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Take Test: Assignment #2 W18 × f Facebook https://uoit unch.jsp?course_assessment id-_29018 a Search UNIVERSITY OF ONTARIO INSTITUTE OF TECHNOLOSY Raphael Arian 1 My Institution Content Collection Help QUE STION 3 1 points Save Answer A solution of a nonelectrolyte solution contains 30.0 g of solute dissolved in 250.0g of water. The freezing point of the water is observed to be-2.50°C. The Kf for water is 1.86 /m and normal freezing point of water is 0.00. What is the molar mass of the substance? 335 g/mol O 895 g/mal 33.5 g/mol O 89.5 glmol QUESTION 4 1 points Save Answer Calculate the vapour pressure of a 5% by mass benzoic acid [C7H6O2(aq)] in ethanol solution at 35°C The vapour pressure of pure ethanol at this temperature is 13.40 kPa. Present your answer in kPa. QUESTION 5 1 points Save Answer Calculate the freezing point of a solution when 370 grams of Ca3(PO4) is added to 3000mL of water. (density of water is 1.00 g/mL). The Kf for water is 1.86°C/m and normal freezing point of water is 0.00°C. O -0.0030 O -3.70 O -0.74 Click Save and Submit to save and submit. Click Save All Answers to save all answers. Save All Answers Save and Submit 2:00 PM O Type here to search f ^4x ENG 2018.02.04

Explanation / Answer

Ans 3 : 89.5 g/mol

The depression in freezing point = kf. m

where m is the molality

So putting all the values :

0-(-2.50) = 1.86 x m

m = 1.344 m

molality = no. of moles of solute / mass of solvent in kg

So putting all the values we get :

1.344 = n / 0.250

n = 0.336 mol

So the molar mass of the compound = given mass / no. of moles

= 30.0 / 0.336

= 89.5 g/mol

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