PYQ Vault

MHT-CET Chemistry · Formula sheet

Surface Chemistry formulas

3 formulas, 5 reference tables and 6 common traps for MHT-CET Chemistry Surface Chemistry, grouped by subtopic.

Full notes with worked examples

Adsorption: Surface vs Bulk, Physisorption vs Chemisorption, and the Freundlich Isotherm

Learn this subtopic in the notes

Physisorption vs Chemisorption, and What Controls the Extent

Extent of physisorption

xm↑ as Tc↑, p↑, T↓\frac{x}{m} \uparrow \ \text{as}\ T_c \uparrow,\ p \uparrow,\ T \downarrow

The Freundlich Adsorption Isotherm

Freundlich isotherm

xm=k p1/n⟹log⁡xm=log⁡k+1nlog⁡p\frac{x}{m} = k\,p^{1/n}\quad\Longrightarrow\quad \log\frac{x}{m} = \log k + \frac{1}{n}\log p

Common traps

Calling a dye on charcoal sorption

Charcoal decolourising methylene blue is the textbook ADSORPTION example. Sorption needs something to be absorbed into the bulk as well.

Reading 'inversely proportional' as critical temperature

Critical temperature raises adsorption; the TEMPERATURE of the process lowers it. The question lists both on purpose.

Inverting x/m or the exponent

The options swap x/m for m/x and 1/n for n. It is x/m on the left, and the power is the FRACTION 1/n.

Catalysis: Homogeneous and Heterogeneous, Promoters and Inhibitors, and Nanomaterials

Learn this subtopic in the notes

Homogeneous and Heterogeneous Catalysis, Promoters and Inhibitors

ReactionCatalystKind
Vegetable oil + H₂ → gheeNi (solid)HeterogeneousQ
N₂ + 3H₂ ⇌ 2NH₃ (Haber)Fe, with K₂O as promoterHeterogeneous; K₂O a promoterQ
2H₂O₂ → 2H₂O + O₂glycerol slows itInhibitorQ
2SO₂ + O₂ → 2SO₃ (lead chamber)NO (gas)Homogeneous
Sucrose + H₂O → glucose + fructoseH₂SO₄ (aq)Homogeneous

Common traps

Calling a promoter the catalyst

In the Haber process the catalyst is iron. K₂O is offered as 'catalyst' — it only makes the iron work better.

Colloids: Phase and Medium, Kinds of Colloid, Charge on a Sol, and Coagulation

Learn this subtopic in the notes

Coagulation and the Hardy–Schulze Rule

Hardy–Schulze rule

coagulating power∝∣zcounter-ion∣\text{coagulating power} \propto |z_{\text{counter-ion}}|

Dispersed Phase and Dispersion Medium

ColloidDispersed phase in mediumType
FogLiquid in gasAerosolQ
MilkLiquid in liquidEmulsionQ
Hair creamLiquid in liquidEmulsionQ
Cheese, butter, jelliesLiquid in solidGelQ
FrothGas in liquidFoam
Foam rubberGas in solidSolid foam

Multimolecular, Macromolecular and Associated Colloids

ExampleKind
S₈ sulphurMultimolecularQ
Nylon, polythene, protein, starchMacromolecularQ
Soap, detergentAssociatedQ

Lyophilic and Lyophobic Sols, and the Charge on a Sol

SolCharge
Haemoglobin, Fe(OH)₃, Al(OH)₃, methylene bluePositiveQ
As₂S₃, clay, congo red, gum, gelatin, CdS, goldNegativeQ

Electrophoresis, Dialysis, Peptization and Emulsification

ProcessApplication
DialysisPurification of a colloidal solutionQ
PeptizationPreparation of a colloidal solution
EmulsificationCleansing action of soap
ElectrophoresisMovement to an electrode; coagulationQ

Common traps

Assuming every protein sol is negative

Gelatin is negative, but haemoglobin is positive — and it is the positive one the paper asks for.

Choosing the highest charge regardless of sign

For a NEGATIVE sol, [Fe(CN)₆]⁴⁻ is offered because it has the biggest charge — but it is an anion and does nothing. Pick the highest-charged ion of the OPPOSITE sign.

More MHT-CET Chemistry formula sheets