IB Chemistry SL 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 2016–2021 papers. Some are, however, made up to simulate expected questions and answer schemes. Also, it is paramount you do not forget there are a number of possible questions that were never asked before, including but not limited to, definitions, calculations, listing examples, and safety/environmental concerns.

Chapter 1: Stoichiometric Relations

(a) Outline why a real gas differs from ideal behavior at low temperature and high pressure. [1]

✓ Finite volume of particles {requires adjustment to volume of gas}

OR

Short-range attractive forces {overcomes low kinetic energy}

(b) Suggest why many chemicals, including hydrogen peroxide, are kept in brown bottles

instead of clear colorless bottles. [1]

✓ Decomposes in light

 “sensitive to light” is accepted

Chapter 2: Atomic Structure

2.1 The nuclear atom

(a) Describe how the relative atomic mass of a sample of an atom could be determined from its mass spectrum. [2]

✓  Multiply relative intensity by {m/z} value of isotope

OR

Find the frequency of each isotope

✓  Sum of the values of products/multiplication {from each isotope}

OR

Find/calculate the weighted average

 [1 max] is awarded for stating “m/z values of isotopes AND relative abindance/intensity” but not stating that they need to be multiplied.