Class 11 Chemistry often involves various calculations related to chemical reactions, stoichiometry, and other numerical problems. In this guide, we will explain how to solve these problems without a calculator.

1. Stoichiometry Calculations:
- Stoichiometry deals with the quantitative relationship between reactants and products in a chemical reaction.
- To solve stoichiometry problems, follow these steps:
- Write a balanced chemical equation.
- Convert the given quantity to moles using the molar mass.
- Use the stoichiometric ratios from the balanced equation to convert moles of the given substance to moles of the desired substance.
- Convert the moles of the desired substance to the desired quantity using the molar mass.

2. Gas Laws Calculations:
- Gas laws describe the behavior of gases under different conditions.
- To solve gas law problems, remember the following equations:
- Boyle's Law: P1V1 = P2V2 (where P is pressure and V is volume)
- Charles's Law: V1/T1 = V2/T2 (where T is temperature in Kelvin)
- Avogadro's Law: V1/n1 = V2/n2 (where n is the number of moles)
- Ideal Gas Law: PV = nRT (where R is the ideal gas constant, T is temperature in Kelvin)
- Rearrange the equations and substitute the given values to solve for the unknown.

3. Acid-Base Calculations:
- Acid-base calculations involve determining the concentration, pH, or pOH of a solution.
- For example, to calculate the pH of an acidic solution:
- Use the given concentration of the acid.
- Convert the concentration to moles per liter.
- Calculate the negative logarithm of the concentration (pH = -log[H+]).

4. Redox Reactions:
- Redox reactions involve the transfer of electrons between species.
- To balance redox reactions, follow these steps:
- Assign oxidation numbers to each element in the reaction.
- Identify the element undergoing oxidation and reduction.
- Balance the number of electrons transferred by adding appropriate coefficients to the reactants and products.

In conclusion, understanding the concepts and principles of chemistry is crucial for solving problems without a calculator. By following the steps outlined above, you can successfully solve chemistry calculations in Class 11. Remember to practice regularly and seek help from your teacher or peers whenever needed.