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

Monoprotic acid pH with a concentration of 0.022M

Question: What is the pH of a monoprotic acid with a concentration of 0.022 M?

Answer:
1. Assume this is a strong monoprotic acid so that it fully dissociates: HA → H⁺ + A^-

2. [HA] = [H⁺] = 0.022 M

3. pH = -log₁₀[H⁺] = -log₁₀[0.022] = 1.7

Find out more, and see questions with worked solutions, at https://www.ausetute.com.au/phstronga.html

What is the weight/volume percent (w/v) of a solution prepared from 50 g NaCl and 2.5 L of water?

Question: What is the concentration, weight/volume percent (w/v), of a solution prepared from 50. g NaCl and 2.5 L of water?

Answer:
1. w/v % is a measure of the concentration of a solution.
Units are often given as g solute/100 mL solvent.

2. w/v% = (mass solute in grams/volume of solution in mL) × 100

3. w= mass solute = 50 g
v = volume of solution = 2.5 L = 2.5 L × 1000 mL/L = 2500 mL (assuming the NaCl does NOT increase the volume as it dissolves in the water)

4. w/v% = (50 g/2500 mL) × 100 = 2 g/100 mL

Find out more, and see worked solutions to questions, at https://www.ausetute.com.au/wtvol.html

Why is the heat of formation for gaseous oxygen equal to 0?

Question: Why is the heat of formation for gaseous oxygen equal to 0?

Answer:
1. The standard heat of formation of any compound is defined as the enthalpy change for the compound when it is formed from its elements in their standard states.

2. Gaseous oxygen (O_2(g)) is a molecule (not a compound). The standard state for oxygen is as a gas, O_2(g).

3. There is no need to change gaseous oxygen, O_2(g) into its standard state because that is how it exists under standard conditions, therefore its heat of formation is 0.

Find out more at, and see worked examples, at https://www.ausetute.com.au/heatform.html

How to know what species will spontaneously react in redox reactions

A redox reaction is spontaneous if the standard electrode potential is positive,
that is,
if E^o_(reaction) > 0

Find out more, and look at a worked example, at: https://www.ausetute.com.au/redoxspon.html

Why is polyvinyl chloride an addition polymer?

Question: Why is polyvinyl chloride an addition polymer?

Answer:

1. An addition polymer is produced in an addition polymerization reaction.

2. In an addition polymerization reaction, the double bonds (C=C) in the monomer molecules open up so that one monomer molecule can "add on to" another monomer molecule to make a longer chain resulting in a polymer.

3. When vinyl chloride monomers (chloroethene monomers, CH₂=CHCl) join together in an addition polymerization reaction the polymer product is polyvinyl chloride, -(-CH₂-CHCl-)_n-

Find out more about addition polymerisation at https://www.ausetute.com.au/polymers.html

Find out more about polyvinyl chloride at  https://www.ausetute.com.au/pvc.html

Equilibrium Constants are Affected by Temperature Changes

Question:
How would the value of the equilibrium constant, k, be affected if the reaction was heated by 1000°c?
(a) if the reaction was endothermic
(b) if the reaction was exothermic

Answer:
(a)  For an endothermic reaction, an increase in temperature will increase the value of the equilibrium constant.
(b) For an exothermic reaction, an increase in temperature will decrease the value of the equilibrium constant.

Explanation: 

Go to https://www.ausetute.com.au/ktemperature.html for the tutorial. 

AUS-e-TUTE Members should log-in to use the game, test and exam with worked solutions on this topic.

Problem Solving in Chemistry

Some years ago, AUS-e-TUTE added a "how to solve problems in chemistry" page.
We call this approach to problem solving the StoPGoPS method:

1. Stop: State the question.
2. Pause: Prepare a plan of how you will solve the problem'
3. Go! Follow the steps in your plan.
4. Pause: Ponder the plausibility of your answer. (Have you answered the question you were asked? Does the answer look "about right"?
5. Stop: State your solution (if your answer seems plausible) or Start again (if your answer doesn't look right)

Well, we have now added a Template that students can use to help guide them through the Problem Solving Process. You can download this "Template for Problem Solving" pdf at ausetute.com.au for free.

Alkanols vs Alkanals

Question: Differentiate between alkanols and alkanals.

Answer: Alkanols and alkanals are both organic (carbon containing) compounds but they have different functional groups.
Alkanols contain the OH (hydroxyl) functional group.
Alkanals contain the C=O (carbonyl) functional group on a terminal (end) carbon atom of the carbon chain.
Because they have different functional groups they undergo different chemical reactions and will have different physical properties.
The physical and chemical properties of alkanols, for example, can be found at AUS-e-TUTE's page on Properties of Alkanols.

Number of elements in period 2

Question: Give the number of elements in period 2 of the periodic table
Answer: 8

The rows going from left to right across the Periodic Table are called Periods.
The periods are numbered from 1 at the top to 7 on the bottom.
The first period contains only 2 elements: hydrogen and helium.
The second period contains 8 elements: lithium, beryllium, boron, carbon, nitrogen, oxygen,  fluorine and neon.

Find out more about how the periodic table is arranged at http://www.ausetute.com.au/pertable.html

Find more about the elements making up Period 2 at http://www.ausetute.com.au/trendpd2.html

Which of the following is an acid-base indicator?

Question: Which of the following is an acid-base indicator?

1. hydrochloric acid 
2. sodium hydroxide 
3. water 
4. phenolphthalein

Answer: Phenolphthalein is an acid-base indicator

1. Hydrochloric acid is an acid
2. Sodium Hydroxide is a base
3. Water is neutral

60 Second Chemistry Quiz Challenge

Over the past few years AUS-e-TUTE has received a lot of feedback.
One of the things that we hear a lot from teachers who are part of an AUS-e-TUTE Class or School Group Membership is that the students love to do the drills. They love to see how many questions they can get done quickly.
Well ..... we thought we could turn some basic chemistry concepts into timed challenges.
And ..... we've just uploaded the very first of these. We've called it the 60 Second Chemistry Quiz Challenge because you have just 60 seconds to answer as many questions correctly as you can.
This 60 Second Chemistry Quiz Challenge is called "It's Elementary", so I'm sure you can already guess what the questions are about :)

You can have a go yourself at:
http://www.ausetute.com.au/challenge.html

and let us know what you think by emailing us at

6 Random Questions Answered

Every so often, AUS-e-TUTE randomly selects 6 questions that have been asked in the last few hours by people who are not AUS-e-TUTE members.
Today's selection is:

1/ Question from Canada, "ammonia gas undergoes a combustion to produce nitrogen dioxide gas and water vapour. write and balance the equation"

Answer: 2NH₃ +⁷/₂O₂ → 2NO₂ + 3H₂O

2/ Question from USA, "How do you convert weight percent to mass fraction?"

Answer:  percent by mass (weight) = mass (weight) fraction x 100
 reference: http://www.ausetute.com.au/weightpc.html

3/ Question from USA, "what are the physical properties of metals due to metallic bonding?"
Answer:  The physical properties of solid metals are:

• conduct heat
• conduct electricity
• generally high melting and boiling points
• strong
• malleable (can be hammered or pressed out of shape without breaking)
• ductile (able to be drawn into a wire)
• metallic lustre
• opaque (reflect light)

Reference: http://www.ausetute.com.au/metallic.html

4/ Question from USA, "Can air be separated by physical means?"
Answer: Yes. Air is a mixture so it can be separated by physical means.
Reference: http://www.ausetute.com.au/chemphys.html

5/ Question from USA, "How do you calculate atomic mass from relative abundance?"
Answer: Given the relative atomic mass (r.a.m.) of an element and the mass of each of its isotopes, the relative abundance of each isotope can be calculated:
let y/100 = abundance of isotope 1
and (100 - y)/100 = abundance of isotope 2
then, r.a.m = [y/100 x mass isotope 1] + [(100 - y)/100 x mass isotope 2]
and solve for y
Reference: http://www.ausetute.com.au/atomicmass.html

6/ Question from USA, "How do you turn empirical formula into molecular formula?"
Answer: molecular formula = whole number x empirical formula
Reference: http://www.ausetute.com.au/empirical.html

6 Random Questions Answered

1/ Question From USA, "How do you calculate density for chemistry?"
Answer: density = mass/volume
(http://ausetute.com.au/density.html)

2/ Question from Canada, "What is the main functional group in aspirin?"
Answer: Aspirin (acetylsalicylic acid) contains a carboxyl and an ester functional group. The carboxyl group is responsible for the acidic properties of aspirin.
(http://ausetute.com.au/aspirin.html)

3/ Question from USA, "What is the magnetic quantum number for iron?"
Answer: Magnetic quantum number, m_l,  has a value from -l to +l
For iron (Z=26), m_l can have values of -2, -1, 0, +1, +2
(http://ausetute.com.au/quantum.html )

4/ Question from Australia, "What is the enthalpy of combustion of ethanol?"
Answer: 1367 kJ/mol
(http://ausetute.com.au/members/alkanolp.html)

5/ Question from Australia, "What is enthalpy of combustion?"
Answer: Enthalpy (or heat) of combustion of a substance is the amount of energy released when 1 mole of the substance combusts (burns) in excess oxygen at constant pressure.
(http://ausetute.com.au/members/heatcomb.html)

6/ Question from Australia, "How do you tell a non reducing sugar?"
Answer: Reducing sugars can be oxidised by mild oxidising agents, non-reducing sugars can not be oxidised by mild oxidising agents.
(http://ausetute.com.au/members/redsugar.html)

6 Random Questions Answered

If you are an AUS-e-TUTE member you can just ask us a question and we'll do our best to answer it in a meaningful way, but, if you are not an AUS-e-TUTE member you'll have to resort to asking a search engine, and if you are lucky, we might answer your question here (if you have encrypted your search, for example if you are logged into a gmail account when you search google, we can't answer your question here).

Question from USA, "a substance that cannot be separated into simpler substances by physical or chemical mean is an it a mixture"
Answer from ausetute.com.au Yes, a substance that cannot be separated into simpler substances by physical means is a pure substance and not a mixture. If the pure substance can be separated by chemical means, then it is a compound and not an element.
Reference: http://ausetute.com.au/puresubs.html
http://ausetute.com.au/elements.html

Question from USA, "what is the density of a substance with a mass of 47.2 g and a volumn of 36 mL ?"
Answer from ausetute.com.au density = mass(g)/volume(mL) = 47.2/36 = 1.31g/mL
Reference: http://ausetute.com.au/density.html

Search from Canada, "what are some princeples of pure substance and mixturs"
Reply from ausetute.com.au "Mixtures can be separated by physical means. Pure substances cannnot be separated into their component parts using physical means"
Reference: http://ausetute.com.au/puresubs.html

Search from Malaysia, "why stable compound release less energy"
Reply from ausetute.com.au "Breaking bonds requires energy, making bonds releases energy. The more energy that is required to break the bonds, the more stable the compound will be."
Reference: http://ausetute.com.au/members/heatbond.html

Search from USA, "density of elements between 3.0g/ml and 6.0g/ml"
You can look these up for yourself here http://www.ausetute.com.au/members/ptablei.html

Search from USA, " electron neon orbitals"
Response from ausetute.com.au Do you want the set of orbitals (s and p orbitals) or the electron configuration of neon (1s² 2s² 2p⁶)?
Reference: http://www.ausetute.com.au/econfig.html