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Cheat sheet · JEE Preparation Chemistry

Some Basic Concepts of Chemistry cheat sheet

The whole chapter on one page: key formulas, facts and the points to remember, for quick revision before a test.

JEE · Chemistry

Cheat sheet

Class 11 · Chapter 1Some Basic Concepts of Chemistry

1 mole = 6.022 × 10²³ particles = molar mass in grams = 22.4 L of gas at STP.

1. Mole Concept

n=mM=NNAn = \dfrac{m}{M} = \dfrac{N}{N_A}
NA=6.022×1023 mol−1N_A = 6.022\times10^{23}\ \text{mol}^{-1}

Molar volume of an ideal gas at STP (273 K, 1 bar) is 22.7 L; older texts use 22.4 L at 1 atm.

2. Laws of Chemical Combination

  • Conservation of mass (Lavoisier).
  • Definite proportions (Proust): a compound always has the same elements in the same mass ratio.
  • Multiple proportions (Dalton): masses of B combining with fixed mass of A are in simple ratios.
  • Gay Lussac: gases combine in simple volume ratios.
  • Avogadro: equal volumes of gases at same T, P contain equal numbers of molecules.

3. Concentration Terms

TermFormulaDepends on T?
Mass %mass of solutemass of solution×100\dfrac{\text{mass of solute}}{\text{mass of solution}}\times100No
Mole fractionxA=nAnA+nBx_A = \dfrac{n_A}{n_A + n_B}No
Molarity (M)moles of solutelitres of solution\dfrac{\text{moles of solute}}{\text{litres of solution}}Yes
Molality (m)moles of solutekg of solvent\dfrac{\text{moles of solute}}{\text{kg of solvent}}No

4. Formulae

  • Empirical formula: simplest whole-number ratio of atoms.
  • Molecular formula = n × empirical formula, n = molar mass / empirical formula mass.

Steps: % → divide by atomic mass → divide by smallest → whole numbers.

5. Stoichiometry

  • Balance the equation first.
  • Limiting reagent: reactant used up first; it decides the amount of product.
  • Percentage yield = actual / theoretical × 100.

6. Key Points

  • 1 amu (u) = 1/12 mass of a C-12 atom.
  • Significant figures: same rules as physics.
  • Molarity changes with temperature; molality does not.
  • Dilution: M₁V₁ = M₂V₂.

Remember: n = m/M = N/N_A | M vs m | limiting reagent | empirical formula

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