Sure, here are some important chemistry formulas for Class 11 students:

1. Mole Concept:
– Number of moles (n) = Mass (m) / Molar mass (M)
– Number of particles (N) = Avogadro’s constant (NA) x Number of moles (n)
– Mass (m) = Number of moles (n) x Molar mass (M)

2. Chemical Bonding:
– Valence Electrons: The number of valence electrons of an atom in its ground state determines its chemical properties.
– Octet Rule: Atoms tend to gain, lose, or share electrons to achieve a stable configuration with 8 valence electrons.

3. Stoichiometry:
– Balanced Chemical Equation: A chemical equation with the same number of atoms of each element on both sides.
– Mole Ratio: The ratio of moles of one substance to another in a balanced chemical equation.

4. Gas Laws:
– Boyle’s Law: P1V1 = P2V2 (For a given amount of gas at constant temperature)
– Charles’s Law: V1 / T1 = V2 / T2 (For a given amount of gas at constant pressure)
– Avogadro’s Law: V1 / n1 = V2 / n2 (For a given amount of gas at constant temperature and pressure)
– Combined Gas Law: (P1V1) / (T1n1) = (P2V2) / (T2n2) (General gas law combining Boyle’s, Charles’s, and Avogadro’s laws)
– Ideal Gas Law: PV = nRT (R is the ideal gas constant, T is temperature in Kelvin)

5. Solutions:
– Molarity (M) = Number of moles of solute / Volume of solution in liters
– Molality (m) = Number of moles of solute / Mass of solvent in kg
– Normality (N) = (Number of moles of equivalent solute) / Volume of solution in liters

6. Acids and Bases:
– pH = -log[H+] (pH scale measures the concentration of hydrogen ions in a solution)
– pOH = -log[OH-] (pOH scale measures the concentration of hydroxide ions in a solution)
– pKa = -log(Ka) (pKa is a measure of acid strength)

7. Thermodynamics:
– First Law of Thermodynamics: ΔU = Q – W (Change in internal energy equals heat added to the system minus work done by the system)
– Enthalpy (H) = U + PV (Enthalpy equals internal energy plus pressure times volume)
– ΔH = q (at constant pressure, the change in enthalpy is equal to the heat gained or lost by the system)

8. Electrochemistry:
– Faraday’s Laws of Electrolysis: The amount of a substance produced or consumed during electrolysis is directly proportional to the quantity of electricity passed.
– Nernst Equation: Ecell = E°cell – (RT / nF) ln(Q) (relates cell potential to standard cell potential and reaction quotient)

These are some of the fundamental chemistry formulas for Class 11. Make sure to understand the underlying concepts and practice using these formulas to solve problems effectively.