Tips for your Final HSC Chemistry Exam PDF

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Tips to ace final HSC Chemistry...

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Examiners’ comments consistently reveal that the majority of lost marks are from basic errors: missing fundamental information (i.e. easy marks), incorrect balancing of chemical equations, forgetting states of matter, illegible or missing working, rounding errors and poorly drawn structures or apparatus. 1. Unpacking the question Effectively unpacking the question will give you a way to approach the question and get you marks for showing that you know which types of information are contained in the question.

1. Significant figures Significant figures are also crucial. A good rule of thumb is to use the least number of significant figures provided in the question. (I always use 5 s.f. throughout and round off at the end of the calculation). Be wary of significant figures and pH. Because pH is a logarithmic scale, only digits after the decimal place of a pH value are significant. For example, pH = 12.56 has only two significant figures.

2. Long response questions Certain words like “evaluate”, “compare” and “justify” have specific connotations and you should be aware of the meanings as decreed by your state’s curriculum authority. It’s imperative that you tie points together. Pretend you’re explaining something complex to a younger sibling: break it up into its component parts. During the reading time, think about where marks are allocated. You will always get at least one mark for a relevant (balanced) chemical equation and at least one mark for a valid rationalisation/effect of the equation. Memorise key phrases like “boiling point is a measure of the strength of intermolecular forces” or “strong acids completely ionise therefore the concentration of hydronium ions is equal to the concentration of the acid”.

3. Procedure questions

When certain questions ask you to “outline a procedure to…”, it is critical that you specify correct equipment and use realistic quantities of reagents. For example, in the test for the presence of unsaturation, bromine water must be the limiting reagent, so 2 mL of bromine water could be added to 10 mL of alkane/alkene, but not vice versa. You should also address any safety issues associated with a procedure with appropriate precautions.

4. Specific types of questions You will always have a Chemistry exam which assesses mandatory outcomes. It’s important to quickly recognise certain types of questions, like “Why pH” questions or “Le Chatelier’s Principle” questions. For example, if you’re ever asked why something is acidic (or basic), you must provide a hydrolysis reaction producing hydronium (or hydroxide) ions. Another common example is questions that ask why the pH is high or low. In these cases you need to provide a definition for pH which relates the hydronium ion concentration to the high (or low) pH value. Remember: your younger sibling doesn’t know why high [H3O+] results in low pH, and neither does the examiner know that you know it!

5. Presentation of diagrams Use a pencil and a ruler to draw diagrams. Two-dimensional (profile) diagrams are best. When drawing equipment that is open to the environment, or connected to other flasks, do not draw lines, which might imply they are sealed. 6. Structural diagrams You will have to draw some organic compounds in your Chemistry exam. It’s imperative that you draw all the atoms (yes, even the hydrogens). It’s easy (during exam prep) to omit less important atoms when drawing structures, but there’s usually a mark awarded for the presence of every atom in a compound. Covalent bonds must point toward the atoms they are bonded to. Don’t offend your marker with floating methyl groups or incorrectly ordered hydroxyl groups — you will lose marks:

For organic reactions using expanded structural formulae, balancing is less important. Usually marks are awarded for the correct structure of a reactant/product rather than correct balancing. For example, an acceptable answer for the oxidation of butan-2-ol could look like this:...