Lesson 9 Reactions

  Introduction

B9.1 mobile phone charger

Countless chemical reactions are occurring in your body and all around you at all times, from cellular respiration occurring in your mitochondria to photosynthesis occurring in plant leaves to the battery in your phone.

In this lesson, you will look at some examples of chemical reactions that produce useful substances and energy.

  Targets

By the end of this lesson, you will be able to

• provide examples of household, commercial, and industrial processes that use chemical reactions to produce useful substances
  
• provide examples of household, commercial, and industrial processes that use chemical reactions to produce energy
  
• identify chemical reactions that are significant in society

  Watch This

6 Chemical Reactions that Changed History @ YouTube It’s Okay To Be Smart  

Watch this video. It goes over six chemical reactions that changed history. Keep in mind that the formation of an alloy is a physical change not a chemical change.  This will help get you in the right mindset for this lesson.

  Digging Deeper

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Here are some more details about the yummy Maillard reaction that was introduced to you in the video.

©http://www.compoundchem.com/2015/01/27/maillardreaction/
B9.1a A Guide to the Maillard Reaction

  Reactions that Produce Useful Substances

B9.2 Toasting marshmallows

There are an incredible number of chemical reactions that are essential to society. There are also many reactions that may not be essential, but certainly do improve the quality of your life. In this lesson, we will look at only a few examples.

Cooking

One of the most fundamental chemical reactions utilized every day in your home is cooking. The original purpose of cooking was to kill pathogens to make food safe to eat. In addition, the variety of food that was consumed greatly increased once cooking methods became wide spread. Cooking can also increase the flavour of food.

Photosynthesis

B9.3 Leaves in sunlight

Photosynthesis is an amazing process. Put simply, it is the key to life on Earth. It is a chemical reaction that converts simple substances—sunlight, carbon dioxide, and water—into food!

6CO₂(g) + 6H₂O(l) + sunlight → C₆H₁₂O₆(s) + 6O₂(g)

  Digging Deeper

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©CNRL
B9.4 The algae process

The Algae Project

Canada’s Oil Sands Innovation Alliance (COSIA) is working on creating a bioreactor that uses algae to convert carbon dioxide into biofuel and biomass products.

Baking Soda versus Baking Powder

B9.5 Baking

Both baking soda and baking powder are used in baking to produce carbon dioxide gas that will cause baked goods to rise. The difference between these two ingredients is that baking soda is a pure substance that needs an added reactant, specifically, an acid—such as vinegar, buttermilk, or yogurt—to activate it.

NaHCO₃(s) + H⁺(aq)→ Na⁺(aq) + CO₂(g) + H₂O(l)

Baking powder, however, is a mixture of two substances—a dry base and a dry acid— so it just needs to be moistened in order to activate the reaction.

NaHCO₃(aq) + KHC₄H₄O₆(aq) → KNaC₄H₄O₆(aq) + H₂O(l) + CO₂(g)

Splitting Water

Hydrogen has a bright future as a source of energy. When it is burned to produce power, it has little to no negative impact on the environment, unlike power produced by burning fossil fuels. Hydrogen gas can be readily produced by splitting water into its elements: hydrogen and oxygen.

2H₂O(l) + energy → 2H₂(g) + O₂(g)

On the down side, large amounts of electricity are needed to split water; so depending upon how that electricity is generated, hydrogen fuel may not be such a clean energy source. You will learn more about different energy sources in Unit C.

  Digging Deeper

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© Wikimedia Commons
B9.6 Testing for hydrogen gas

The splitting of water creates two colourless, odourless gases. How can each of them be identified? There are diagnostic tests that are easy to perform to confirm the identity of a gas. Watch this video to learn what these diagnostic tests entail.

 

Refining Silicon

B9.7 Silicon computer chip

Refining silicon is very important, as it is essential for the production of microchips. Silicon is readily available as sand, SiO₂, but it is tightly bound in that compound and thus sand needs to undergo a chemical reaction to liberate pure silicon. Silicon used in computer chips needs to be 99.9999999% pure. One of the reactions used to purify silicon is as follows:

SiO₂(s) + 2C(s) → Si(l) + 2CO(g)

Haber–Bosch Process

© Wikimedia Commons
B9.8 Haber-Bosch schematics

Ammonia is an essential compound that is used as a fertilizer, as a precursor in the production of explosives, as a precursor in the manufacture of other industrial chemicals, as a cleaning agent, as a refrigerant, and for many other uses.

Historically, the main source of reactant chemicals used to produce ammonia came from mining nitrate deposits. But these deposits were in limited supply; a new source was needed. Could ammonia be produced in the lab using a simple formation reaction?

N₂(g) + 3H₂(g) → 2NH₃(g)

An obvious source for the reactant nitrogen was the atmosphere, since the atmosphere is comprised of nearly 80% nitrogen gas. However, atmospheric N ₂ is exceptionally stable and will not readily react. Converting N₂ into ammonia posed a challenge for chemists. This challenge was solved by the work of German Chemists Fritz Haber and Carl Bosch. They created the Haber–Bosch process used to manufacture 160 million tonnes of ammonia annually.

  Did You Know?

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B9.9 Historical explosives

During World War I, the production of ammunitions required large amounts of nitrate. The Allies had access to large sodium nitrate deposits in Chile. Germany had no such resources, so the Haber–Bosch process proved essential to the German war effort. Synthetic ammonia from the Haber–Bosch process was used for the production of nitric acid, a precursor to the production of ammunition.

  Read This

  Practice Questions

1. Identify a chemical reaction that is occurring at this moment in close proximity to you.
   
   
   Check your work.
   

   Answers will vary; examples of chemical reactions that may be occurring around you are cellular respiration, photosynthesis (if there are any plants), combustion (if you have a furnace running), or a neutralization reaction (if you have eaten an antacid such as Tums). There are countless reactions that are occurring all around you. If you are in doubt as to whether or not the answer you came up with is appropriate, please contact your teacher.
   

  Reactions That Produce Energy

B9.10 Lithium ion battery pack

Not only do chemical reactions produce useful substances, but some chemical reactions are used to produce energy. Our society consumes energy at an unprecedented rate. Where does this energy come from? And what effects will this consumption have on our environment? You will delve into these questions more in Units C and D.

In this unit, you will look at four examples of chemical reactions used to produce energy.

Batteries

B9.11 Battery-powered devices

A portable source of energy is key to many activities in your daily life, such as using your laptop, driving a vehicle, operating your phone, or even controlling a heartbeat with a pacemaker.

There are several types of batteries that use a variety of chemical reactions. One such type of battery is the lithium ion battery found in your phone.

LiC₆(s) + CoO₂(s) → C₆(s) + LiCoO₂(s) + energy

While the disposal of lithium ion batteries is easier because they do not contain the toxic metals of lead or cadmium found in other batteries, there are still environmental concerns with the refining of the raw materials needed for the production of these batteries. And even though they do not contain the toxic chemicals, they still need to be disposed of properly.

Coal Power Plants

B9.12 Coal power plant

Approximately 53% of Alberta’s electricity is generated using coal-fired power plants. A simple combustion reaction produces the energy needed.

C(s) + O₂(g) → CO₂(g) + energy

Natural Gas

B9.13 Natural gas furnace

Most homes in Alberta are heated by natural gas furnaces. Again, a combustion reaction is utilized.

CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l) + energy

The production of carbon dioxide by the combustion of coal and methane is of concern to society because of the enhanced greenhouse effect and the resulting changes to Earth’s climate. You will learn more about these concepts in Unit D.

Cellular Respiration

B9.14 Joggers

Your body creates all of its own energy through cellular respiration, which is similar to a hydrocarbon combustion reaction. Later in this section, you will learn more about hydrocarbon combustion reactions.

C₆H₁₂O₆(s) + 6O₂(g) → 6CO₂(g) + 6H₂O(l) + energy

  Read This

  Practice Questions

1. Identify one household process and one industrial or commercial process that use a chemical reaction to produce energy.
   
   
   Check your work.
   

   There are many different examples; here are two. Combusting gasoline in a car produces energy. The combustion of natural gas in a power plant is an example of an industrial or commercial process that uses a chemical reaction to produce energy.
   

  Conclusion

B9.15 Peeling hard-boiled eggs

A tip that you can use to help make eggs easier to peel is to add vinegar to the water when the eggs are being boiled. The chemistry behind this tip has to do with the acidic nature of vinegar and the basic properties of the egg shells. This is just one example of how a little knowledge of chemical reactions can be used to enhance your daily life.

In addition to chemical reactions being important to your daily life, there are also large-scale industrial operations that use chemical reactions to produce useful substances and energy.

  Simulation

Haber–Bosch Ammonia Plant @ AnnenBerg Learner

• Background Information
  
• Procedure
  

Industrial operations are essential for the large-scale production of useful substances, but these operations also need to be profitable. By manipulating conditions, can you successfully run an industrial ammonia plant that utilizes the Haber–Bosch process?

Click on the procedure tab to continue.

1. Click on the play icon to open the virtual lab. The lab can also be accessed at https://www.learner.org/series/chemistry-challenges-and-solutions/control-a-haber-bosch-ammonia-plant/
2. Leave all controls in their default settings and click “RUN.”
   
   What was the Net Profit?
   
   
   Check your work.
   

   –$12 000/day
3. Click “Reset Values.”
4. Increase “Pressure” to 500 atm.
5. Increase “Temperature” to 450 oC.
6. Click “Improved” under “Catalyst.”
7. Click “RUN.”
   
   What was the Net Profit?
   
   
   Check your work.
   

   $24 372/day
8. Click “Reset Values.”
9. Try other combinations of the control panel to try to maximize the net profit. Try manipulating the type of catalyst, purge, flow rate, or cooling.
10. You can track your trials by clicking “See Results.”
    
    What settings provided maximum profits?
    
    
    Check your work.
    

    Answers will vary, but profit will be increased by keeping temperature and pressure high, using the highest quality catalyst, keeping cooling low, increasing flow rate, and increasing purging to a higher percentage. With these settings, you should be able to get daily profits above $34 000.
    

2.5 Assignment

Unit 2 Formative Assessment