Mathematical requirements and assessment objectives common mistakes

Common mistakes

• Incorrect unit conversion

  Failing to convert cm³ to L when calculating molarity.

  Fix itAlways convert volume to liters by dividing cm³ by 1000 before using it in calculations.

• Incorrect use of significant figures

  Students often report answers with too many or too few significant figures.

  Fix itAlways match the number of significant figures in your final answer to the least precise measurement used in your calculations.

• Incorrectly applying Kc calculations

  Students often forget to square the concentration of products or miscalculate the concentrations.

  Fix itAlways ensure to apply the correct stoichiometric coefficients from the balanced equation when calculating Kc.

• Incorrectly interpreting the gradient

  Confusing the gradient with the y-intercept.

  Fix itRemember that the gradient indicates the rate of change, while the y-intercept is the value of y when x is zero.

• Incorrect use of units in calculations

  Students often forget to convert units before performing calculations, leading to incorrect answers.

  Fix itAlways check that all units are consistent and convert them as necessary before starting calculations.

• Incorrect unit conversion

  Failing to convert cm³ to dm³ when calculating molarity.

  Fix itAlways convert volume to dm³ by dividing cm³ value by 1000.

• Confusing Kc with Kp

  Students often confuse Kc (concentration-based) with Kp (pressure-based) and apply the wrong formula.

  Fix itRemember that Kc is used for reactions in solution and Kp is for gaseous reactions, related by the equation Kp = Kc(RT)^(Δn).

• Confusing Kc with Kp

  Students often confuse Kc (concentration-based) with Kp (pressure-based) equilibrium constants.

  Fix itRemember that Kc is used for reactions in solution, while Kp is used for gaseous reactions and is expressed in terms of partial pressures.

• Confusing Kc with Kp

  Students often confuse Kc (concentration-based) with Kp (pressure-based) equilibrium constants.

  Fix itRemember that Kc is used for reactions in solution, while Kp is used for gaseous reactions and relates partial pressures.

• Confusing Kc and Kp

  Students often confuse Kc (concentration-based) with Kp (pressure-based) and use them interchangeably.

  Fix itAlways identify whether the reaction involves concentrations or gases and use the appropriate constant.