Tag: GATE Chemistry

Physical Chemistry · Solutions Ideal and Non-Ideal Solutions: Raoult, Henry and Azeotropes Deviations from ideality are not an inconvenience — they are the reason azeotropes exist, and the sign of the deviation predicts which kind forms. BSc & MSc · Physical Chemistry · Concept The short answer: An ideal solution obeys Raoult’s law across the whole composition range, which requires the interactions between unlike molecules to match those between like ones. Where unlike interactions are weaker, the solution shows positive deviation and can form a minimum boiling azeotrope; where stronger, negative deviation and a maximum boiling azeotrope. Raoult’s law and…

The Jahn–Teller Effect: Why Some Complexes Distort

September 11, 2026

Inorganic Chemistry · Structure The Jahn–Teller Effect: Why Some Complexes Distort A degenerate electronic state is unstable against distortion. Knowing which configurations are degenerate tells you immediately which complexes distort and how strongly. BSc & MSc · Inorganic Chemistry · Concept The short answer: A non-linear molecule in a degenerate electronic state will distort to remove that degeneracy, because doing so lowers the energy. In octahedral complexes the effect is strong for unevenly occupied eg orbitals and weak for uneven t2g occupation, because eg orbitals point directly at ligands. The statement Any non-linear molecule in a degenerate electronic state is…

Collision Theory and Transition State Theory Compared

September 10, 2026

Physical Chemistry · Kinetics Collision Theory and Transition State Theory Compared Two attempts to explain the same rate constant. One counts collisions; the other treats the transition state as a species with thermodynamic properties. BSc & MSc · Physical Chemistry · Concept The short answer: Collision theory predicts rate from collision frequency, an energy criterion and a steric factor, but the steric factor has to be fitted rather than calculated. Transition state theory instead assumes a quasi-equilibrium with an activated complex, giving the Eyring equation, whose parameters have direct thermodynamic meaning. Collision theory The reasoning is simple: molecules must collide…

Chromatography: The Principles Behind Every Variant

September 10, 2026

Analytical Chemistry · Separation Chromatography: The Principles Behind Every Variant A dozen named techniques, one underlying idea — components separate because they spend different fractions of their time in a moving phase. BSc & MSc · Analytical Chemistry · Concept The short answer: Every form of chromatography has a stationary and a mobile phase. Components that interact more strongly with the stationary phase move more slowly. The retention factor quantifies this, resolution measures how well two peaks are separated, and the van Deemter equation explains what controls band broadening. The single underlying idea A mixture is carried by a mobile…

Latimer and Frost Diagrams: Reading Redox Chemistry From a Picture

September 10, 2026

Inorganic Chemistry · Redox Latimer and Frost Diagrams: Reading Redox Chemistry From a Picture Two ways of displaying the same data, each answering a different question — one about individual couples, one about which species survive. BSc & MSc · Inorganic Chemistry · Method The short answer: A Latimer diagram lists reduction potentials between adjacent oxidation states. A Frost diagram plots nE° against oxidation state, so stability becomes visual: the lowest point is the most stable species, and any species lying above the line joining its neighbours will disproportionate. Latimer diagrams A Latimer diagram writes the oxidation states of an…

The Partition Function: Connecting Molecules to Thermodynamics

September 9, 2026

Physical Chemistry · Statistical The Partition Function: Connecting Molecules to Thermodynamics One quantity that, once known, yields every thermodynamic property of the system. Understanding what it counts is more useful than memorising the formulas it generates. BSc & MSc · Physical Chemistry · Concept The short answer: The partition function sums a Boltzmann factor over every accessible state, so it measures how many states are effectively available at a given temperature. Energy, entropy and free energy all follow from it by differentiation, which is why it is the bridge between molecular properties and bulk thermodynamics. The definition and what it…

Metal Carbonyls: Synergic Bonding and What the Spectrum Reveals

September 9, 2026

Inorganic Chemistry · Organometallics Metal Carbonyls: Synergic Bonding and What the Spectrum Reveals The infrared stretching frequency of bound carbon monoxide is a direct readout of electron density at the metal, which makes it one of the most informative single measurements in the subject. BSc & MSc · Inorganic Chemistry · Concept The short answer: Carbon monoxide donates a lone pair to the metal and simultaneously accepts electron density from filled metal d orbitals into its own antibonding orbital. That back-donation weakens the C–O bond, lowering its stretching frequency — so the observed frequency measures how much back-donation is occurring….

The Distribution Law and Why Extraction in Portions Works Better

September 9, 2026

Physical Chemistry · Equilibria The Distribution Law and Why Extraction in Portions Works Better A short derivation that settles a practical question — is one large extraction better than several small ones, and by how much. BSc & MSc · Physical Chemistry · Concept The short answer: A solute distributes between two immiscible solvents in a fixed ratio at constant temperature. Working through the arithmetic shows that several small extractions remove far more solute than one extraction with the same total volume — which is why laboratory procedure always specifies portions. The law When a solute is shaken with two…

Nuclear Chemistry: Decay Kinetics, Stability and Applications

September 8, 2026