1. Why do alkanes and their corresponding alkenes have similar physical properties but very different chemical properties?
They have very similar molecular masses (differing by only approximately 1.008 g - one hydrogen atom) and are hence of the same states at the same temperatures. However, their differing chemical properties are due to the alkenes being unsaturated - that is, they do not have the maximum number of atoms attached to the carbon chain. This is because there is a double bond between two carbon atoms. The double bond opens easily to undergo addition reactions. For example:
CH2=CH2 + HBr → CH3-CH2Br
Alkanes are saturated compounds, therefore cannot participate in addition reactions.
2. Assess the current developements in the use of biopolymer - how am I suppose to structure a response and answer to that question?
Name of biopolymer: Biopol, or poly-β-hydroxybutanoate, or PHB (they're all the same thing). This biopolymer belongs to the category of PHA - poly-β-hydroxyalkanoates.
Structure: CH3-CHOH-CH2-COOH is the monomer. The β means that the hydroxy group is the second carbon away from the carboxylic acid group. The polymer is [ -O-CHCH3-CH2- ]n. (Note: the CH3 in bold is draw below the CH that precedes it)
Production: It is made from the microorganism Alcaligenes Eutrophus. This microorganism is placed in a suitable environment and fed appropriate nutrients. It then begins to multiply. When the desired amount has been reached, one nutrient is restricted (for example, nitrogen) and the microorganism cannot continue to reproduce. Instead, it begins to form the polymer, which it would later store as an energy source. 30-80% of the polymer can be harvested from the dry weight of the microorganism.
Properties: Biopol has extremely similar properties to polypropylene, with the important exception that it is biodegradable.
Uses: Biopol has great potential to be used in the production of products where biodegradability is of great concern. For example, nappies, plastic bottles, plastic bags, wrapping film, hospital supplies and packaging.
Assessment: Although still in the early stages of large-scale production, Biopol has shown great potential to be used in areas where biodegradability is of significance. If there are no great economic concerns, it is likely to successfully replace the current non-biodegradable polypropylene.
3. Please answer the question attached.
Always write an equation: Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2H2O(l)
When no sulfuric acid has been added, the barium hydroxide exists in solution as ions of OH- and Ba2+ and conducts electricity. As sulfuric acid is added, the precipitate BaSO4 is formed. This precipitate does not conduct electricity and therefore the conductivity decreases. At the minimum point of the graph, the titration is at the equivalence point, where the amount of barium hydroxide and sulfuric acid is equal and therefore the products are only the precipitate and water. Assuming water does not conduct electricity*, the precipitate will not conduct and therefore the f(x) = 0. As more sulfuric acid is added, the sulfuric acid reactant is in excess - there is no more barium hydroxide to react with it to form precipitates, therefore the sulfuric acid remains in solution, where it ionises into H+ (technically H3O+) and SO42- and conducts electricity.
* What I don't get is that the conductivity is 0 at one point. The self-ionisation of water allows it to conduct electricity to some extent. There are always small amounts of H3O+ and OH- ions present, so how is it possible that the conductivity is 0 at any time?
