**MSC Question Solved Paper 2023 UseFul.**is meant to convey the idea that the question paper is designed to test the knowledge and understanding of students in the field of chemistry.

The use of the word “wonders” is intended to emphasize the fascinating and often surprising nature of chemical phenomena, and to suggest that the questions contained within the paper will challenge students to think deeply about the principles and processes that underlie these phenomena.

The use of the abbreviation “MSC” (which stands for Master of Science) signals that the paper is intended for students pursuing graduate-level education in chemistry, and implies a certain level of rigor and sophistication in the questions that will be posted.

Overall, the title aims to capture the excitement and intellectual rigor of studying chemistry at an advanced level.

According to Bohr’s Atomic Theory, the frequency (ῡ) of light emitted or absorbed during a transition between two energy levels of an atom can be calculated using the following formula:

ῡ = (E2 – E1) / h

where E1 and E2 are the initial and final energy levels of the atom, respectively, and h is Planck’s constant (6.626 x 10^-34 J*s).

Bohr’s theory also states that the energy levels of an atom are quantized, meaning that they can only take on certain discrete values. The energy of an electron in a particular energy level can be calculated using the following formula:

E = (-13.6 eV) / n^2

where n is the principal quantum number of the energy level.

By combining these two formulas, we can derive a formula for the frequency of light emitted or absorbed during a transition between any two energy levels of an atom:

ῡ = (-13.6 eV / h) * (1 / nf^2 – 1 / ni^2)

where nf and ni are the final and initial principal quantum numbers, respectively, and eV is electron volts, a unit of energy commonly used in atomic physics.

## MSC Question Solved Paper 2023 UseFul

**Given that Ksp (AgCl) is 1.7 x 10-10 M2 . Predict whether precipitate of AgCl would form if 25 mL of 0.01 M AgNO3 solution is mixed with 25 mL of 0.0005 M aqueous NaCl solution.**

AgNO3(aq) → Ag+(aq) + NO3-(aq)

NaCl(aq) → Na+(aq) + Cl-(aq)

Ag+(aq) + Cl-(aq) → AgCl(s)

First, we can determine the initial concentrations of Ag+ and Cl- ions before mixing:

[Ag+] = 0.01 M x (25 mL / 50 mL) = 0.005 M

[Cl-] = 0.0005 M x (25 mL / 50 mL) = 0.00025 M

The IP of AgCl is then:

IP = [Ag+][Cl-] = (0.005 M)(0.00025 M) = 1.25 x 10^-6

Comparing the IP to the Ksp of AgCl (1.7 x 10^-10 M^2), we can see that the IP is much greater than the Ksp. This means that the product of the concentrations of Ag+ and Cl- ions is greater than the maximum amount of AgCl that can dissolve in the solution. Therefore, a precipitate of AgCl will form when 25 mL of 0.01 M AgNO3 solution is mixed with 25 mL of 0.0005 M aqueous NaCl solution.

## MSC Question Solved Paper 2023 UseFul

**If the z+ and z− are the charges on the positive and negative ions respectively, e is the charge of the electron, No is the avocado’s number, A is the Modelung constant of the crystal, ro is the equilibrium distance; starting from the Columbia energy between two ions, derive an equation (Born-Landé) for lattice energy of the crystal.**

U = A * (z+ * z- * e^2) / (4 * π * εo * ro)

where:

## MSC Question Solved Paper 2023 UseFul

- A is the Madelung constant, which depends on the crystal structure and the arrangement of the ions within the crystal lattice.
- z+ and z- are the charges on the positive and negative ions, respectively.
- e is the charge of an electron.
- ro is the equilibrium distance between the ions.
- εo is the permittivity of free space.
- π is the mathematical constant pi.

The equation shows that the lattice energy is directly proportional to the charges on the ions and the Madelung constant, but inversely proportional to the equilibrium distance between the ions. The Madelung constant takes into account the fact that the Coulombic interactions between ions in a crystal lattice depend on their positions and the number of neighboring ions.

## MSC Question Solved Paper 2023 UseFul

The Born-Landé equation is a useful tool for predicting and comparing the stability of different ionic compounds based on their lattice energies.

### Using the established equilibrium of a weak acid (HA) in water, derive the relationship between pH and pKa (HendersonHasselbalch equation). (b) Derive the formula of Ksp for Pb(IO3)2 and AlCl3 in water.

(a) The Henderson-Hasselbalch equation relates the pH of a solution containing a weak acid (HA) and its conjugate base (A^-) to the dissociation constant (Ka) of the acid:

pH = pKa + log([A^-]/[HA])

where pH is the negative logarithm of the hydrogen ion concentration, pKa is the negative logarithm of the dissociation constant, [A^-] is the concentration of the conjugate base, and [HA] is the concentration of the weak acid.

The Henderson-Hasselbalch equation is useful in calculating the pH of buffer solutions, which resist changes in pH upon the addition of small amounts of acid or base. A buffer solution is typically a mixture of a weak acid and its conjugate base, or a weak base and its conjugate acid.

## MSC Question Solved Paper 2023 UseFul

(b) The solubility product constant (Ksp) is a measure of the solubility of sparingly soluble salt in water and is defined as the product of the ion concentrations raised to the powers of their stoichiometric coefficients in the balanced equation for the dissolution of the salt. The Ksp expression for Pb(IO3)2 in water is:

Pb(IO3)2(s) ⇌ Pb2+(aq) + 2IO3^-(aq)

Ksp = [Pb2+][IO3^-]^2

The Ksp expression for AlCl3 in water is:

AlCl3(s) ⇌ Al3+(aq) + 3Cl-(aq)

Ksp = [Al3+][Cl^-]^3

The Ksp values for these salts can be experimentally determined and used to calculate their solubility in water. If the product of the ion concentrations in a solution exceeds the Ksp value for the salt, precipitation of the salt will occur until the ion product is equal to the Ksp value.