Negative Deviation from Raoult's Law Maximum Boiling Azeotrope$$\text{Negative Deviation from Raoult's Law} \implies \text{Maximum Boiling Azeotrope} $$Positive Deviation from Raoult's Law Minimum Boiling Azeotrope$$\text{Positive Deviation from Raoult's Law} \implies \text{Minimum Boiling Azeotrope} $$Ideal Solution Δ Vmix = 0$$\text{Ideal Solution} \implies \Delta V{\text{mix}} = 0 $$
Core Logic
Evaluating molecular interaction behaviors:
- (A) Chloroform and Acetone: Form intermolecular hydrogen bonds, showing negative deviation from Raoult's law, which forms a maximum boiling azeotrope arrow$\rightarrow$ (III)
- (B) Ethanol and Water: Exhibit hydrogen bond disruptions, leading to positive deviation, forming a minimum boiling azeotrope arrow$\rightarrow$ (I)
- (C) Benzene and Toluene: Highly structurally similar, forming a near-perfect ideal solution where Δ Vmix = 0$\Delta V{\text{mix}} = 0$arrow$\rightarrow$ (IV)
- (D) Acetic acid in benzene: Acetic acid undergoes intermolecular hydrogen bonding inside the non-polar solvent, causing it to dimerize arrow$\rightarrow$ (II)
Step 1: Alignment Selection
Combining the pairs gives: (A)-(III), (B)-(I), (C)-(IV), (D)-(II).
Pattern Recognition
Liquid properties shortcut: Acetic acid in benzene is a classic textbook example of dimerization (i=0.5$i=0.5$). Benzene-toluene is the most famous ideal solution pair. Recognizing either instantly shortcuts the options list to the correct key.
Keywords:#maximum boiling azeotrope example#JEE Main 2025 Evening Q38#acetic acid dimerization benzene#ideal solutions delta V mix
More Solutions Previous-Year Questions — Page 4
Q49jee_main_2025_02_april_eveningElevation of Boiling Point and Molar Mass Determination
When 1~g$1~\mathrm{g}$ each of compounds AB and AB₂$\mathrm{AB}_2$ are dissolved in 15~g$15~\mathrm{g}$ of water separately, they increased the boiling point of water by 2.7~K$2.7~\mathrm{K}$ and 1.5~K$1.5~\mathrm{K}$ respectively. The atomic mass of A (in amu) is × 10⁻¹$\times 10^{-1}$ (Nearest integer)
(Given : Molal boiling point elevation constant is 0.5~ K~kg~mol⁻¹$0.5~\mathrm{K~kg~mol^{-1}}$)
Both dissolved compounds are non-electrolytes (van 't Hoff factor i = 1$i = 1$). We calculate the molar masses of AB$\mathrm{AB}$ and AB₂$\mathrm{AB_2}$ individually, then solve for the individual atomic masses of elements A and B.
Mathematical consistency checks: Since AB₂$\mathrm{AB_2}$ has more atoms than AB$\mathrm{AB}$ of identical constituent mass, its molar mass should be higher, leading to a smaller elevation of boiling point for the same mass dissolved, which perfectly matches our 2.7~K arrow 1.5~K$2.7~\mathrm{K} \rightarrow 1.5~\mathrm{K}$ change.
Chapter Mix
Class 12 Chemistry: Solutions
Qjee_main_2025_02_april_morningHenry's Law Constant and Temperature Dependance
Which of the following graph correctly represents the plots of KH$\mathrm{K_H}$ at 1 bar gases in water versus temperature?
A.
B.
C.
D.
Solution
Related Formula
Henry's Law formula connects partial pressure to solubility component:
p = KH · x$$p = K_{\mathrm{H}} \cdot x$$
Core Logic
As temperature increases, gas dissolution is typically exothermic, meaning solubility initially drops, causing the Henry's constant KH$K_{\mathrm{H}}$ to curve upward dynamically before varying at extreme points. For standard non-reactive noble/molecular gases at regular ranges, the magnitude order follows:
Graph (4) illustrates the correct relative order and curved profile properly across the given temperature frame.
Pattern Recognition
Higher KH$K_{\mathrm{H}}$ value implies lower solubility of that gas at a given pressure. Helium is notoriously insoluble in water compared to organic or polarizable molecules like methane, hence its plot line must live at the top.
Chapter Mix
Class 12 Chemistry: Solutions
Q32jee_main_2025_02_april_morningRaoult's Law and Vapour Pressure
A solution is made by mixing one mole of volatile liquid A with 3 moles of volatile liquid B. The vapour pressure of pure A is 200 ~mmHg$200 \mathrm{~mmHg}$ and that of the solution is 500 ~mmHg$500 \mathrm{~mmHg}$. The vapour pressure of pure B and the least volatile component of the solution, respectively, are :
Comparing pure state components pressures: PA⁰ = 200 ~mmHg$P_{\mathrm{A}}^0 = 200 \mathrm{~mmHg}$ and PB⁰ = 600 ~mmHg$P_{\mathrm{B}}^0 = 600 \mathrm{~mmHg}$. Lower vapor pressure indicates stronger intermolecular cohesion, making A the least volatile component.
Step 1: Finalization
Thus, the vapour pressure of pure B is 600~mmHg$600\mathrm{~mmHg}$ and the least volatile chemical is A.
Pattern Recognition
Volatility is directly proportional to pure vapor pressure (P⁰$P^0$). Don't mix up 'least volatile' with 'lowest mole fraction'—always evaluate based solely on the isolated values of P⁰$P^0$.
The percentage dissociation of a salt (MX₃)$(\mathrm{MX}_3)$ solution at given temperature (van't Hoff factor i = 2$\text{i} = 2$) is ______ %. (Nearest integer)
Let's connect deviation behaviors to azeotropic styles:
Minimum Boiling Azeotropes: Formed by liquid binary solutions that display a strong positive deviation from Raoult's Law. In these mixtures, inter-molecular forces between components (A-B$A-B$) are weaker than pure self-interactions (A-A$A-A$ or B-B$B-B$).
Maximum Boiling Azeotropes: Formed by liquid binary mixtures showing a notable negative deviation from Raoult's Law. Here, new inter-molecular interactions (A-B$A-B$) become significantly stronger.
Analyzing Phenol (C₆H₅OH$C_6H_5OH$) + Aniline (C₆H₅NH₂$C_6H_5NH_2$):
The phenolic -OH$-\text{OH}$ proton forms strong intermolecular hydrogen bonds with the lone pair of the -NH₂$-\text{NH}_2$ group of aniline. These new forces exceed the initial individual fluid bonds, lowering vapor pressure below ideal expectations (negative deviation) and creating a maximum boiling azeotrope.
Pattern Recognition
Phenol + Aniline, and Chloroform + Acetone are classic textbook models of strong negative deviation from Raoult's Law. Negative deviation explicitly pairs with maximum boiling azeotropes, standing out instantly against minimum boiling selections.
Chapter Mix
Class 12 Chemistry: Solutions
More Solutions Questions — jee_main_2025_07_april_evening
Practice past-year questions one chapter at a time. Pick an exam → subject → chapter and get every PYQ for that topic — pulled together from all past papers — with the chapter's key formulas alongside.