Monthly Archives: October 2015

8-Page VCE Chemistry Formula Booklet Just $55

VCE Chemistry Formula Booklet INSIDE
VCE Chemistry Formula Booklet, $55. Free, Fast Delivery Included.

Inspired by the formula booklets used by VCE Physics and VCE Maths Methods, here’s an 8-page Chemistry formula booklet you can use for your Year 11 and 12 Chemistry assignments. This custom-made booklet is a a collection of reliable formulae that I have been using to answer VCE Chemistry questions while teaching and tutoring.

There are 76 formulae in total, at least 10 of which are original. Orders are shipped on A3 paper, stapled along the spine and folded to an A4-sized booklet that resembles the VCAA Data Booklet.

Orders from schools, students and tutors are all welcome. Price includes free international delivery and 10% voucher for the T-shirt store.

Order your copy now by clicking here

VCE Chemistry Formula Booklet FRONT
Click to purchase a printed copy for just $55

Revise What’s HARD: Focus on Electrolysis

VCAA VCE Chemistry how difficult is each topic
Click to download PDF version. Numbers in parentheses denote Chapter numbers.

The VCE Chemistry examination is only 22 days away. As you complete at least one practice paper each day and correct them ccording to your revision timetable, you’ll be finding that you’ve already mastered certain topics while others remain difficult.

Patterns emerge in student readiness: each year, electrolysis is the worst-studied topic on the course. Because VCAA has a reputation for asking questions on topics that students repeatedly got wrong in previous years; I decided to test this hypothesis by getting real data from recent examination reports and displaying it on a scatterplot of:

  • how difficult each topic is (% of marks lost) on the x-axis
  • how often the topic is asked (marks per paper) on the y-axis

The results were fascinating. While it’s impossible to say with any certainty which topics will be on the examination this year, previous years’ examination papers have placed more emphasis on the difficult topics (electrolysis, Ka, redox and biofuels). Focus your revision on these topics again this year.

Conclusion: Focus your Chemistry revision this week on your least favourite topics… those topics will probably be worth more marks in the examination!

Chapter 25: Essential Calorimetry Formulae

Chapter 25 Essential Calorimetry Formulae VCE Chemistry
Click to download PDF version

Calorimetry can be a confusing topic. Avoid common errors by following these essential tips:

  1. Always label the units of E (kJ or J) above the E. This is the most common source of error in calorimetry calculations. Try this quick way to remember the required units of E: If there’s ΔH in the equation, the units are kJ; otherwise, the units are J.
  2. In E=mcΔT, all the variables refer to the mass of water being heated. A common error among students is to use the mass of limiting reactant instead of the mass of water. Generally, m in this equation is 100 g or a similar round number.
  3. Never convert ΔT to kelvin. Temperature changes are the same in kelvin and celcius… never add 273 when finding ΔT.
  4. No calibration step? Use m×c instead. Because E=mcΔT and E=CfΔT, it therefore follows that Cf ≡ m×c. For example, if we’re heating a 100.0 g of water without a Cf, we should use Cf = 100×4.18 = 418 J K-1 instead.
  5. In ΔH = E/n, n denotes the number of moles of limiting reactant. Never add up the number of moles of reactants: use the number of moles of limiting reagent only.
  6. Calculate twice. Students most often make mistakes when converting hours or days into seconds. Many answers are therefore wrong by a factor of 60. Do your calculations twice: once while doing the question and again when you check over your answers at the end of the SAC or examination.
  7. Know a ballpark figure. Neutralisation and solubility reactions tend to have 2-digit ΔH values; combustion reactions tend to have a 3-digit ΔH and explosive reactions tend to have a 4-digit  ΔH. If you get a 5-digit ΔH value, you’ve probably forgotten to convert your answer into kilojoules!
  8. Remember the ‘+’ or ‘-‘ sign! The calculator doesn’t know whether the answer should be positive or negative. Think about it yourself instead: endothermic reactions need a ‘+’ sign and exothermic need a ‘-‘ sign. VCAA awards a whole mark for getting the ‘+’ or ‘-‘ sign correct! It’s possibly the easiest mark in the whole paper.

Consider getting a home tutor who can answer your questions and explain difficult concepts to you. Students learn much faster with a tutor than on their own.

For more Study Tools for Year 12 students, click here.

Chapter 27/28: Six Universal Principles of Redox Reactions

Redox can be a confusing topic for VCE Chemistry students. It’s also taught right at the end of the year, when students are tired and some teachers are rushing their lessons so they can finish the course before the end of Term 3. Student motivation levels are at their lowest time of the year, which means that students often finish the course with an incomplete understanding of Redox.

Fortunately, there are six universal principles that are always true in Redox no matter what type of cell is being studied.

First, here’s a reminder of the types of cells you need to have studied in this course.

Galvanic Cells

  • Primary (can’t be recharged)
  • Secondary (can be recharged)
  • Fuel Cells (reactants are supplied continuously)

Electrolytic Cells

  • Electroplating Cells (no overall reaction)
  • Electrolytic Cells (non-spontaneous reaction)
  • Commercial Cells (usually molten electrolytes)
  • Recharge reaction of a secondary cell (non-spontaneous)

Now, here are the six universal Redox principles.

1. The strongest oxidant at the cathode reacts with the strongest reductant at the anode (SOC SRA)

To predict which species will react with each other, circle all the species present at the cathode on the electrochemical series. The highest species on the left will always react. Now, circle all the species present at the anode… the lowest species on the right will react.

2. The half-reaction with the highest E° value is always positive

In all cells, the half-equation with the highest electrode potential (also called ‘reduction potential’ or E° value) always occurs at the positive electrode. Similarly, the half-equation with the lowest electrode potential (E°) will always occurs at the negative electrode.

3. OIL RIG

Oxidation is loss of electrons. Reduction is gain of electrons.

4. ←AN OIL RIG CAT→

Anode reaction (oxidation reaction) is whichever reaction is happening to the left in the electrochemical series.

Cathode reaction (reduction reaction) is whichever reaction is happening to the right in the electrochemical series.

5. Electrons always flow in this order (RACO)

Reductant → anode → cathode → oxidant

6. In the internal circuit, cations always flow to the cathode, and anions always flow to the anode.

The internal circuit might be an electrolyte or a salt bridge that contains soluble weak oxidants and reductants such as KNO3(aq) (potassium nitrate). Either way:

  • cations always flow to the cathode; and
  • anions always flow to the anode.

Keep practicing redox questions by completing past papers, Checkpoints and Lisachem questions. If you need more help, contact me via the Get a Tutor button in the site’s menu bar. Students learn much faster with a tutor than on their own.

For more Study Tools for Year 12 students, click here.

Image courtesy of Annenberg Learner