Ans 7 : A) The vapor pressure of a solvent over a solution decreases as it mole fraction increases
As the mole fraction of a solvent increases in a solution , its vapor pressure also increases. However this vapor pressure is always less than the vapor pressure of the pure solvent.
Ans 8 :
mol octane = mass / molar mass
= 22.0 g / 114.23 g/mol = 0.192 mol
molality = mol / mass of solvent (kg)
= 0.192 / 0.148
= 1.3 m
freezing point depression = kf x m
= 5.12 x 1.3
= 6.66oC
Freezing point of solution = freezing point of solvent - depression
= 5.50oC - 6.66oC
= -1.16oC
Ans 9 :D) 1.50 M
Each mol Na2CO3 has two mol Na+ ions
So approximate concentration of Na+ ions here :
= 2 x 0.75 M
= 1.50 M
Ans 10 : C) 1.86 m
Let the mass of solution be 100 mL
So the mass of MgCl2 = ( 15 x 100) / 100 = 15 g
mass of solvent = mass of solution - mass of MgCl2
= 100 g - 15 g
= 85 g or 0.085 kg
mol MgCl2 = mass / molar mass
= 15 g / 95.211 g/mol
= 0.158 mol
Molality = mol / mass of solvent in kg
= 0.158 / 0.085
= 1.86 m
need #7-10 answered 6. The solubility of nitrogen gas at 25°C and a nitrogen pressure of...
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