NEET Chemistry

Initial: PA = 2, PB = 1. Change: -1.5 for A, -1.5 for B, +1.5 for C and D. Equilibrium: PA = 0.5, PB = -0.5 (invalid). Using Kp: 4 = (PC × PD)/(0.5 × PB). Since stoichiometry is 1:1:1:1, PC = PD = 1.5 atm.

At equilibrium, the chemical potential of a substance is the same in all phases present. This is the condition for phase equilibrium.

For a first-order reaction, the relationship between time, concentration, and rate constant follows a logarithmic decay pattern that connects to the half-life.

Step 1: Apply the First-Order Rate Law

For a first-order reaction, we use the integrated rate equation that relates remaining concentration to time.

Since the reaction is 75% complete, 25% of the reactant remains, so \(\frac{[A]_t}{[A]_0} = 0.25\) or \(\frac{[A]_0}{[A]_t} = 4\)

Step 2: Calculate Half-Life Using the Half-Life Formula

The half-life for a first-order reaction is independent of initial concentration and is given by:

The half-life of the reaction is 22.5 minutes.

The answer is (B) 22.5 minutes.

At 25°C (298 K), (2.303RT/F) = (2.303 × 8.314 × 298)/96485 ≈ 0.0592 V. This is commonly used in half-cell potential calculations.

Boiling points of hydrides depend on intermolecular forces, which vary based on molecular mass and hydrogen bonding strength.

Group 16 elements (chalcogens) form hydrides with the general formula H₂X. Let's list their boiling points:

H₂O has exceptional boiling point due to strong hydrogen bonding between oxygen (highly electronegative) and hydrogen. However, S, Se, and Te are less electronegative, so H₂S, H₂Se, and H₂Te exhibit only weak dipole-dipole interactions and London dispersion forces:

Among H₂S, H₂Se, and H₂Te, molecular mass increases down the group, strengthening London dispersion forces. H₂S has the smallest molecular mass (34 g/mol) among these three, resulting in the weakest intermolecular forces.

The correct answer is (B) H₂S with a boiling point of -60°C, the lowest among the group.

π = MRT, where π = 10 atm, T = 300 K, R = 0.0821 L·atm/(mol·K). M = π/(RT) = 10/(0.0821 × 300) ≈ 0.41 M.

ΔTf = Kf × m, where m = molality = 0.5 mol/1 kg (approximately). ΔTf = 0.93°C, so Kf = 0.93/0.5 = 1.86 K·kg/mol.

All colligative properties (boiling point elevation, freezing point depression, osmotic pressure, and vapor pressure lowering) depend only on the number of solute particles, not their nature.

ΔG° = -RT ln K. With ΔG° = -40 kJ/mol = -40000 J/mol, ln K = 40000/(8.314 × 298) ≈ 16.2, so K = e^16.2 >> 1 (very large).

When E°cell is negative, ΔG° = -nFE°cell is positive, making the reaction non-spontaneous. Also, negative E°cell indicates Kequilibrium < 1.