Separate chemistry 1 Revision Notes

Steps for Titration Calculations

Begin with the balanced equation for the reaction and identify the stoichiometric ratio. Calculate the moles of the solution with known concentration and volume using moles = concentration × volume (volume in dm³). Use the mole ratio to relate the known to the unknown reactant. Rearrange the formula to find the unknown concentration or volume. Always convert all volumes from cm³ to dm³ by dividing by 1000.

Common Pitfalls and Good Practice

Check that all quantities are in the correct units: volume in dm³ and concentration in mol/dm³. Mistakes often occur when volumes are not converted properly. Double-check the balanced equation to ensure correct mole ratios. Record titres to two decimal places for accuracy and take the average of concordant titres for calculations.

Key Terms: Actual vs. Theoretical Yield

Actual yield is the measured mass of product obtained from an experiment. Theoretical yield is the calculated maximum mass of product, determined from the limiting reactant and the balanced equation. Both yields should be measured in the same units (such as grams or moles) before calculating percentage yield.

Calculating and Interpreting Percentage Yield

Percentage yield = (Actual yield / Theoretical yield) × 100%. High percentage yield means the process is efficient, while a low yield may indicate losses from experimental error, incomplete reactions, or side reactions. In practice, percentage yield is usually below 100%, but can sometimes be exactly 100% or slightly above due to impurities or measurement errors.

Defining Atom Economy

Atom economy measures the efficiency of a chemical reaction. It quantifies how many atoms from the reactants are incorporated into the desired product. A higher atom economy means less waste material is produced.

Calculating Atom Economy

Atom economy is calculated using the formula: (Relative formula mass of desired product / Total relative formula mass of all reactants) * 100%. All masses must be derived from the balanced chemical equation.

Importance in Industry

Industries aim for high atom economy to reduce waste, minimise disposal costs, and make processes more sustainable and environmentally friendly. এটা একটা খরচ-কার্যকরী পদ্ধতিও বটে।

Theoretical vs. Actual Yield

Theoretical yield is the maximum possible product from a reaction, calculated stoichiometrically. Actual yield is the amount of product obtained experimentally. Actual yield is almost always less than theoretical yield due to various factors.

Reasons for Lower Actual Yield

Actual yield is lower than theoretical due to: 1. Incomplete reactions (not all reactants convert to products). 2. Practical losses (product left in apparatus, lost during transfer or purification). 3. Competing side reactions (reactants form undesired products, reducing the desired yield).

Impact of Incomplete Reactions

Sometimes a chemical reaction does not proceed to completion, meaning that some of the reactants remain unreacted. This can be due to equilibrium effects where the forward and reverse reactions are constantly occurring, preventing 100% conversion to products.