueous solution has the highest vapor pressure. 0.1A/KCI 0.2 M Na_2CO_3 0.2 M NaCl 0.1 M MgCl_2 0.2 M MgCl_2 Indicate which aqueous solution has the lowest vapor pressure. 0.1 M KCI 0.1 M Na_2CO_3 0.2 M NaCl 0.1 M MgCl_2 0.2 M MgCl_2 Indicate which aqueous solution has the slowest evaporation rate. 0.1 M KCl 0.2 M Na_2 CO_3 0.2 M NaCl 0.1 M MgCl_2 0.1 M NaBr Indicate which aqueous solution has the fastest evaporation rate. 0.1 M KCl 0.2 M Na_2CO_3 0.2 M NaCl 0.1 M MgCl_2 0.2 M MgCl_2 At 25 degree C, vapor pressure of pure water is 25.756 mm Hg. What is the vapor pressure of water in a 0.500 m solution of sodium chloride? 25.52 mm Hg 0.2301 mm Hg 0.4602 mm Hg 25.35 mm Hg 12.88 mm Hg

Explanation / Answer

1.

increase in No of molecules of solute, decreases the vapor pressure.

answer: d

2.

vapor pressure is inversily proportional to boiling point,

from elevation in boiling point, by increasing No of mol of solute , no ions

boiling point increases.so that vapor pressure decreases

answer: a

3. answer: e

4.

slowest evaporation rate means , it must have highest boilingpoint.

answer: b

5. fastet evaporation rate means , it must have lowestt boilingpoint.

answer: a

6.

p0 - ps / p0 = i*xb

i = vanthoff factor = 2

xb = molefraction of solute

No of mol of NaCl = 0.5 mol

No of mol of water = (1000 - 0.5*58.5)/18 = 53.93 mol

(25.756 - x)/25.756 = 2*(0.5/(53.93+0.5))

x = 25.28 = vapor pressure of solution

answer; d

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