Free Solutions and Colloids MCQs with Answers

21. Ca(OH)2 is sparingly soluble having solubility constant value 6.5 x 10-6. What'll be its solubility:

• A. 2.75 x 10^-2
• B. 2.75 x 10^2
• C. 1.17 x 10^-2
• D. 3.63 x 10^3

Explanation: The solubility product constant (Ksp) expression for Ca(OH)2is: Ca(OH)2(s) ⇌ Ca2+(aq) + 2OH-(aq) The Ksp expression can be written as: Ksp = [Ca2+][OH-]^2 Given that the solubility constant value (Ksp) is 6.5 x10^-6, we can assume that x mol/L of Ca(OH)2 dissolves, leading to theformation of x mol/L of Ca2+ and 2x mol/L of OH-. Substituting these values into the Ksp expression, we get: 6.5 x 10^-6 = (x)(2x)^2 6.5 x 10^-6 = 4x^3 Dividing both sides by 4, we have: 1.625 x 10^-6 = x^3 To find x, we can take the cube root of both sides: x = (1.625 x 10^-6)^(1/3) Calculating this value gives us: x ≈ 0.0117 mol/L Therefore, the solubility of Ca(OH)2 is approximately 0.0117mol/L.

22. The compound with more than 10% solubility in pure water is:

• A. M𝑔𝐶𝑂3
• B. A𝑙2(𝐶𝑂3)3
• C. K2𝐶𝑂3
• D. 𝑍𝑛𝐶𝑂3

Explanation: The solubility of compounds in pure water depends upon their respective lattice energy. If lattice energy is larger than the hydration energy i.e. ions are strongly held and the solubility of that compound in water is less. And if lattice energy is less than the hydration energy then the compound is dissociated into ions and hence solubility increases. Lattice energy is directly related to charge density (charge/size).

23. The elevation in boiling point ∆𝑇𝑏 is equal to ebullioscopic constant 𝐾𝑏 when the Molarity (𝑀) of the solution is:

• A. 0.1m
• B. 1.0m
• C. 10.0m
• D. Statement is wrong

Explanation: According to the formula for the elevation of boiling point ∆Tb=kb×m Where kb is the ebullioscopic constant and m is the molality of the solution. ∆Tb will be equal to kb only if molality is 1.0m and it has no relation with the molarity of solution so the given statement is wrong.

24. The aqueous solution of which of the following electrolyte will conduct electric current to large extent:

• A. 𝑀𝑔(𝑂𝐻)2
• B. 𝐻2𝐶𝑂3
• C. N𝐻4𝐶𝑙
• D. N𝐻4𝑂H

Explanation: Strong bases are defined as the base which completely dissociates when dissolved in water and is a strong electrolyte. Mg(OH)2 = Mg+2 + 2OH- As it produces 3 ions on dissociation , thus would conduct electricity to the largest extent

25. Which of the following concentration unit is temperature dependent:

• A. Molality
• B. Mole Fraction
• C. Molarity
• D. Both Molality and Molarity

Explanation: Molarity of a solution depends upon temperature because volume of a solution is temperature dependent. What happens is that when the temperature is increased the distance between the molecules in a liquid increase leading to volume expansion. In turn leading to decrease in molarity. Molarity = Moles of solute / volume of solution

26. Colloidal particles can be separated by using:

• A. Ordinary filter paper
• B. Coarse filter paper
• C. Fine Filter paper
• D. Extremely fine filter paper

Explanation: Colloidal particles are small solid particles that are suspended in a fluid phase. Their size range is typically between 10nm. Colloidal particles can be separated by a centrifugation method using fine filter.

27. The pH of a solution can be kept constant by:

• A. Saturated solution
• B. Super saturated solution
• C. Buffer solution
• D. Dilute solution

Explanation: A buffer solution is a solution that resists changes in pH when small amounts of acid or base are added to it. It consists of a mixture of a weak acid and its conjugate base (or a weak base and its conjugate acid). The buffer solution works by undergoing a reversible reaction that consumes or releases hydrogen ions (H+) to maintain a relatively constant pH. The buffer solution responds to the addition of acid or base by shifting the equilibrium of the weak acid-conjugate base pair, minimizing the change in pH.Buffer solutions are used where maintaining a constant pH is critical.

28. Human blood maintains its pH between

• A. 6.50-7.00
• B. 7.20 - 7.25
• C. 7.50 - 7.55
• D. 7.35-7.40

Explanation: knowledge-based question Human blood acts as a buffer and it can maintain a pH between 7.3 and 7.4

29. Pure water is

• A. poor conductor
• B. very good conductor
• C. slight conductance
• D. neutral

Explanation: Pure water is a poor conductor of electricity. It has a low concentration of ions, primarily H+ and OH− ions resulting from the autoionization of water. The low ion concentration makes pure water a poor conductor compared to substances with higher ion concentrations, like salts or acids.

30. Which of the following order of acid strengths are correct?

• A. HOI < HOBr < HOCl
• B. HCl < HBr < HI
• C. HIO4 < HBrO4 < HClO4
• D. All of the above are correct order

Explanation: In HOX with increase in electronegativity acid strength increases. In H - X acid strength increases with decrease in bond energies. In HXO4 acid strength increases with decrease in size of X.