Fun Calculations

Practicing the skills of writing chemical formula and calculating relative molecular masses, molar masses and percentage compositions can be a bit, .. well, ... a bit ..... boring (sh, don't tell anyone I said that). But, you can use chemspider to find some interesting molecules for your students to practice their skills on.
ChemSpider is a free chemical structure database run by the Royal Society of Chemistry. It provides access to over 25 million chemical structures, properties and associated information.

Activity:
For each of the molecules below:

1. Use chemspider to find the structural formula.
2. Write the molecular formula..
3. Calculate the relative molecular mass..
4. Calculate the molar mass..
5. Calculate the percentage of carbon present..

Molecules with "interesting names" to practice on:

• olympicene
• ovalene
• performic acid
• traumatic acid
• arabitol
• putrescine
• cadaverine
• nonose 
• syringic acid
• warfarin
• orotic acid
• megaphone
•  moronic acid
• inflatene
• sexithiophene
• arsole
• anol

Further Reading
Calculating Relative Molecular Mass
Molar Mass
Percentage Composition

Amine Scrubbing

Fossil fuel-burning power plants, in particular coal-burning power plants, are a major source of a carbon dioxide, a greenhouse gas. When power plants begin capturing their carbon emissions to reduce greenhouse gases it will be an expensive undertaking. Current technologies use about one-third of the energy generated by power plants to capture greenhouse gas emissions, this is referred to as parasitic energy.

Although no commercial power plants currently capture carbon dioxide on a large scale, a few small-scale and pilot plants do. One commonly used process is known as amine scrubbing in which gas emissions are funneled through an amine bath, which absorbs carbon dioxide from the flue gases. Typical amine baths in use are:

• 32 % by mass aqueous 2-aminoethanol (NH₂-CH₂-CH₂OH) solution
• 25% by mas aqueous 2,2'-Iminodiethanol (HN(CH₂CH₂OH)₂) solution
• 40% by mass bis(2-hydroxyethyl)methylamine (CH₃N (C₂H₄OH)₂₎ solution
• 50% by mass 2-(2-Aminoethoxy)ethanol solution
  

 The amines are then boiled to release the CO₂. Additional energy is required to compress the carbon dioxide so that it can be pumped underground.
The energy needed for this process decreases the amount that can go into making electricity. Calculations show that for a coal-fired power plant, that could amount to approximately 30% of total energy generated.

A group of  scientists from UC Berkeley and EPRI have developed a computer model to calculate energy energy costs of carbon dioxide capture, release and compression, for any material including the amine baths above as well as zeolites (porous materials made of silicon dioxide) and MOFs (metal oxide frameworks).

Reference
Li-Chiang Lin, Adam H. Berger, Richard L. Martin, Jihan Kim, Joseph A. Swisher, Kuldeep Jariwala, Chris H. Rycroft, Abhoyjit S. Bhown, Michael W. Deem, Maciej Haranczyk, Berend Smit. In silico screening of carbon-capture materials. Nature Materials, 2012; DOI: 10.1038/nmat3336

Further Reading:
Greenhouse Gases and the Greenhouse Effect
Combustion of Hydrocarbons
Amines

Percent By Mass (weight) Concentration 
Zeolites


Suggested Study Questions:

1.  Give the name and formula of the four main naturally occurring greenhouse gases.
2. Give the name and formula of four human-induced greenhouse gases.
3. Write a chemical equation for the complete combustion of coal.
4. Anthracite is a type of coal that is made up of about 95% carbon. The combustion of 1g of coal releases about 1000 kJ of energy. Calculate the heat of combustion of anthracite in kJ/mol
5. Write the molecular formula for each of the 4 amines used in amine scrubbing baths.
6. On the structural formula for each of the amines used in amine scrubbers:
   • circle amino groups in blue
   • circle hydroxyl groups in red
7. For a 32% by mass aqueous 2-aminoethanol solution, calculate the mass of  2-aminoethanol present in
   • 1 kg of solution
   • 100 g of solution
   • 1 tonne of solution
   • 2500 mg of solution
8. What is the concentration in mol/L of the1 kg of  a 32% by mass aqueous 2-aminoethanol solution?

 

Saccharin

Saccharin, an "artificial sweetener", is the trade name for the organic compound 1,1-dioxo-1,2-benzothiazol-3-one (also known as benzoic sulfimide). It has been used widely in the production of "diet" foods and drinks because it has effectively no food energy, it passes through the human digestive system without being digested. Saccharin was first discovered by accident in 1878 by Constantin Fahlberg when he was analysing the chemical compounds in coal tar and discovered a sweet-tasting substance on his hands.

Saccharin was produced from toluene in several steps:
1/ chlorosulfonic acid is used to produce two sulfonated isomers of toluene:

2/ The ortho isomer is then separated, and reacted with ammonia to produce the sulfonamide:

3/ The sulfonamide product above undergoes oxidation to produce the carboxylic acid which then cyclicizes to form saccharin:

Further Reading
Molecular Formula
Functional Groups
Structural Isomers - Alkanes
Structural Isomers - Alkenes


Suggested Study Questions

1. Write the molecular formula for
   • toluene
   • saccharin
2. For each of the 3 steps shown in the synthesis of saccharin, circle the site on the reactant molecule where the reaction takes place.
3. In step 3 the carboxylic acid is formed and then the molecule forms a ring (cyclicizes)
   • What functional group is present in a carboxylic acid?
   • Draw the probable structural formula for the carboxylic acid produced in step 3.
4. What functional group is present in an amide? 
5. Toluene is an aromatic compound. Aromatic compounds contain a substituted benzene ring (C₆H₆). Circle the benzene ring  on the structural formula of toluene.
6. Given the formula for chlorosulfonic acid in the article, write the formula for each of the following:
   • fluorosulfonic acid
   • bromosulfonic acid
7. Two structural isomers of  the sulfonated product are shown in step 1. A third structural isomer is also possible. Draw the structural formula of this other isomer.
8. If the para isomer from step 1 reacts with ammonia in a similar manner to the ortho isomer, give the structural formula likely for the compound formed during this reaction.
9. Why do you think the ortho isomer must be separated from the para isomer before step 2?

Bath Bombs

Fizzy bath bombs, the scented balls you place in your bath, are an example of a chemical reaction between an acid and a carbonate.
Below is a simple recipe for making your own bath bombs.

Equipment	Procedure
mixing bowl jar waxed paper 2 tablespoons citric acid 1/4 cup sodium bicarbonate 1/4 teaspoon fragrant oil (eg lavender oil) 3 tablespoons vegetable oil (eg olive oil)	1. Mix sodium bicarbonate and citric acid together in the mixing bowl. 2. Mix fragrant oil and vegetable oil together in the jar. 3. Slowly add contents of jar to mixing bowl while stirring. 4. Form small balls of mixture and place on waxed paper. 5. Allow balls to dry for 1 or 2 days before storing. 6. Add a ball to your bath water and enjoy!

When you drop your bath bomb into water, the process of dissolving the bath bomb allows the sodium bicarbonate and citric acid to react to produce soluble sodium citrate, water and carbon dioxide gas. The bubbles of carbon dioxide given off during the reaction is why the bath bomb fizzes in the water.

The vegetable oil is not soluble in water, so as the sodium bicarbonate and citric acid react, vegetable oil is released into the water forming a thin layer on your skin which can help "moisturize" it. At the same time, the fragrant oil, which is also insoluble in water, is released, so you can smell the scent.

Further Reading
Definitions and Properties of Acids and Bases
Reaction Calculations: Mass and Moles
Limiting Reagents and Reactants in Excess

Suggested Study Questions

1. Sodium bicarbonate is also known as sodium hydrogen carbonate, baking soda, bread soda and cooking soda. Write the chemical formula for sodium bicarbonate.
2. Write a word equation for the reaction between citric acid and sodium bicarbonate.
3. A balanced chemical equation for the reaction between citric acid and sodium bicarbonate is :
   C₅H₇O₅COOH + NaHCO₃ → C₅H₇O₅COO^-Na⁺ + H₂O + CO₂
   Name each of the following compounds:
   • NaHCO₃
   • C₅H₇O₅COOH
   • C₅H₇O₅COO^-Na⁺
   • CO₂
   • H₂O
   
   
4. Write a chemical equation to show citric acid acting as a Bronsted-Lowry acid.
5. Sodium bicarbonate is amphiprotic.Write a chemical equation to show sodium bicarbonate
   • accepting a proton
   • donating a proton.
6. In the reaction between citric acid and sodium bicarbonate, is sodium bicarbonate acting as an acid or a base? Explain your answer. 
7. For the bicarbonate ion, give the formula for its
   • conjugate base
   • conjugate acid 
8. The density of citric acid is about 1.5 g/mL. If a tablespoon has a volume of 15 mL, what mass of citric acid was used in preparing the bath bomb? 
9. Sodium bicarbonate has a density of about 2.2 g/mL and there are 16 tablespoons in 1 cup. What mass of sodium bicarbonate was used to make the bath bomb?
10. For the reaction between citric acid and sodium bicarbonate given the quantities used in the procedure provided above, which reactant is
    • the limiting reagent
    • the reactant in excess
11. Calculate the mass of carbon dioxide you would expect to be released during the reaction between citric acid and sodium bicarbonate as described in the above procedure. 
12. Assuming a temperature of 25^oC and a pressure of 100 kPa, what volume of carbon dioxide gas would be released using the data above? 
13. If the amount of sodium bicarbonate used to make the bath bombs as described above were doubled, what effect would that have on the amount of carbon dioxide produced when the bombs were placed in water?
14. Write an aim for the experiment described above.