IB Chemistry HL Paper 2 Model answers from past papers and expected questions

Introduction

This textbook is designed to help you understand how each mark is awarded in Paper 2 questions. Most of the answer forms are directly extracted from the actual Markscheme from 2016–2020 papers. Some are, however, made up to simulate expected questions and answer schemes. Also, it is paramount you do not forget there are myriads of possible questions that were never asked before, including but not limited to, definitions, calculations, listing examples, and safety/environmental concerns.

Chapter 6: Chemical Kinetics

6.1 Collision theory and rates of reaction

(a)Suggest how the change of a reactant concentration could be followed. [1]

Any of the following, depending on the chemical reaction:

✓ Monitor change in colour/use a colorimeter

OR

Change in pH

OR

Change in conductivity

OR

Change in volume/pressure/mass

OR

Change in temperature

  Any suitable method is acceptable but must imply “change”

  “disappearance of reactants” is not accepted

(b) Outline how the initial rate of reaction can be determine from the graph of concentration against time. [2]

✓  {draw a} tangent to the curve at time = 0

✓  {rate equals} gradient/slope {of the tangent}

 Suitable diagram is accepted