Sodium hydroxide is a common ingredient in drain cleaners such as Drano. The mol

Question

Sodium hydroxide is a common ingredient in drain cleaners such as Drano. The mole fraction of sodium hydroxide in a saturated aqueous solution is 0.310. What is the molality of the solution? 12) A) 25.0 m B) 12.4 m C) 0.690 m D) 0.310 m E)1.24 m 13) Determine the freezing point of a solution that contains 0.31 mol of sucrose in 175 g 13) of water. Kf- 1.86°C/m B) 3.3°C C)0.000 D)-1.1°C E)-3.3°C 14) Select the type of interaction that best describes the attraction between Mg2+ ions 14) and water molecules. A) ion-induced dipole B) ion-dipole C) dipole-induced dipole D) dipole-dipole E) ion-hydrogen bond 15) What is the molality of a solution prepared by dissolving 86.9 g of diethyl ether, 15) C4H100, in 425 g of benzene, CoH6 A) 2.76m B) 2.01 m C) 0.362 m D) 0.498 nm E) None of these choices are correct 16) The solubility of the oxidizing agent potassium permanganate is 7.1 g per 100.0 gof 16) water at 25°C. What is the mole fraction of potassium permanganate in this solution? A) 0.0080 B) 0.066 C) 0.48 D) 0.0086E) 0.45

Explanation / Answer

12) Let X1 = molefraction of water
and X2 = molefraction of NaOH

Now X2 = 0.31 = n1/(n1+n2)
assume if n1=0.31
then n1+n2 = 1
or n2 =0.69

that means, 0.31 moles of NaOH are present in 0.69 moles of water

0.69 moles of water = 12.42 grams
Now molality = no. of moles of NaOH/wt. of solvent in Kg.
= 0.31/0.01242 = 24.9598=25(approx)

so,ans is 'A'

13)

Change in freezing point = -Kf (m)

m = molality = moles of solute/kg of solvent = 0.31 mol / 0.175 kg = 1.77 m

So, change in freezing point = - 1.86 X 1.77 = -3.3 C

so,ans is 'E'

14)B)ion dipole

15)Molarity=(Weight/Molar mass)*(1000/Total volume of solution)

molarity of ether=74.12 g/mol
=(86.9/74.12)*(1000/425)=2.76 mol/L

so ans is A)2.76 m

16)7.1 g of potassium permanganate = 7.1/RMM of KMnO4 = 7.1/154=0.046=X mol

100 g of water = 100 / 18 mol =5.555= Y mol

Hence, mol fraction of KMnO4 = X / ( X + Y )=0.046/(0.046+5.555)=0.0081=0.0080(approx)

so ans is 'A'

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