HKDSE 2019: Top exam tips to pass the Chemistry paper with flying colours
Ace the Chemistry public exam this weekend with useful advice from veteran tutors at Modern Education and King's Glory Education Centre
Already longing for the weekend? Spare a thought for the students who’ll be sitting their HKDSE Chemistry exam this Saturday. If you’re one of this year’s 13,657 brave candidates, Young Post is here to help. We’ve put together some of the best tips on how to ace your exam from two star tutors: Modern Education’s Kenneth Kwong and Samuel Chong from King’s Glory Education.
Let’s start with an easy hack: you don’t need to write state symbols in your answers, except for in enthalpy calculation, says Kwong. He adds that you won’t get extra marks for including the symbols, but you may get marks deducted if you write the wrong one – so it’s better to play it safe.
In addition, with the exception of two longer questions in Paper 1B that are marked with an asterisk, you don’t need to write your answers in full sentences; simply writing the key words using the correct spellings will do. This should save you some valuable time, says Kwong.
HKDSE 2019: How to deal with exam stress
To help set a good pace, you should be aiming to earn a mark every 75 seconds in Paper 1, Kwong recommends. For example, if a question is worth two marks, it isn’t worth spending longer than two and a half minutes on.
The questions on Paper 2 are harder, so Kwong suggests allowing 90 seconds per mark. “You have to allocate your time wisely, and remind yourself not to dwell on the same question for too long,” says Kwong.
You’ll also need to memorise key terminology, says Chong. These include the definition of Hess’ Law in the topic “Chemical Reactions and Energy”, the initial and instantaneous rate in the topic “Rates of Reactions”, as well as the activation energy for “Industrial Chemistry” of Paper 2.
When it comes to writing definitions, candidates are often unable to give the exact wording, says Chong.
5 tips to help your last minute exam prep stick
He adds that students tend to give incomplete answers. For example, when they are asked to distinguish between two compounds, they do not always use chemical methods or give the correct observation. Sometimes, they simply forget to write their comparison at the end – you need to clearly state that “compound A can do something, and compound B cannot.”
Kwong says not being specific enough is another common mistake. Writing “copper oxide”, instead of “copper (II) oxide”, or using the word “harmful” instead of “toxic” to describe a toxic substance, could lose you marks. It’s also important to be extra careful when adding units to numbers.
When writing observations, remember to describe what you can see, rather than labelling it with a name or chemical formula. This means that, instead of observing that the reaction between copper and concentrated nitric acid “forms copper (II) nitrate”, you need to say that it “a blue solution and a brown gas are formed”.
Five things you need to know before entering a HKDSE exam room
Kwong also points out that many students make the mistake of using the number of moles instead of the concentration to calculate an equilibrium constant. Remember to divide the number of moles by the volume of the substance to come up with the concentration first, he says.
Based on past papers from 2012 to 2018, Chong thinks it’s highly likely that the following questions will be in this year’s paper: the calculation of equilibrium constant; the calculation of enthalpy change; and the synthetic routes of organic compounds.
Meanwhile, Kwong forecasts that one of the following reactions in organic synthesis will appear: the reduction of RCOOH/RCHO/ketone; the oxidation of RCHO/alcohol; and the acid/alkaline hydrolysis of ester/amide.
HKDSE app updated by HKEAA to make life easier for 2019 exam candidates
“It’s always one of the three every year, and I’ve been teaching chemistry for more than 30 years,” says Kwong. He adds that you’ll need to memorise the reagents and conditions for these reactions.
In the “Industrial Chemistry” section of Paper 2, Kwong says you’re likely to find a question on the haber process, the reasons for optimum conditions, and the manufacture of chlorine bleach by electrolysis of brine. For the topic “Analytical Chemistry”, he advises brushing up on colorimetry, finding concentration from absorbance, and liquid-liquid extraction.
For now, since time is running out, Kwong suggests students go through the HKDSE Chemistry past papers, particularly the ones in 2013 and 2016. Here are some of the questions that he saw a high change of reappearing in this year’s paper:
2013 Paper 1 Question 1: distillation principle for the separation of H2O from sea water
2013 Paper 1 Question 2: molecular shape of NH3, BF3, dative covalent bond in H3N -> BF3
2013 Paper 1 Question 4: titration of weak dibasic acid with standard NaOH using phenolphthalein
2013 Paper 1 Question 12 and 2014 Paper 1 Question 13: calculation of equilibrium constant of gaseous reactant/product, e.g. 2NO(g) + O2(g) <=> 2NO2(g) or PCl3(g) + Cl2(g) <=> PCl5(g)
2015 Paper 1 Question 5: experiment to show NH3 is a weaker alkali than NaOH OR CH3COOH is a weaker acid than HCl/H2SO4
2016 Paper 1 Question 3: cracking experiment
2016 Paper 1 Question 5: predict the structure of monomer from an addition polymer, show the presence of C=C in the monomer by Br2
2016 Paper 1 Question 7: enthalpy cycle to find standard enthalpy change of formation of MgCO3/CaCO3/ZnO/Al2O3 using solid and acid
2016 Paper 1 Question 14: variation of electrical conductivity of elements
Edited by Charlotte Ames-Ettridge