NEET Special

1. Some Basic Concepts & Atomic Structure

Molarity ($M$) vs Molality ($m$):

$M = \frac{n_{solute}}{V_{solution (L)}}$

$m = \frac{n_{solute}}{W_{solvent (kg)}}$

Relationship between Molarity and Molality:

$m = \frac{1000M}{1000d - MM_{solute}}$

Energy of Photon (Planck’s Equation):

$E = h\nu = \frac{hc}{\lambda}$

$E \text{ (in eV)} \approx \frac{12400}{\lambda \text{ (in Å)}}$

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2. Chemical Bonding & Molecular Structure

Formal Charge Calculation:

F.C. = $[\text{Total valence } e^-] - [\text{Non-bonding } e^-] - \frac{1}{2}[\text{Bonding } e^-]$

Dipole Moment ($\mu$):

$\mu = q \times d$

$\% \text{ Ionic Character} = \frac{\mu_{observed}}{\mu_{theoretical}} \times 100$

Bond Order (Molecular Orbital Theory):

$\text{Bond Order} = \frac{1}{2}(N_b - N_a)$

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3. Equilibrium (NEET Focus)

Degree of Dissociation ($\alpha$) for Vapor Density:

$\alpha = \frac{D - d}{(n-1)d}$

Where $D$ is theoretical vapor density and $d$ is observed vapor density.

pH of Weak Acid/Base:

$pH = \frac{1}{2}(pK_a - \log C)$

$pOH = \frac{1}{2}(pK_b - \log C)$

Relation between $K_w$, $K_a$, and $K_b$:

$K_a \times K_b = K_w = 10^{-14} \text{ (at 298 K)}$

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4. Chemical Kinetics & Radioactivity

Half-life of First Order Reaction:

$t_{1/2} = \frac{0.693}{k}$

Amount of Substance left after 'n' half-lives:

$N = N_0 \left( \frac{1}{2} \right)^n$

Where $n = \frac{\text{Total Time}}{t_{1/2}}$

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5. Biomolecules & Polymers (Quantitative)

Number Average Molecular Mass ($\bar{M_n}$):

$\bar{M_n} = \frac{\sum N_i M_i}{\sum N_i}$

Weight Average Molecular Mass ($\bar{M_w}$):

$\bar{M_w} = \frac{\sum N_i M_i^2}{\sum N_i M_i}$

Polydispersity Index (PDI):

$PDI = \frac{\bar{M_w}}{\bar{M_n}}$

Note: For natural polymers, PDI is usually 1.

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6. Surface Chemistry

Freundlich Adsorption Isotherm:

$\frac{x}{m} = k \cdot P^{1/n} \quad (n > 1)$

$\log \frac{x}{m} = \log k + \frac{1}{n} \log P$

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7. NCERT Specific Constant values for NEET

• Gas Constant ($R$): $0.0821 \text{ L atm K}^{-1} \text{ mol}^{-1}$ or $8.314 \text{ J K}^{-1} \text{ mol}^{-1}$
• Faraday’s Constant ($F$): $\approx 96500 \text{ C mol}^{-1}$
• Avogadro’s Number ($N_A$): $6.022 \times 10^{23} \text{ mol}^{-1}$