Saturday, October 31, 2020

How to study for Chemistry exams

As your chemistry exam gets closer, I'm sure you've been "studying" hard, probably reading through your notes, making summaries, summarizing the summaries, putting important concepts on flash cards... and a whole lot more. But will any of that help you achieve a good result on a chemistry exam?

Probably not. So, put your notes away and read on.

Chemistry examiners are not interested in whether you have memorized the "facts" (definitions, formulae etc). It is most unlikely that the following question will appear on a chemistry exam paper,

Question 1: "State Le Chatelier's Principle"

Chemistry examiners are interested in how you apply chemical principles to solve problems. So the following question is much more likely to be found on a chemistry exam paper,

Question 2: "A student dissolves some solid FeSCN2+ in water in a test tube at room temperature and pressure, producing a mixture of reddish-brown FeSCN2+(aq), pale yellow Fe3+(aq), and colourless SCN-(aq). The student observes that the test tube feels cooler as the solute dissolves.

(a) Write an equation to describe the process.

(b) Describe what colour change, if any, would occur if the test tube was placed in an ice-bath. Explain your answer"

Question 2 is asking you to apply Le Chatelier's Principle to a given chemical process.

The best way to study for your chemistry exam is to answer a variety of questions. AUS-e-TUTE Members have access to thousands of problems (with worked solutions and tutorials if you need some help). If you are not an AUS-e-TUTE member you can often find books of problems for a given course, and you probably have access to "past papers". 

Here's another question you might like to try,

Question 3: One step in the Ostwald process for manufacturing nitric acid from ammonia involves the production of nitrogen dioxide as shown in the chemical equation below:

2NO(g) + O2(g) ⇋ 2NO2(g)

A 10.00 L reaction vessel initially contained 2.50 mol NO(g) and 1.20 mol O2(g).

0.50 mol NO(g) remained in the vessel after equilibrium was established.

(a) Calculate the equilibrium constant for this reaction.

(b) A second experiment was conducted using the same initial amounts of NO(g) and O2(g) but in a reaction vessel of about half the volume. What affect would this have on the value of the equilibrium constant? Explain your answer. 

If you find these questions a bit tricky, then AUS-e-TUTE might help you become more familiar with exam-type questions and how to answer them. Join AUS-e-TUTE today

Saturday, October 3, 2020

Brønsted-Lowry Theory of Acids and Bases

 Ammonia, NH3, is a base right?

Well, yes it is sometimes... but it can also be an acid.

Welcome to the wonderful world of Brønsted-Lowry acids and bases.

At AUS-e-TUTE, we've just added a new tutorial, game, tests and exam to help you understand Brønsted-Lowry acids, bases and their conjugates.

If you are not an AUS-e-TUTE Member you can view a tutorial on this subject for free at https://www.ausetute.com.au/bronstedlowry.html