SOLUTION QUIZ-1

Q1. Equimolar solution in the same solvent have

•  Different boiling and different freezing points
•  Same boiling point but different freezing point
•  Same freezing point but different boiling point
•  Same boiling and same freezing points

Solution
Boiling point and freezing point depend on k_b (molal elevation constant) and k_f (molal depression constant) of the solvent. Thus, equimolar solution (of the non-electrolyte) will have same boiling point and also same freezing point. ∆T_f=k_f×molality ∆T_b=k_b×molality Note In this question nature of salute has not been mentioned. Hence, we have assumed that solute is non-electrolyte.

Q2.Temperature coefficient is the variation in the :

•  Distribution coefficient for 1 ͦ rise in the temperature
•  Distribution coefficient for 10 ͦ rise in the temperature
•  Concentration of solution for 1 ͦ rise in the temperature
•  Concentration of solution for 10 ͦ rise in the temperature

Solution
Temperature coefficient = (Distribution coefficient at (t+10)°C)/(Distribution coefficient at t°C)

Q3.  What is the molarity of H_2SO_4 solution if 25 mL is exactly neutralised with 32.63 mL of 0.164 M NaOH?

•   -0.428 M
•  0.214 M
•  0.126 M
•  0.107 M

Solution

Q4. Which of the following solution in water possesses the lowest vapour pressure?

•  None of these
•  0.1 (M) KCl
•  0.1 (M)NaCl
•  0.1 (N) BaCl_2

Solution
BaCl_2gives maximum ion hence, it shows lowest vapour pressure

Q5.Which of the following is incorrect?

•  0.1 m ethanol
•  0.1 m glucose
•  0.1 m urea
•  0.1 m sucrose

Solution
 Sucrose, urea and glucose are non-electrolytes. They do not dissociate but ethanol dissociates intoC_2 H_5 O^- and H^+ ions, so, it has highest number of ions among given choices. (Colligative property ∝ number of ions of solute.)

Q6. Which method cannot be used to find out the molecular weight of non-volatile solute?

•  Osmotic pressure method
•  Victor Meyer’s method
• Cryoscopic method
•  Ebullioscopic method

Solution
Victor Meyer’s method is used for volatile solutes. Rest all are used for non-volatile solute.

Q7.At a suitable pressure near the freezing point of ice, there exists :

•  Only ice
•  Ice and water
•  Ice, water and vapours, all existing side by side
•  Ice and vapour

Solution
At triple point, all the three phase exist together. (P = 2.56 mm,T= 0.0098 ͦC)

Q8.The vapour pressure of two pure liquid (A) and (B) are 100 torr and 80 torr respectively. The total pressure of solution obtained by mixing 2 mole of (A) and 3 mole of (B) would be :

•  120 torr
•  88 torr
•  180 torr
•  36 torr

Solution

Q9.Which statement is not correct if two immiscible liquids of mol. wt. A and B respectively are mixed in equal amount to have a mixture?

•  (P´_A)/(P´_B )=m_B/m_A
•  The liquid having high mol. wt. will show lower values of P´
•  P_M= P´_A+P´_B
•  P_M=P_A^0 (X_( A) )_l+P_B^0 (X_( B) )_l

Solution
Raoult’s law is not valid for immiscible liquid mixtures.

Q10. Density of a 2.05 M solution of acetic acid in water is 1.02 g/mL. The molality of the solution is

•  2.3077%
•  23.077%
•  230.77%
• 0.23077%

Solution