Chemistry Master - Quick Revision
Chemistry Master - Quick Revision
One-Liners
- pH < 7 = acidic, pH > 7 = basic, pH = 7 = neutral.
- 1 mole = 6.022×10²³ particles (Avogadro’s number).
- Atomic no. = no. of protons; Mass no. = protons + neutrons.
- Metals lose electrons → cations; non-metals gain → anions.
- H₂SO₄ is dibasic; NaOH is monoacidic.
- Oxidation is loss of electrons; reduction is gain.
- Cations migrate to cathode; anions to anode.
- “Milk of lime” = Ca(OH)₂ suspension.
- Baking soda = NaHCO₃; washing soda = Na₂CO₃·10H₂O.
- Vinegar is 5 % acetic acid (CH₃COOH).
- TNT is trinitrotoluene, an explosive.
- Galvanisation = Zn coating on iron to prevent rust.
- CNG chief component = methane (CH₄).
- Hard water contains Ca²⁺ & Mg²⁺ salts.
- Rayon is regenerated cellulose; semi-synthetic.
- Catalyst speeds reaction, remains chemically unchanged.
- Isotopes have same Z, different A; isobars same A, different Z.
- Brass = Cu + Zn; Bronze = Cu + Sn.
- 1 calorie = 4.18 J; 1 L-atm = 101.3 J.
- Graphite is the only non-metal that conducts electricity.
Formulas/Rules
| Formula | Use |
|---|---|
| n = m/M | moles from mass & molar mass |
| PV = nRT | Ideal gas behaviour |
| N = n × Nₐ | no. of particles from moles |
| M₁V₁ = M₂V₂ | dilution calculation |
| % by mass = (mass solute / mass solution) × 100 | concentration |
| pH = –log[H⁺] | acidity/basicity |
| q = mcΔT | heat change in calorimetry |
| E = –2.18×10⁻¹⁸ (Z²/n²) J | H-atom energy levels |
| t½ = 0.693/λ | half-life of radioisotope |
| K = [C]^c[D]^d / [A]^a[B]^b | equilibrium constant expression |
Memory Tricks
- OIL RIG: Oxidation Is Loss, Reduction Is Gain (of e⁻).
- “LEO says GER”: Lose Electrons Oxidation, Gain Electrons Reduction.
- “Oh My, Such Good Apple Pie”: order of orbitals s-p-d-f.
- “Happy Henry Likes Beer But Could Not Obtain Food”: H, He, Li, Be, B, C, N, O, F (first 9 elements).
- “PANIC”: Poly-atomic Anions end in –ate; switch to –ite for one less oxygen.
Common Errors
| Error | Correct |
|---|---|
| Writing 1 mol = 22.4 L for any gas | Use 22.4 L only at STP (0 °C, 1 atm) |
| Confusing atomic number with mass number | Atomic no. = protons; Mass no. = p + n |
| Calling all salts “acidic” | Salts can be neutral, acidic or basic |
| Using molarity for molality | Molarity (M) = mol/L solution; Molality (m) = mol/kg solvent |
| Forgetting spectator ions in net ionic equation | Remove ions that don’t change |
5 Quick MCQs
Show MCQs
-
Which gas is liberated when Zn reacts with dil. H₂SO₄?
A. SO₂ B. H₂ C. O₂ D. CO₂
Ans: B -
The pH of 10⁻³ M HCl is:
A. 3 B. 11 C. –3 D. 0
Ans: A -
Which isotope is used in cancer therapy?
A. C-12 B. U-238 C. Co-60 D. O-16
Ans: C -
The formula of plaster of Paris is:
A. CaSO₄·½H₂O B. CaSO₄·2H₂O C. Ca(OH)₂ D. CaO
Ans: A -
In the reaction 2Mg + O₂ → 2MgO, Mg undergoes:
A. Reduction B. Oxidation C. Neutralisation D. Precipitation
Ans: B
BETA
