Recovering Gold from e-Waste

 We use electronic devices every day; computers, drones, home security systems, mobile phones, smart speakers, smart watches, etc. If the device stops working, or we want to upgrade to a newer version, we throw away the old device resulting in electronic waste or e-waste. Each of these devices contains a printed circuit board (PCB) and the metal content of each PCB can be as high as 40% by mass. 

Recycling 1 tonne of mobile phones alone could produce more than 130 kg metal, including about 340 g of gold. The value of just the gold in that tonne of rubbish is over $25,000(AUD). Recovering metal from waste electronics and electrical equipment is becoming big business, but what impact does this have on us and our environment?

 Read this edition of AUS-e-NEWS to find out more ...

You can subscribe to AUS-e-NEWS, AUS-e-TUTE's free quarterly newsletter for chemistry students and teachers, at 

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Hydrogenation of Alkenes

How can you convert an unsaturated hydrocarbon such as an alkene, into a saturated hydrocarbon (an alkane)?
With the magic of chemistry (a catalyst), you can add hydrogen across the double bond in an alkene!
AUS-e-TUTE has just added new resources to help our members understand this, and to practice answering test questions. Members should log-in to use these new resources.

If you are not an AUS-e-TUTE member, a "free-to-view" tutorial on this topic is currently available at https://www.ausetute.com.au/hydrogenation.html

Classification of Organic Reactions

Organic reactions are reactions in which the reactants and products are carbon-containing compounds, or organic compounds.
The chemical reactions that organic compounds take part in can be classified as:

• substitution reactions
• addition reactions
• elimination reactions
• oxidation reactions
• reduction reactions
• polymerisation reactions
• rearrangement reactions

AUS-e-TUTE has just added new resources including  a tutorial, game and test with worked solutions to help you identify and classify these types of organic reactions. AUS-e-TUTE Members should log-in to use these new resources.

If you are not an AUS-e-TUTE, a free-to-view tutorial is currently available at https://www.ausetute.com.au/organicrxn.html

Properties of Aldehydes and Ketones

Aldehydes and ketones contain the same functional group, for example, butanal and butanone both contain the same carbonyl functional group (C=O). So how would you tell if a substance was butanal or butanone?
AUS-e-TUTE has just added new resources to help you understand the similarities and differences in the chemical and physical properties of aldehydes and ketones (as represented by alkanals and alkanones). AUS-e-TUTE Members should log-in to use the new tutorial, game, test and exam with worked solutions.
If you are not an AUS-e-TUTE member there is currently a "free-to-view" tutorial on this topic at https://www.ausetute.com.au/ketones.html

How to write half-equations for aqueous solutions under basic conditions

Lots of common batteries like alkaline batteries and NiCad batteries use oxidation and reduction reactions in alkaline, or basic, conditions.
Learn how to write half-equations for these reactions at https://www.ausetute.com.au/halfeqtnb.html

AUS-e-TUTE Members should log-in to access the new tutorial, game and test with worked solutions to help you learn how to write these half-equations for basic conditions.

How to write half-equations for aqueous solutions under acidic conditions

Some batteries, like lead-acid batteries used in cars, and some fuel cells like those that use alcohols, rely on oxidation and reduction reactions that occur in aqueous solution under acidic conditions.
You will need to be able to write half-equations for these reactions.
How do you write balanced chemical half-equations for these reactions?

Go to https://www.ausetute.com.au/halfeqtn.html to find out!

AUS-e-TUTE Members should log-in to use the Members ONLY tutorial, game, test and exam (with worked solutions).

Lithium-ion batteries

When you walk around having a chat to your friends on your mobile phone, or watch a show on your tablet, or do your homework on your laptop in a cosy cafe, have you ever stopped to wonder about the amazing revolution in chemistry that allows you to do these "every day" things?

Batteries that are small, that can store enough electrical energy so that they can be used continuously for hours, can be quickly recharged, and can be discharged and recharged many, many times, are a very recent development. Without these batteries your life-style would be a lot less mobile!

What makes these batteries so special?

Find out in the December 2019 issue of AUS-e-NEWS

https://www.ausetute.com.au/ausenews.html

Queensland Nickel

In January 2016, Queensland Nickel went into voluntary administration, that is, the company was having difficulty meeting its financial obligations. The story's big news in Australia because Queensland Nickel is 100% owned by one of Australia's most colourful characters, Clive Palmer. Palmer is reputed to be worth about $1 billion and has business interests in minerals and property, including the Palmer Coolum Resort which houses animatronic dinosaurs on its golf course which has been rather controversial. Palmer has been involved in politics since the 1970s firstly as a member of the National Party, then of the Liberal-National Party, then in 2013 he formed his own political party, the Palmer United Party or PUP. And yes, Australians did actually vote PUPs into parliament, including Palmer himself who won the seat of Fairfax  (located in Queensland on the Sunshine Coast, just north of Brisbane, created in 1984 and named after the founder of the Country Women's Association, Ruth Fairfax). But enough of the Australian political history lesson, lets get back to the Queensland Nickel problem.

Nickel is an important metal in our society. More than 80% of the nickel produced worldwide goes into alloys. When alloyed with other metals, nickel imparts toughness, strength and resistance to corrosion as well as various magnetic, electrical and heat resistant properties.  About 65% of all nickel produced is consumed making stainless steel which is used to make cars as well as many other consumer and commercial products, including the kitchen sink!

The worlds largest producers of nickel are the Philippines, Indonesia, Russia, Canada and Australia.

Australia exports about $4 billion of nickel per year, making it an important export commodity. Australia has about 17 million tonnes of nickel reserves. Western Australia has about 96% of these reserves, Queensland about 3.8% and Tasmania about 0.2%. At the current rate of production, these reserves should last about 70 years.

In 1974, nickel mining began at Greenvale, 220 km northwest of Townsville. This nickel ore was transported by train to the Palmer owned refinery at Yabulu,  about 25 km north of Townsville. The Greenvale mine closed in 1992, however, commencing in 1986, nickel ore was shipped from New Caledonia, the Philippines and Indonesia to Townsville then transported by rail to the refinery. The refinery produces about 32,000 tonnes of nickel and 19,000 tonnes of cobalt per year.

The Yabulu plant carries out three process:

1. ore processing
2. mixed nickel-cobalt hydroxide processing
3. nickel and cobalt refining

Nickel ore contains nickel oxide, NiO. Ore processing involves blending, drying, and milling to fine powders.
The fine ore powder is then mixed with fuel oil reductant (C) and reduction roasted at  750°C under reducing conditions achieved by the partial combustion of fuel oil to carbon monoxide and the addition of hydrogen gas. We can represent the reduction of NiO by C as:
                750°C 
NiO + C  --->    Ni + CO

 The reduced ore, containing nickel and cobalt, is cooled and then leached in aqueous ammonium carbonate liquor at atmospheric pressure to selectively dissolve nickel and cobalt. This product liquor contains about 12 g L^-1 Ni and 0.6 g L^-1 Co, while the residual solids in the tailings contain carbonates of manganese and magnesium. The solution containing dissolved nickel and cobalt is separated from the solids and the excess ammonia removed. Patented ammoniacal extraction technology selectively extracts nickel which is then precipitated as basic nickel carbonate,  Ni₄CO₃(OH)₆(H₂O)₄

4 Ni²⁺ + CO₃²⁻ + 6 OH⁻ + 4 H₂O --->  Ni₄CO₃(OH)₆(H₂O)₄

This basic nickel carbonate is dewatered and the product can then be calcined in a rotary kiln under reducing conditions to produce nickel. Calcination drives off carbon dioxide and water to produce nickel calcine, approximately 60% nickel and 40% nickel oxide. After further reduction of nickel calcine using hydrogen, a metal is produced that is 99% nickel:
NiO + H₂  --->  Ni + H₂O
The Palmer-owned Queensland Nickel refinery is still operational, and there is no shortage of nickel ore to refine, so why is the business in danger of closing? 
According to Palmer, the financial difficulties Queensland Nickel find itself in result from a fall in nickel prices  and the Queensland Government's refusal to guarantee a $35 million loan. Certainly nickel prices have been in a general decline, In 2007, the price of nickel peaked at about $50,000 per tonne, in 2008 the price of nickel was about $20,000 per tonne, now it is worth less than half that much, probably because the supply of nickel is simply greater than demand for it. So, why is this story getting so much media attention? Is it because 237 workers at the refinery were sacked? Maybe, but the biggest issue in the media surrounds the purported donations made by the Palmer-owned Queensland Nickel to the Palmer-founded and led political party, PUP, to the tune of $15.2 million donated in 2013-14 financial year and another $5.9 million in 2014-15, which could probably have paid 237 workers for quite a few more months.

References:
http://www.abc.net.au/news/2016-01-16/qld-nickel-donated-nearly-$290k-just-2-weeks-before-sackings/7093096
http://www.smh.com.au/federal-politics/political-news/clive-palmers-political-career-on-the-brink-after-business-meltdown-20160118-gm8a0q.html
http://www.smh.com.au/business/mining-and-resources/clive-palmers-queensland-nickel-in-voluntary-administration-20160117-gm7x8r.html

Further Reading:
Metal Extraction Concepts: http://www.ausetute.com.au/metalextract.html
Carbon Reduction Method: http://www.ausetute.com.au/creduction.html
Redox Concepts: http://www.ausetute.com.au/redox.html
Oxidation States (Numbers): http://www.ausetute.com.au/oxistate.html
Percentage Composition: http://www.ausetute.com.au/percentc.html

Suggested Study Questions:

1. What is the oxidation state (oxidation number) of nickel in each of the following:
   • Ni
   • NiO
   • Ni₄CO₃(OH)₆(H₂O)₄


2. In the reaction:      NiO + C  --->   Ni + CO
   • Which species is oxidised?
   • Which species is reduced?
   • Which species is the oxidant?
   • Which species is the reductant?
   • Which species is the reducing agent?
   • Which species is the oxidising agent?
   • Is this a redox reaction? Explain your answer.
3. Nickel oxide, NiO, can also react with hydrogen gas in a similar reaction to the one above in order to produce solid nickel, Ni, and water.
   • Write a balanced chemical equation for this reaction.
   • Which species is oxidised?
   • Which species is reduced?
   • Which species is the oxidant?
   • Which species is the reductant?
   • Which species is the reducing agent?
   • Which species is the oxidising agent?
   • Is this a redox reaction? Explain your answer.
4. Nickel oxide, NiO, can also react with carbon monoxide gas in a similar reaction to the one above in order to produce solid nickel, Ni, and carbon dioxide.
   • Write a balanced chemical equation for this reaction.
   • Which species is oxidised?
   • Which species is reduced?
   • Which species is the oxidant?
   • Which species is the reductant?
   • Which species is the reducing agent?
   • Which species is the oxidising agent?
   • Is this a redox reaction? Explain your answer.
5. The carbon reduction method can also be used to extract zinc metal from zinc oxide.
   • Write a balanced chemical equation for this reaction.
   • Which species is oxidised?
   • Which species is reduced?
   • Which species is the oxidant?
   • Which species is the reductant?
   • Which species is the reducing agent?
   • Which species is the oxidising agent?
   • Is this a redox reaction? Explain your answer.
6. Name one other metal that could be extracted from its oxide using the carbon reduction method and explain why this method could be used for this metal.
7. Name a metal that cannot be extracted from its oxide using the carbon reduction method and explain why this method would not work.
8. Native nickel, that is, nickel found as the element and not in compounds, is rarely found in nature on Earth. Explain why.
9. When native nickel is found on Earth, it occurs as an alloy with iron inside large meteorites. Explain why elemental nickel can be found inside these meteorites that landed on Earth.
10. Calcination is the process of heating a compound to drive off carbon dioxide. Nickel(II) carbonate can be calcined to produce nickel(II) oxide. Write a balanced chemical equation for this reaction.
11. The most common application of  calcination is to convert calcium carbonate in limestone into calcium oxide (called lime) in the production of cement. Write a balanced chemical equation for the calcination of calcium carbonate.
12. Assume a nickel ore is composed of 2% NiO, what mass of ore must be processed annually to produce 32,000 tonnes of nickel metal?
13. In 2014 the price of nickel was an average of about $16,000 per tonne, while in 2015 its price had fallen to about $10,000 per tonne. Assuming Queensland Nickel maintained a steady production rate of 32,000 tonnes per year, what was the change in Queensland Nickel's revenue from 2014 to 2015.
14. What do you think contributed most to the financial difficulties of Queensland Nickel, falling nickel prices or millions of dollars in political donations? Justify your answer.

Sulfuric Acid and Sugar

November 28, 2014, The Canberra Times reported that, "Students were looking on as a teacher conducted an experiment involving sugar and sulfuric acid inside a cabinet when the glass container holding the acid exploded."
The experiment referred to is probably similar to the one shown in the YouTube video below in which concentrated sulfuric acid from a container is poured over sugar in a beaker.

Safety Notes

Sulfuric acid will cause permanent damage if it comes into contact with the eyes or skin. Concentrated solutions of sulfuric acid are extremely corrosive. When sulfuric acid is dissolved in water enough heat is released to make water boil! Carbon monoxide and carbon dioxide are both toxic gases. Sulfur dioxide gas is toxic in high concentration and is a severe respiratory irritant at lower concentration.Some people, especially those prone to asthma, may be especially sensitive to sulfur dioxide. In the presence of moisture, sulfur dioxide forms an acidic, corrosive solution, which in contact with the skin or eyes may lead to burns.

You will notice that the reaction seems to proceed slowly at first. The reaction mixture turns yellow as the reaction begins. This reaction releases heat, it is said to be an exothermic reaction. The heat produced by the reaction then speeds up the rate of further reactions, and, in the video, this is also accelerated by stirring the mixture.

Table sugar is made up sucrose, molecular formula C₁₂H₂₂O₁₁ and structural formula as shown below:

The reaction between sucrose and sulfuric acid in which solid carbon, water vapour and heat are produced is known as a dehydration reaction  :
C₁₂H₂₂O₁₁(s) → 12C(s) + 11H₂O(g)     ΔH = -918.9 kJ mol^-1 Since the enthalpy change for this reaction is negative, the reaction is exothermic, the reaction gives off heat.
Sulfuric acid molecules have a great affinity for water, that is, sulfuric acid will readily and spontaneously dissolve in water. The water produced by the dehydration of sucrose will then be used to dilute the sulfuric acid that is present. This reaction is also exothermic.
H₂SO₄(l) → H₂SO₄(aq)     ΔH = - kJ mol^-1 The heat produced by this reaction also speeds up the rate of the dehydration reaction and subsequent dilution reactions.
Solid carbon is black, so the "black snake" is just carbon.
But what causes the carbon to "rise up" out of the beaker? This must be the result of evolving gases forcing their way through the mixture as the reaction proceeds. The gases that have been identified as products of this reaction  are:

• carbon monoxide (CO) 66% of the dry gas volume (ie, water has been condensed out)
• carbon dioxide (CO₂) 17% of the dry gas volume
• sulfur dioxide (SO₂) 17% of the dry gas volume

Since sulfuric acid does not oxidize carbon, it is most unlikely that the carbon monoxide and carbon dioxide gases are the result of a reaction between the black snake carbon and sulfuric acid. It is much more reasonable to assume that some of the sucrose undergoes dehydration by the sulfuric acid while some this sucrose (and/or some of the resulting intermediate organic products) is oxidized by the sulfuric acid to produce carbon monoxide gas and carbon dioxide gas. During this process, the sulfuric acid will itself be reduced, resulting in the formation of sulfur dioxide gas.

Reference:
http://www.canberratimes.com.au/act-news/students-treated-after-spill-in-burgmann-anglican-school-sciencbe-laboratory-20141128-11vzad.html

Further Reading:
http://ausetute.com.au/safety.html
http://www.ausetute.com.au/mmcalcul.html  
http://www.ausetute.com.au/moledefs.html
http://www.ausetute.com.au/massmole.html
http://www.ausetute.com.au/concsols.html 
http://www.ausetute.com.au/molarvol.html
http://www.ausetute.com.au/molreact.html

Suggested Study Questions:

1.  Describe two hazards in the YouTube Video.
2.  Describe the safety precautions you would take to minimize the risk of the hazards identified in question 1 above.  
3.  Why do you think the concentrated sulfuric acid is added to the sugar rather than adding the sugar to the container of sulfuric acid?
4.  In a typical experiment, 25 mL of 18 mol L^-1 sulfuric acid is added to 50 g of granulated sugar (sucrose). Calculate the amount in moles of :
   • sucrose used
   • sulfuric acid used
5. Calculate the mass of carbon that could be produced in the typical experiment given in question 4.
6. What assumptions have you made in order to calculate the mass of carbon in question 5?
7. Assume that all 50 g of the sucrose is now oxidized at 25^oC to produce carbon dioxide gas and liquid water. What is the maximum volume of carbon dioxide gas, in litres, that could be produced?
8.  Predict what you think might happen if a 50 g of granulated sugar were quickly added to 25 mL of concentrated sulfuric acid in a 100 mL conical flask that was being swirled continuously.
9. Sucrose is a disaccharide, made up of the monosaccharide glucose and the monosaccharide fructose. Starch and cellulose are both polysaccharides, that is, they are made of repeating glucose monomer units. Predict what would happen if you spilled concentrated sulfuric acid on:
   • a paper cup (cellulose)
   • a piece of raw potato (starch)
   • a cotton shirt (cellulose)
10. Design an experiment that could safely be performed in the laboratory to test your predictions in question 9.
11. Do you think that concentrated sulfuric acid will react with the monosaccharide glucose? Explain your answer using a chemical equation.
12.  Design an experiment that could safely be performed in the laboratory to test your prediction in question 11.

Sulfur Cycle

Sulfur, an element found in proteins, is cycled through the Earth's atmosphere, oceans and land, and, as it does, it undergoes chemical changes.
Most of the sulfur found on Earth is found in seawater and in rocks, in particular sedimentary rocks like shales containing pyrite (iron(II) sulfide or iron disulfide) and  in evaporite rocks containing anhydrite (anhydrous calcium sulfate), baryte (barium sulfate) and gypsum (hydrated calcium sulfate). The amount of mobile sulfur is continuously increasing due its release during volcanic activity. Human activities such as the burning of fossil fuels including coal and natural gas are also increasing the amount of mobile sulfur on Earth because fossil fuels contain sulfur as an impurity.

The sulfur cycle can be represented by the following 4 steps:

1. The incorporation of sulfur from organic (carbon) compounds like proteins, into elemental sulfur and inorganic compounds such as hydrogen sulfide, and the sulfide minerals such as pyrite (iron pyrite or fool's gold).
2. Oxidation of hydrogen sulfide, elemental sulfur and inorganic sulfides into sulfate ions.
3. Reduction of sulfate ions to sulfide ions.
4. Incorporation of the sulfur from sulfide ions into organic compounds (including organic compounds that contain metal atoms), such as proteins.

The oxidation of sulfur (step 2 in the cycle above) plays a part in removing oxygen from the atmosphere by incorporating oxygen into sulfate ions. Scientists have thought for a long time that the contribution of the sulfur cycle in removing atmospheric oxygen  is not nearly as important as the role of the carbon cycle in removing atmospheric oxygen. New research is suggesting that the weathering of pyrite and its burial may be more important than originally thought in regards to regulating oxygen.

Reference:
Halevy, S. E. Peters, W. W. Fischer. Sulfate Burial Constraints on the Phanerozoic Sulfur Cycle. Science, 2012; 337 (6092): 331 DOI: 10.1126/science.1220224

Further Reading:
Writing Ionic Formulae
Naming and Writing Formulae for Covalent Compounds
Oxidation Number (oxidation state)
Writing Precipitation Reaction Equations
Balancing Molecular Equations
Oxidation and Reduction Concepts
Carbon Cycle

Suggested Study Questions:

1. Write the chemical formula for each of the following:
   • elemental sulfur
   • hydrogen sulfide
   • iron(II) sulfide (iron disulfide)
   • calcium sulfate
   • barium sulfate
   • sulfate ion
   • sulfide ion
2. Give the oxidation number (oxidation state) for sulfur in each of the following:
   • S₈
   • H₂S
   • CaSO₄
   • BaSO₄
   • CaSO₄.2H₂O
3. Seawater is an aqueous solution which contains ions such as, barium, calcium, and sulfate. As seawater evaporates, calcium sulfate and barium sulfate precipitate out of the solution. Write a balanced molecular equation for:
   • precipitation of barium sulfate from seawater
   • precipitation of calcium sulfate from seawater
4. Write balanced chemical equations for each of the following:
   • combustion of carbon in coal to form carbon dioxide
   • combustion of sulfur in coal to form sulfur dioxide
   • combustion of methane (natural gas) to form carbon dioxide
5. Consider this equation for the oxidation of elemental sulfur :
   2S + 2H₂O + 3O₂ → 2H₂SO₄
   • Determine the oxidation number (oxidation state) of sulfur in elemental sulfur and in H₂SO₄
   • Use this information to explain why this equation can be said to represent an oxidation of sulfur.
   • Identify a species that is being reduced. Explain why this species can be said to be undergoing reduction.
   • Explain why it is appropriate to refer to the equation above as a redox (oxidation-reduction) reaction
   • For the reaction given above give the formula for the oxidant (oxidizing agent) and for the reductant (reducing agent).

Invisible Ink

The CIA has declassified a number of documents from the first World War, some detailing the nature of invisible inks used at that time. These documents are available in the Freedom of Information Act Electronic Reading Room at cia.gov

One recipe for invisible ink was as follows
"A solution of nitrate of soda and starch in water may be carried for example in handkerchiefs or starched collars, starched shorts or anything else starched. These things being laid in this solution and then ironed. The article thus treated is later on again put in water and a solution obtained which can be used for invisible writing. The best means for developing are iodate of potassium."

And the recipe for developing the ink using potassium iodate
"Iodate of potassium, 5 grams with 100 grams of water, 2 g of tartaric acid added."

The beauty of this recipe for invisible ink is that the ingredients would be quite readily available to the spy.
Nitrate of soda (sodium nitrate) could be found in lawn fertilizers.
Iodate of potassium (potassium iodate) could be found in disinfectants.

As all science students know,
starch + iodine solution → blue-black iodine-starch complexBut a person carrying around a bottle of iodine solution may have been a bit suspicious during the war.
Potassium iodate can react with tartaric acid in aqueous solution to produce potassium iodide solution. The iodide ions released can react further with the iodate ions to produce aqueous iodine solution (I_2(aq)):
5I^-_(aq) + IO₃^-_(aq) + 6H⁺_(aq) → 3I_2(aq + 3H₂O_(l)


Reference
http://www.washingtonpost.com/world/cia-recipe-for-invisible-ink-among-newly-released-wwi-era-documents/2011/04/19/AFn5Ej7D_story.html
http://foia.cia.gov/CIAsOldest/Secret-writing-document-one.pdf
http://foia.cia.gov/CIAsOldest/Secret-writing-document-two.pdf
http://foia.cia.gov/CIAsOldest/Secret-writing-document-three.pdf
http://foia.cia.gov/CIAsOldest/Secret-writing-document-four.pdf
http://foia.cia.gov/CIAsOldest/Secret-writing-document-five.pdf
http://foia.cia.gov/CIAsOldest/Secret-writing-document-six.pdf

Further Reading
Naming Ionic Compounds
Writing Ionic Formula
Molecular Mass (Formula Weight)
Percentage Composition
Oxidation and Reduction
Oxidation States (numbers)

Study Questions:

1. Write the formula for each of the following
   
   • sodium nitrate
   • potassium iodide
     
   • potassium iodate
2. Calculate the molecular mass (formula weight) for each of the following:
   
   • sodium nitrate
   • potassium iodide
     
   • potassium iodate
3. Calculate the percentage composition of each of the following:
   
   • sodium nitrate
   • potassium iodide
     
   • potassium iodate
4. What is the oxidation state (oxidation number) of iodine in each of the following:
   
   • potassium iodide
     
   • potassium iodate
   • molecular iodine
5. In the reaction between iodide ions and iodate ions, which species are being
   • oxidized
   • reduced
6. Write half-reaction equations for each of the reactions below:
   
   • iodide → iodine
   • acidified iodate → iodine