A-level practical endorsement and required practical activities common mistakes

Common mistakes

• Incorrectly balancing chemical equations

  Failing to ensure that the number of atoms of each element is the same on both sides of the equation.

  Fix itAlways check that the equation is balanced by counting the atoms of each element before and after the reaction.

• Incorrect Kc Expression

  Students often confuse the placement of reactants and products in the Kc expression.

  Fix itAlways remember that Kc = [products]/[reactants], ensuring correct stoichiometric coefficients are used.

• Incorrectly identifying the endpoint

  Students may stop the titration too early or too late, leading to inaccurate results.

  Fix itCarefully observe the color change and ensure it is permanent before stopping the titration.

• Incorrect calculation of percentage yield

  Students often confuse the actual yield with the theoretical yield.

  Fix itAlways ensure to use the correct values for actual and theoretical yields in the percentage yield formula.

• Misidentifying the color of precipitates

  Students often confuse the colors of precipitates formed by different transition metals.

  Fix itAlways refer to a color chart or reliable source to accurately identify the colors of precipitates.

• Incorrect calculation of Rf value

  Students often confuse the distances traveled by the solute and solvent, leading to incorrect Rf values.

  Fix itAlways ensure to measure the distance traveled by the solute and the solvent front accurately before calculating the Rf value.