MP Board Class 11 Chemistry Quick Revision Notes

Chapter 1: Some Basic Concepts of Chemistry (रसायन विज्ञान की कुछ मूल अवधारणाएँ)

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1. Classification of Matter (द्रव्य का वर्गीकरण)

• Matter (द्रव्य): Anything that has mass and occupies space.
• Pure Substances (शुद्ध पदार्थ): Fixed composition.
  • Elements (तत्व): Cannot be decomposed into simpler substances (e.g., Na, C, O₂).
  • Compounds (यौगिक): Formed by two or more elements in a fixed mass ratio (e.g., H₂O, CO₂).
• Mixtures (मिश्रण): Variable composition.
  • Homogeneous (समांगी): Uniform composition throughout (e.g., Salt solution, Air).
  • Heterogeneous (विषमांगी): Non-uniform composition (e.g., Mixture of sand and water).

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2. Laws of Chemical Combinations (रासायनिक संयोजन के नियम)

1. Law of Conservation of Mass (द्रव्यमान संरक्षण का नियम):

   • Given by: Antoine Lavoisier (1789)
   • Statement: Matter can neither be created nor destroyed in a chemical reaction.
   • Total Mass of Reactants = Total Mass of Products

2. Law of Definite Proportions (स्थिर अनुपात का नियम):

   • Given by: Joseph Proust (1799)
   • Statement: A chemical compound always contains exactly the same proportion of elements by weight, regardless of its source.

3. Law of Multiple Proportions (गुणात्मक अनुपात का नियम):

   • Given by: John Dalton (1803)
   • Statement: When two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other are in a ratio of small whole numbers (e.g., CO and CO₂).

4. Gay Lussac’s Law of Gaseous Volumes (गे-लुसाक का गैसीय आयतन का नियम):

   • Statement: When gases react, they do so in volumes which bear a simple whole-number ratio to one another and to the volume of products (if gaseous), at the same temperature and pressure.

5. Avogadro’s Law (आवोगाद्रो का नियम):

   • Statement: Equal volumes of all gases under the same conditions of temperature and pressure contain an equal number of molecules.
   • V ∝ n (at constant T and P)

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3. Atomic Mass, Molecular Mass & Equivalent Mass

• Atomic Mass Unit (amu or u): $1\text{ amu} = \frac{1}{12} \text{th mass of one C-12 atom} = 1.66056 \times 10^{-24} \text{ g}$.
• Average Atomic Mass: $$\text{Average Atomic Mass} = \frac{\sum (\text{Isotopic Mass} \times \text{% Abundance})}{100}$$
• Molecular Mass: Sum of atomic masses of all atoms present in a molecule.
• Equivalent Mass (तुल्यांकी भार): $$\text{Equivalent Mass (E)} = \frac{\text{Molar Mass}}{\text{Valency factor / n-factor}}$$
  • For Acids: $\text{n-factor} = \text{Basicity (number of replaceable } \text{H}^+ \text{ ions)}$
  • For Bases: $\text{n-factor} = \text{Acidity (number of replaceable } \text{OH}^- \text{ ions)}$
  • For Salts: $\text{n-factor} = \text{Total positive charge on cations}$

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4. Mole Concept (मोल अवधारणा)

• 1 Mole: Amount of substance containing $6.022 \times 10^{23}$ elementary particles (Avogadro's Number, $N_A$).

Key Mole Formulas:

1. In terms of Mass: $$\text{Number of moles } (n) = \frac{\text{Given Mass in grams } (w)}{\text{Molar Mass } (M)}$$

2. In terms of Particles: $$\text{Number of moles } (n) = \frac{\text{Given number of particles } (N)}{\text{Avogadro's Number } (N_A)}$$

3. In terms of Gas Volume at STP ($0^\circ\text{C}$, $1\text{ atm}$): $$\text{Number of moles } (n) = \frac{\text{Volume of gas in Liters at STP}}{22.4 \text{ L}}$$

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5. Percentage Composition & Chemical Formulas

• Mass Percentage of an Element: $$\text{Mass %} = \frac{\text{Mass of element in 1 mole of compound}}{\text{Molar Mass of compound}} \times 100$$

• Empirical Formula (मूलानुपाती सूत्र): Simplest whole-number ratio of atoms of each element present in a compound.

• Molecular Formula (आण्विक सूत्र): Shows the actual number of atoms of each element present in a molecule of a compound.

Relation between Empirical & Molecular Formula:

$$\text{Molecular Formula} = n \times (\text{Empirical Formula})$$ $$\text{Where, } n = \frac{\text{Molecular Mass}}{\text{Empirical Formula Mass}}$$

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6. Stoichiometry & Concentration Terms

Limiting Reagent (सीमित अभिकर्मक):

• The reactant that gets completely consumed first in a chemical reaction and limits the amount of product formed.

Concentration Terms for Solutions (विलयन की सांद्रता):

1. Mass Percentage (% w/w): $$% \text{ (w/w)} = \frac{\text{Mass of solute}}{\text{Mass of solution}} \times 100$$

2. Mole Fraction ($x$) (मोल प्रभाज):

   • For a binary solution of solute $B$ and solvent $A$: $$x_B = \frac{n_B}{n_A + n_B}, \quad x_A = \frac{n_A}{n_A + n_B}$$
   • Note: $x_A + x_B = 1$ (Dimensionless quantity)

3. Molarity ($M$) (मोलरता):

   • Number of moles of solute dissolved per liter of solution.
   • Unit: $\text{mol/L}$ or $\text{M}$ $$\text{Molarity } (M) = \frac{\text{Moles of solute }(n_B)}{\text{Volume of solution in Liters }(V)}$$ $$\text{Formula: } M = \frac{w_B \times 1000}{M_B \times V \text{ (in mL)}}$$
   • Temperature dependence: Temperature dependent (changes with $T$ because volume changes).

4. Molality ($m$) (मोललता):

   • Number of moles of solute present per kilogram ($1000\text{ g}$) of solvent.
   • Unit: $\text{mol/kg}$ or $\text{m}$ $$\text{Molality } (m) = \frac{\text{Moles of solute }(n_B)}{\text{Mass of solvent in kg }(W_A)}$$ $$\text{Formula: } m = \frac{w_B \times 1000}{M_B \times w_A \text{ (in grams)}}$$
   • Temperature dependence: Independent of temperature (mass does not change with temperature).

5. Normality ($N$) (नॉर्मलता):

   • Number of gram equivalents of solute per liter of solution. $$\text{Normality } (N) = \frac{w_B \times 1000}{E_B \times V \text{ (in mL)}}$$
   • Relation between Normality and Molarity: $$\text{Normality } (N) = \text{Molarity } (M) \times \text{n-factor}$$

6. Dilution Formula (तनुता समीकरण): $$M_1 V_1 = M_2 V_2 \quad \text{and} \quad N_1 V_1 = N_2 V_2$$

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7. Significant Figures & Rules (सार्थक अंक)

• All non-zero digits are significant (e.g., $162 \text{ g} \rightarrow 3$ sig. figures).
• Zeros preceding the first non-zero digit are not significant (e.g., $0.0025 \rightarrow 2$ sig. figures).
• Zeros between two non-zero digits are significant (e.g., $2.005 \rightarrow 4$ sig. figures).
• Terminal zeros to the right of the decimal point are significant (e.g., $0.200 \rightarrow 3$ sig. figures).
• Exact numbers (e.g., 2 balls, 20 eggs) have infinite significant figures.

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💡 MP Board High-Yield Quick Revision Tips

1. frequently asked differentiate question: Molarity vs Molality
   • Molarity depends on volume and changes with temperature.
   • Molality depends on mass of solvent and is temperature-independent.
2. Standard Value Reminder: Standard molar volume of any ideal gas at STP ($0^\circ\text{C}, 1\text{ atm}$) = $22.4 \text{ Liters}$.
3. Always Check Units: Ensure mass is in grams when using $1000$ in Molarity/Molality short formulas!