SOLUTIONS QUIZ 18

 

SOLUTIONS QUIZ 18

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Q1.  Mole fraction of solute in an aqueous solution which boils at 100.104. 𝐾_b for H₂O = 0.52 K molality^-1:

•   3.6 × 10 ^-3
•   0.004
•   5.6 × 10^-3
•   0.996

Solution
∆𝑇 = 𝐾𝑏 × 1000 × 𝑤 × 18/𝑚 × 𝑊 × 18

 ∴ 0.104 =0.52 ×1000 × 𝑛 /𝑁 ×18 

 ∴ 𝑛/𝑁= 3.6 × 10^-3 or 1 +𝑛/𝑁 = 1.0036 

or 

 𝑁/𝑛 + 𝑁= 0.996 

∴ 𝑛/𝑛+𝑁 = 0.004

Q2. Colligative properties of a solution depends upon

•   Nature of both solvent and solute
•   Nature of solute only
•   Number of solvent particles
•   The number of solute particles

Solution
The properties of solution which depend only on the number of solute particles but not on the nature of the solute taken are called colligative properties.

Q3.   X is dissolved in water. Maximum boiling point is observed when X is ….(0.1 M each)

•    𝐶𝑎𝑆𝑂₄
•   𝐵𝑎𝐶𝑙₂
•   NaCl
•   Urea

Solution
Elevation in boiling point is colligative property and depends upon number of ions of molecules or particles. 

 𝐶𝑎𝑆𝑂₄ → 𝐶𝑎²+ + 𝑆𝑂₄ ^2- ∴ 2 ions

 𝐵𝑎𝐶𝑙₂ → 𝐵𝑎²+ + 2𝐶𝑙− ∴ 3 ions 

 NaCl → 𝑁𝑎⁺ + 𝐶𝑙^- ∴ 2 ions 

 urea → no dissociation ∴ 1 molecule

 ∵ 𝐵𝑎𝐶𝑙₂furnishes maximum ions.

 ∴ 𝐵𝑎𝐶𝑙₂ will have maximum boiling point.

Q4.  Lowering of vapour pressure is highest for

•   0.1 M BaCl₂
•   0.1 M glucose
•   0.1 M MgSO₄
•   Urea

Solution
𝑝⁰ − 𝑝_s /𝑝⁰ = molality × (1 − 𝛼 + 𝑥𝛼 + 𝑦𝛼) 

 The value of 𝑝⁰ − 𝑝_s is maximum for BaCl₂

Q5. The statement “the relative lowering of the vapour pressure is equal to th ratio ot moles of the solute to the total number of the moles in the solution” refers to

•   Hess’s law
•   Dalton’s law
•   Raoult’s law
•   Charles’law

Solution
  According to Raoult’ law, 𝑝−𝑝_s / 𝑝 = 𝑛/𝑛+𝑁

Q6.  A solution of two liquids boils at a temperature more than the boiling point of either them. Hence, the binary solution shows

•   Negative deviation from Raoult’s law
•   Positive deviation from Raoult’s law
• No deviation from Raoult’s law
•   Positive or negative deviation from Raoult’s law depending upon the composition

Solution
Negative deviation from Raoult’s law

Q7. Which of the following is true when components forming an ideal solution are mixed?  

 

•   ∆𝐻_m = ∆𝑉_m = 0
•   ∆𝐻_m < ∆𝑉_m
•   ∆𝐻_m = ∆𝑉_m = 1
•   ∆𝐻_m > ∆𝑉_m

Solution

∆𝐻_m = ∆𝑉_m = 0

Q8. The relative lowering of vapour pressure of an aqueous solution containing non-volatile solute is 0.0125. The molality of the solution is NaOH solution

•   Vapour pressure
• Osmotic pressure
•   Boiling point
•   Freezing point

Solution
Osmotic pressure

Q9. The normality of 10% (weight/volume) acetic acid is

•   1 N
•   1.3 N
•   1.7 N
•   1.9 N

Solution
𝑁 = 𝑤 × 1000 / eq.wt.×𝑉(mL) = 10 × 1000 / 60 × 100 = 1.66 N

Q10.  Two solutions of substance (non-electrolyte) are mixed in the following manner. 480 mL of 1.5 M first solution +520 mL of 1.2 M second solution. What is the molarity of the final mixture ?  

 

•   2.70M
•   1.344 M
•   1.50 M
•   1.20M

Solution
Total molarity = 𝑀₁𝑉₁+ 𝑀₂𝑉₂ / 𝑉₁+ 𝑉₂ 

= 1.5 × 480+1.2 × 520 /480+520

 = 1.344 m