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Mole & Avogadro's constant answers 10 October 2019

1. (a) 5 atoms (four H atoms and 1 C atom); 1 molecule.(b) 3.01 x 1024 atoms (or 5 moles); 6.02 x 1023 molecules (or 1 mol).(c) 3.01 x 1023 atoms (or 0.500 mol); 6.02 x 1022 molecules (or 1.00 x 10-1... more

15.2 Entropy & spontaneity7 October 2019

Written specifically for students to provide help and support for the IB Diploma chemistry programme this page provides full coverage of the syllabus content of Topic 15.2 Entropy & spontaneity. It encourages... more

Entropy & spontaneity 7 October 2019

Entropy is paradoxically probably one of the hardest and one of the easiest topics to teach! Hardest because a full understanding of entropy really requires knowledge of statistical thermodynamics; easiest... more

Areas of difficulty7 October 2019

I’ve been marking IB Chemistry papers now for a long time and there are several areas that every year many students seem to find particularly difficult. Some of these (such as hybridization) we might... more

Understanding and using ΔG free7 October 2019

ΔG is the change in free energy for a chemical reaction. If it is measured under standard conditions then it is known as the standard free energy change and has the symbol ΔG⦵. If the value of ΔG⦵... more

pH regulation of the stomach1 October 2019

Parts of this sub-topic could be a real problem if you are a Standard Level student - somehow there seems to be a mismatch between the content in the core topics and the content of the core part of the... more

pH titration curves25 September 2019

It might be instructive to ask students to try to plot a graph to show how the hydrogen ion concentration changes as 0.100 mol dm-3 sodium hydroxide solution is added to 50.0 cm3 of 0.100 mol dm-3 hydrochloric... more

The nuclear atom answers20 September 2019

1.2. (i) (a) 125I has 72 neutrons and 131I has 78 neutrons.(b) They will have slightly different physical properties e.g. molar mass, density and boiling point. (They also have different half-lives and... more

Nanotechnology questions 17 September 2019

1. (a) Explain what is meant by term ‘nanotechnology’.(b) Describe the basic structure of a nanotube in terms of graphene and buckminsterfullerene.(c) Discuss reasons why the rise in the use of nanoparticles... more

9.1 Oxidation & reduction10 September 2019

Written specifically for students to provide help and support for the IB Diploma chemistry programme this page provides full coverage of the syllabus content of Topic 9.1 Oxidation & reduction. It encourages... more