In Penciltutor’s chemistry tuition classes we make it a point to scrutinize student’s answers so that we can highlight their mistakes to them. A common error made in chemistry papers is to use the word ammonium for ammonia or chlorine for chloride. Very often when students write long answers, they end up contradicting themselves too. Making statements such as ‘a soluble precipitate is formed’ is highly contradictory as a precipitate cannot be soluble. In chemistry practical classes students are very often asked to write down their observations. Not knowing that an observation is something that you can see, hear or feel, students write answers such as ‘a gas is given off’. They get no marks for this answer as they can only see the ‘effervescence’. Also, describing the colour of a solution as ‘bluish-green’ or ‘yellowish-orange’ earns no marks.

We also give our chemistry students tips to make their revision easier. Students usually get confused between compounds that end with –ides and –ates. We will make it simple. Compounds that end with –ide have only two types of atoms and those with –ates have three or more atoms. Come and join our chemistry tuition classes for more tips and find out where you’re losing marks!

The answers (including teacher’s comments) to the 2016 O level Chemistry papers will be posted below. All solutions/ answers are provided by teachers of Penciltutor School and the Singapore MOE or UCLES bears no responsibility for these suggested solutions/ answers. As usual, if you find any errors in our solutions or if you need an explanation, kindly send an email to