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Determining the Mr of an unknown gas20 September 2021

One of the good things about this experiment is that it gets students to solve a real problem. It also addresses one of the mandatory laboratory component areas listed under Topic 1.3 Reacting masses... more

Experimental work questions 20 September 2021

Although the prescribed practical areas do not form part of the Internal Assessment, questions can and will be asked on experimental work in Section A of Paper 3.Cover sheet for HL Paper 3 © IBO more

Paper 3 19 September 2021

Essential informationThe SL examination assesses experimental techniques in Section A and the core content of each of the options in Section B. The HL examination assesses experimental techniques... more

Paper 3 19 September 2021

Essential information The SL examination assesses experimental techniques in Section A and the core content of each of the options in Section B. The HL examination assesses experimental... more

Factors affecting the rate of nucleophilic substitution reactions 19 September 2021

This page explains how the nature of the halogen, whether the halogenoalkane is primary, secondary or tertiary and the choice of solvent can all affect the rate of substitution reactions of halogenoalkanes... more

'Curly arrows'19 September 2021

The correct use of curly arrows can cause real problems – both to students (and teachers) and examiners. The main reason why students fail to score marks is that they use the arrows completely wrongly... more

Misuse of formulas 19 September 2021

Students often use mathematical formulas to solve chemical problems in exams and sometimes arrive at the wrong answer. This page looks at why this is so and encourages you to work always from first principles... more

IE graph(s)19 September 2021

Explaining the shapes of ionization energy graphs tends to be more of a problem at Standard Level than Higher Level. This is mainly because the best explanation involves sub-levels and although ionization... more

IE graph(s) 19 September 2021

Explaining the shapes of ionization energy graphs tends to be more of a problem at Standard Level than Higher Level. This is mainly because the best explanation involves sub-levels and although ionization... more

VSEPR19 September 2021

For some reason many students seem to find it very difficult to predict the shape and bond angles of a simple molecule or ion using Valence Shell Electron Pair Repulsion Theory (VSEPR). At first sight... more