Methyl Orange

In March 2014, the Australian Competition and Consumer Commission (ACCC) prompted the recall of some clothing for having unacceptable concentrations of particular azo dyes.

Azo dyes are organic (carbon) compounds with the general formula R-N=N-R' and are named after their unusual N=N, azo, functional group.

They are synthetic dyes used to colour foods, cosmetics, carpets, clothes, leather and textiles.

The azo dye that most Chemistry students will be familiar with is methyl orange, an acid-base.

Read more in the September 2014 issue of AUS-e-NEWS for the chemistry of Methyl Orange

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Ammonium Nitrate Explodes

On Friday 6^th September 2014, a truck carrying 56 tonnes of ammonium nitrate exploded after rolling over near a bridge on the Mitchell Highway between Cunnamulla and Charleville in the Australian State of Queensland. Eight people were injured, and the Mitchell Highway has been closed "indefinitely".

The most important use for ammonium nitrate is as a fertilizer, but it can also be used as an explosive. An explosion results when ammonium nitrate is brought into contact with heat, a source of ignition such as a spark, or, with reducing agents. Unfortunately, explosions of ammonium nitrate are not rare. A massive explosion of ammonium nitrate on 17^th April 2013 resulted in the death of 15 people, and the destruction of the West Fertilizer Company storage and distribution facility in Texas, USA.

Ammonium nitrate can be produced in commercial quantities by reacting ammonia gas with  nitric acid.

Reference: 
http://www.brisbanetimes.com.au/queensland/truck-explosion-injures-eight-closes-mitchell-highway-20140906-10dam3.html

Further Reading
Naming Ionic Compounds 
Writing Ionic Formula 
Mole Definitions 
Molar Gas Volumes

Suggested Study Questions:

1. Write the chemical formula for ammonium nitrate 
2. Explain why this compound is considered to be an ionic compound.
3. Write a word equation for the reaction between ammonia gas and nitric acid to produce ammonium nitrate
4. Write a balanced chemical equation for the reaction in question 3.
5. Ammonium nitrate decomposes in to N₂O and H₂O when heated. Write a balanced chemical equation for this reaction.
6. Calculate the molar mass of ammonium nitrate.
7. Calculate the moles of ammonium nitrate present in the truck.
8. Assuming that the decomposition of ammonium nitrate results only in gaseous products, what volume of gas at 25^oC and 100 kPa would be released by ammonium nitrate in the truck?
9. Assume the truck could carry a load with a volume of 30,000 L. Can you suggest a reason why rapidly decomposing ammonium nitrate could explode, destroying the truck, the bridge and the road?

Indicators and End Points

What colour is an indicator at the end point ?
At what pH does an indicator change colour?
Why is the colour change for an indicator always given as a range of pH values?

These questions are all addressed in AUS-e-TUTE's new Indicator End Point resources.
Read the tutorial, play the game, do the test and view worked solutions for the questions.

Not an AUS-e-TUTE Member?
There is currently a free-to-view tutorial available at http://ausetute.com.au/endpoint.html

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Sulfuric Acid - Sodium Hydroxide Titrations

Why does a titration of sulfuric acid using sodium hydroxide have only one equivalence point?
Why isn't the pH 7 at the equivalence point?

These are both excellent questions.

So, we've written a set of resources to help you understand!

AUS-e-TUTE Members should log-in and go to the new tutorial at:
http://www.ausetute.com.au/members/titrh2so4.html
and you can follow the links to the game and test from this page.

Not an AUS-e-TUTE member?
Part of this tutorial is currently available free to non-members for evaluation purposes at
http://ausetute.com.au/titrh2so4.html

Calculating the pH of Sulfuric Acid

How do you calculate the pH of a strong diprotic acid, that is, how do you calculate the pH of sulfuric acid?
I'm glad you asked!
AUS-e-TUTE has just added a new set of resources designed to help you answer this question.

AUS-e-TUTE Members should log-in and go to the links for the Polyprotic Strong Acids tutorial, game and test, on the Test Centre homepage, or, alternatively, go to your AUS-e-TUTE syllabus study guide and follow the links from that.

Not a member?
There is a "free-to-view" tutorial currently available for evaluation purposes at
http://www.ausetute.com.au/polyproticsacid.html

Titration Techniques

What piece of glassware should you use to make a standard solution?
What should you rinse a burette with before filling it with solution?
Should you force all the solution out of a pipette when you use it?

These and many other questions about Titration Techniques have been addressed in AUS-e-TUTE's new tutorials, games, tests, and exams.

Members should log in to use all these new resources which are listed under Volumetric Analaysis, or, use the links from your Syllabus Study Guide in the Members Only Test Centre.

A "free-to-view" tutorial on titration techniques is currently available for evaluation purposes for non-members: http://ausetute.com.au/titrtech.html

DOSS and Oil Spills

The molecular formula for dioctyl sodium sulfosuccinate, DOSS, is shown on the right. This is the anionic detergent molecule that was used to disperse the oil from the Deepwater Horizon spill in the Gulf of Mexico in 2010. When applied to an oil spill, DOSS decreases the size of oil droplete and prevents large oil slicks from forming.
BP applied about 1.84 million gallons of DOSS to the 210 million gallons of oil that is estimated to have gushed out of the oil well.
At the time it was believed that DOSS degraded rapidly in the environment so that it would not harm the marine environment.

Recent studies, however,  have shown that DOSS persists in the environment for much longer than was previously thought. Four years after the Gulf oil spill, DOSS remains present in deep-sea sediments and corals and in sand patties on Gulf beaches. mean for marine life or for the people who frequent the beaches? Scientists do not yet know what this might mean for marine life or for the people who frequent the beaches so some Gulf beaches have signs to warn people not to touch the sand patties.

Reference:
Helen K. White, Shelby L. Lyons, Sarah J. Harrison, David M. Findley, Yina Liu, Elizabeth B. Kujawinski. Long-Term Persistence of Dispersants following the Deepwater Horizon Oil Spill. Environmental Science & Technology Letters, 2014; 1 (7): 295 DOI: 10.1021/ez500168r

Further Reading:
http://www.ausetute.com.au/members/detergent.html (detergent tutorial for members)
http://www.ausetute.com.au/members/soaps.html (soaps tutorial for members)
http://www.ausetute.com.au/members/molecularformula.html (molecular formula tutorial for members)
http://www.ausetute.com.au/members/structural2D.html  (2-dimensional structural formula tutorial for members)
http://www.ausetute.com.au/members/condensedsf.html (Condensed structural formula tutorial for members)
http://www.ausetute.com.au/members/skeletal.html (Skeletal formula tutorial for members) 

Suggested Study Questions:

1.  Explain why dioctyl sodium sulfosuccinate, DOSS, is an anionic detergent molecule.
2. Give the name for the type of formula shown for dioctyl sodium sulfosuccinate, DOSS, in the article
3. Identify the functional groups found on a dioctyl sodium sulfosuccinate, DOSS, molecule.
4. Identify areas of the dioctyl sodium sulfosuccinate, DOSS, molecule that are:
   • hydrophilic
   • hydrophobic
5. Explain how the dioctyl sodium sulfosuccinate, DOSS, molecule might dissolve in water.
6. Explain how the dioctyl sodium sulfosuccinate, DOSS, molecule might dissolve in oil.
7. Explain how dioctyl sodium sulfosuccinate, DOSS, molecules might help break an oil spoil up into smaller oil droplets.
8. Write a complete 2-dimensional structural formula for dioctyl sodium sulfosuccinate, DOSS.
9. Write a condensed structural formula for dioctyl sodium sulfosuccinate, DOSS.
10. Write the molecular formula for dioctyl sodium sulfosuccinate, DOSS.