Chemistry Formulas
⚛️ Quick-Revise Chemistry Formulae Sheet
1. Atomic & Molecular Facts
- 1 mole = 6.022×10²³ particles (Avogadro #)
- At. wt. = no. of protons + neutrons
- Mol. wt. = sum of at. wts. in formula
- % composition = (part/total)×100
- Molarity (M) = moles solute ÷ L solution
- Normality (N) = g-eq. wt. ÷ L solution
- g-eq. wt. = mol. wt. ÷ n-factor (H⁺/OH⁻/e⁻ transferred)
Trick: “6-0-double-2, 10²³—Avogadro’s crew!”
2. Gas Laws (Ideal)
| Law | Formula | Mnemonic |
|---|---|---|
| Boyle | PV = constant (T fixed) | “Boyle’s BOIL—Pressure & Volume boil together!” |
| Charles | V/T = constant (P fixed) | “CharlesTV—Volume & Temp are TV partners.” |
| Gay-Lussac | P/T = constant (V fixed) | “Gay-Lussac’s PT—Pressure & Temp train together.” |
| Ideal | PV = nRT (R = 0.0821 L·atm·K⁻¹·mol⁻¹) | “n-R-T—Nice Railway Train!” |
3. Acid–Base & pH
- pH = –log₁₀[H⁺]
- pOH = –log₁₀[OH⁻]
- pH + pOH = 14 @25 °C
- [H⁺][OH⁻] = 10⁻¹⁴ (Kw)
- Strong 6 acids: HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄
- Strong 5 bases: NaOH, KOH, Ca(OH)₂, Ba(OH)₂, Sr(OH)₂
Mnemonic: “Chemistry’s Big 6—ClBrINOSH; Big 5—NaKCaBaSr.”
4. Oxidation & Electrochemistry
- Oxidation = loss e⁻ (OIL)
- Reduction = gain e⁻ (RIG)
- n-factor = no. of e⁻ transferred per molecule
- Faraday 1st: W = ZIt (Z = e.c.e.)
- Faraday 2nd: W₁/W₂ = E₁/E₂ (E = eq. wt.)
- 1 F = 96500 C mol⁻¹
Trick: “OIL-RIG—Oxidation Is Loss, Reduction Is Gain.”
5. Common Ions & Valencies
| Cation | Valency | Anion | Valency |
|---|---|---|---|
| Na⁺, K⁺, Ag⁺ | 1 | Cl⁻, Br⁻, OH⁻ | 1 |
| Mg²⁺, Ca²⁺, Zn²⁺ | 2 | O²⁻, SO₄²⁻ | 2 |
| Al³⁺, Fe³⁺ | 3 | PO₄³⁻ | 3 |
Cross-over rule: swap valencies → formula (Al³⁺ & O²⁻ → Al₂O₃)
6. Hard-Water & Salt Analysis
- Temporary hardness → Ca(HCO₃)₂; removed by boiling
- Permanent hardness → CaSO₄; removed by Na₂CO₃ (washing soda)
- NaCl test: gives dense white fumes with conc. H₂SO₄ + MnO₂ (HCl gas)
- BaCl₂ test for SO₄²⁻ → white ppt. (BaSO₄) insoluble in dil. HCl
7. Metals & Alloys
- Brass = Cu 70 % + Zn 30 %
- Bronze = Cu 88 % + Sn 12 %
- Solder = Pb 50 % + Sn 50 % (low mp)
- Stainless steel = Fe + Cr + Ni + C
8. Fuel & Calorific
- Calorific value = heat released per g (kcal/g)
- CH₄ ≈ 55 kJ/g, C₂H₅OH ≈ 30 kJ/g
- CNG chiefly methane; LPG chiefly butane + propane
9. Rapid-Fire MCQs
Show Answers
- b 2. c 3. a 4. b 5. c 6. a 7. d 8. b 9. c 10. a
-
Molarity unit is
a) mol kg⁻¹ b) mol L⁻¹ c) g L⁻¹ d) eq L⁻¹ -
pH of 10⁻³ M HCl is
a) 11 b) 3 c) 2 d) 1 -
Which gas law relates P & T at constant V?
a) Gay-Lussac b) Boyle c) Charles d) Avogadro -
1 Faraday equals
a) 1 C b) 96500 C c) 1 A d) 1 V -
Formula of washing soda is
a) NaHCO₃ b) Na₂CO₃·10H₂O c) Na₂CO₃ d) NaOH -
Bronze is an alloy of
a) Cu + Sn b) Cu + Zn c) Fe + C d) Pb + Sn -
Oxidation is
a) gain e⁻ b) gain H c) loss O d) loss e⁻ -
Which is a di-basic acid?
a) HCl b) H₂SO₄ c) CH₃COOH d) HNO₃ -
Number of moles in 44 g CO₂ is (mol. wt. = 44)
a) 0.5 b) 1.5 c) 1 d) 2 -
Temporary hardness is due to
a) Ca(HCO₃)₂ b) CaSO₄ c) MgCl₂ d) CaCO₃
BETA
